CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>Delboeuf illusion - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy", "wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"f86afe75-c956-4ed7-9e5e-706dea2c8f0e","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Delboeuf_illusion","wgTitle":"Delboeuf illusion","wgCurRevisionId":1206076035,"wgRevisionId":1206076035,"wgArticleId":23003241,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["CS1 French-language sources (fr)","All articles with dead external links","Articles with dead external links from February 2024","Articles with permanently dead external links","Articles with short description","Short description matches Wikidata","Optical illusions"],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Delboeuf_illusion","wgRelevantArticleId":23003241,"wgIsProbablyEditable":true, "wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false,"wgFlaggedRevsParams":{"tags":{"status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":10000,"wgRelatedArticlesCompat":[],"wgCentralAuthMobileDomain":false,"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgWikibaseItemId":"Q1184010","wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics": true,"wgGETopicsMatchModeEnabled":false,"wgGEStructuredTaskRejectionReasonTextInputEnabled":false,"wgGELevelingUpEnabledForUser":false};RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.cite.styles":"ready","skins.vector.search.codex.styles":"ready","skins.vector.styles":"ready","skins.vector.icons":"ready","jquery.makeCollapsible.styles":"ready","ext.wikimediamessages.styles":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","wikibase.client.init":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","mediawiki.page.media","site","mediawiki.page.ready","jquery.makeCollapsible","mediawiki.toc","skins.vector.js","ext.centralNotice.geoIP","ext.centralNotice.startUp","ext.gadget.ReferenceTooltips","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap", "ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming","ext.uls.interface","ext.cx.eventlogging.campaigns","ext.cx.uls.quick.actions","wikibase.client.vector-2022","ext.checkUser.clientHints","ext.growthExperiments.SuggestedEditSession","wikibase.sidebar.tracking"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediaBadges%7Cext.wikimediamessages.styles%7Cjquery.makeCollapsible.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles%7Cwikibase.client.init&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.4"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Delboeuf_illusion.svg/1200px-Delboeuf_illusion.svg.png"> <meta property="og:image:width" content="1200"> <meta property="og:image:height" content="717"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Delboeuf_illusion.svg/800px-Delboeuf_illusion.svg.png"> <meta property="og:image:width" content="800"> <meta property="og:image:height" content="478"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Delboeuf_illusion.svg/640px-Delboeuf_illusion.svg.png"> <meta property="og:image:width" content="640"> <meta property="og:image:height" content="383"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="Delboeuf illusion - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/Delboeuf_illusion"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=Delboeuf_illusion&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/Delboeuf_illusion"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//meta.wikimedia.org" /> <link rel="dns-prefetch" href="//login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Delboeuf_illusion rootpage-Delboeuf_illusion skin-vector-2022 action-view"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Delboeuf+illusion" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Delboeuf+illusion" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Delboeuf+illusion" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Delboeuf+illusion" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Eponym" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Eponym"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Eponym</span> </div> </a> <ul id="toc-Eponym-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Factors" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Factors"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Factors</span> </div> </a> <ul id="toc-Factors-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Dieting_and_food_perception" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Dieting_and_food_perception"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Dieting and food perception</span> </div> </a> <ul id="toc-Dieting_and_food_perception-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Use_in_animal_cognition" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Use_in_animal_cognition"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Use in animal cognition</span> </div> </a> <button aria-controls="toc-Use_in_animal_cognition-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Use in animal cognition subsection</span> </button> <ul id="toc-Use_in_animal_cognition-sublist" class="vector-toc-list"> <li id="toc-Primates" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Primates"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Primates</span> </div> </a> <ul id="toc-Primates-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Dogs" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Dogs"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Dogs</span> </div> </a> <ul id="toc-Dogs-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Fish" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Fish"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Fish</span> </div> </a> <ul id="toc-Fish-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Reptiles" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Reptiles"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.4</span> <span>Reptiles</span> </div> </a> <ul id="toc-Reptiles-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Delboeuf illusion</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 7 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-7" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">7 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Delboeuf-T%C3%A4uschung" title="Delboeuf-Täuschung – German" lang="de" hreflang="de" data-title="Delboeuf-Täuschung" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Ilusi%C3%B3n_de_Delboeuf" title="Ilusión de Delboeuf – Spanish" lang="es" hreflang="es" data-title="Ilusión de Delboeuf" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%AE%D8%B7%D8%A7%DB%8C_%D8%AF%DB%8C%D8%AF_%D8%AF%D9%84%D8%A8%D9%88%D9%81" title="خطای دید دلبوف – Persian" lang="fa" hreflang="fa" data-title="خطای دید دلبوف" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%83%87%E3%83%AB%E3%83%96%E3%83%BC%E3%83%95%E9%8C%AF%E8%A6%96" title="デルブーフ錯視 – Japanese" lang="ja" hreflang="ja" data-title="デルブーフ錯視" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Z%C5%82udzenie_Delboeufa" title="Złudzenie Delboeufa – Polish" lang="pl" hreflang="pl" data-title="Złudzenie Delboeufa" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%98%D0%BB%D0%BB%D1%8E%D0%B7%D0%B8%D1%8F_%D0%94%D0%B5%D0%BB%D1%8C%D0%B1%D1%91%D1%84%D0%B0" title="Иллюзия Дельбёфа – Russian" lang="ru" hreflang="ru" data-title="Иллюзия Дельбёфа" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/%E1%BA%A2o_gi%C3%A1c_Delboeuf" title="Ảo giác Delboeuf – Vietnamese" lang="vi" hreflang="vi" data-title="Ảo giác Delboeuf" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q1184010#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Delboeuf_illusion" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:Delboeuf_illusion" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Delboeuf_illusion"><span>Read</span></a></li><li id="ca-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Delboeuf_illusion&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Delboeuf_illusion&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Delboeuf_illusion"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Delboeuf_illusion&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Delboeuf_illusion&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Delboeuf_illusion" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Delboeuf_illusion" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q"><span>Special pages</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Delboeuf_illusion&oldid=1206076035" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Delboeuf_illusion&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=Delboeuf_illusion&id=1206076035&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FDelboeuf_illusion"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FDelboeuf_illusion"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=Delboeuf_illusion&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Delboeuf_illusion&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="wb-otherproject-link wb-otherproject-commons mw-list-item"><a href="https://commons.wikimedia.org/wiki/Category:Delboeuf_illusion" hreflang="en"><span>Wikimedia Commons</span></a></li><li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q1184010" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Optical illusion</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Delboeuf_illusion.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Delboeuf_illusion.svg/220px-Delboeuf_illusion.svg.png" decoding="async" width="220" height="132" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Delboeuf_illusion.svg/330px-Delboeuf_illusion.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/76/Delboeuf_illusion.svg/440px-Delboeuf_illusion.svg.png 2x" data-file-width="920" data-file-height="550" /></a><figcaption>Though the two circled dark discs are the same size, the left disc seems smaller than the right one.</figcaption></figure> <p>The <b>Delboeuf illusion</b> is an <a href="/wiki/Optical_illusion" title="Optical illusion">optical illusion</a> of relative size perception: In the best-known version of the illusion, two discs of identical size have been placed near to each other and one is surrounded by a <a href="/wiki/Annulus_(mathematics)" title="Annulus (mathematics)">ring</a>; the surrounded disc then appears larger than the non-surrounded disc if the ring is close, while appearing smaller than the non-surrounded disc if the ring is distant. A 2005 study suggests it is caused by the same visual processes that cause the <a href="/wiki/Ebbinghaus_illusion" title="Ebbinghaus illusion">Ebbinghaus illusion</a>.<sup id="cite_ref-Roberts_1-0" class="reference"><a href="#cite_note-Roberts-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Eponym">Eponym</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=1" title="Edit section: Eponym"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The illusion was named for the Belgian philosopher, mathematician, experimental psychologist, hypnotist, and psychophysicist <a href="/wiki/Joseph_Delboeuf" title="Joseph Delboeuf">Joseph Remi Leopold Delboeuf</a> (1831–1896), who discovered it in 1865.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Factors">Factors</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=2" title="Edit section: Factors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>According to Girgus and Coren (1982) the Delboeuf illusion uses both <a href="/wiki/Assimilation_and_contrast_effects" title="Assimilation and contrast effects">assimilation and contrast</a> as elements in its perception distortion.<sup id="cite_ref-:0_3-0" class="reference"><a href="#cite_note-:0-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Assimilation is the predominant factor in the disc in the smaller outer ring (the example on the right in the image above). Girgus and Coren mentioned that this inner disc “tends to be overestimated” when compared to a regular disc without the additional concentric circle.<sup id="cite_ref-:0_3-1" class="reference"><a href="#cite_note-:0-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> As the two circles are so close, they are perceived as a pair and the inner circle is overestimated. </p><p>The circle on the left however, will often appear smaller when compared to a simple circle of the same size. This is attributed to the contrast effect. The distance between the circles causes them to be perceived as separate and contrasting. The larger-circumference ring dwarfs the smaller central disc and causes it to be perceived as smaller.<sup id="cite_ref-:0_3-2" class="reference"><a href="#cite_note-:0-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>After a few minutes of looking at this illusion, the illusory effects diminish for human subjects.<sup id="cite_ref-:0_3-3" class="reference"><a href="#cite_note-:0-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>Studies regarding variations of the Delboeuf illusion found that when the outer circle is incomplete, the illusion is not as potent. When an additional circle was added surrounding the original two, the effect of the illusion was increased.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Dieting_and_food_perception">Dieting and food perception</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=3" title="Edit section: Dieting and food perception"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 2012, Ittersum and Wansink published a study that hinted to the Delboeuf illusion as a factor in increased food servings. The study tested three different bowl diameters and measured how individuals served themselves differently depending on the bowl's diameter. The results showed that consumers poured 9.9% more soup in larger bowls, and 8.2% less in smaller bowls, as compared to the control bowls. It was mentioned that this reaction could be driven by the Delboeuf illusion.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>This illusion in connection to food however appears to be nuanced: Zitron-Emanuel and Ganel (2018) highlighted how effects of the Delboeuf illusion, when related to food items, is less potent when the participants are experiencing mild hunger. These researchers suggest that these findings are potential grounds for mitigating the use of the Delboeuf illusion as a dieting aid.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Use_in_animal_cognition">Use in animal cognition</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=4" title="Edit section: Use in animal cognition"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Delboeuf illusion (often in connection with the <a href="/wiki/Ebbinghaus_illusion" title="Ebbinghaus illusion">Ebbinghaus illusion</a>) has been used with great frequency in testing animal perception, since the ability to discern size seems highly relevant for many aspects of survival, particularly regarding food. The perception of the Delboeuf illusion differs greatly depending on the species. </p> <div class="mw-heading mw-heading3"><h3 id="Primates">Primates</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=5" title="Edit section: Primates"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Parrish & Beran (2014) found that <a href="/wiki/Chimpanzee" title="Chimpanzee">chimpanzees</a> would regularly select food platters that contained more food. Further testing showed that when chimpanzees were offered food on small and large plates, as they often picked the food on the smaller plate, even when the amounts were the same. This was discussed as a sign of the chimpanzee’s susceptibility to the Delboeuf illusion.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>A later study showed that <a href="/wiki/Capuchin_monkey" title="Capuchin monkey">capuchin</a> and <a href="/wiki/Rhesus_macaque" title="Rhesus macaque">rhesus monkeys</a>, however, were unaffected by the illusion when asked to discriminate between the two circles. In contrast, when the illusion was later presented to the monkeys as part of an absolute classification task (deciding if the circles were "big" or "small"), both species reacted to the illusion and made selections that were much like the selections made by humans and chimpanzees.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>An attempt to run tests of portion discrimination in connection to the Delboeuf illusion on <a href="/wiki/Ring-tailed_lemur" title="Ring-tailed lemur">ring-tailed lemurs</a> was unsuccessful; the lemurs' meal selections were not increased by a statistically significant degree by larger food portions, unless one option was nearly 40% larger.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Dogs">Dogs</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=6" title="Edit section: Dogs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Miletto-Petrazzini, Bisazza and Agrillo (2016) replicated the study conducted by Parrish and Beran (2014) but used dogs as the participants instead of chimpanzees. In this study, the dogs were allowed to select whichever food portion appeared larger as presented on larger and smaller plates. The response however was reversed from what humans usually exhibit: Dogs selected the meal presented on the larger plate most often. The authors went on to discuss how this may hint towards the dogs' reactions to the Delboeuf illusion as a matter of <a href="/wiki/Assimilation_and_contrast_effects" title="Assimilation and contrast effects">assimilated learning</a>.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Fish">Fish</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=7" title="Edit section: Fish"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Fish have been repeatedly studied as well to understand if they perceive the Delboeuf illusion. Fish trained to select larger center circles for reward, responded to the illusion differently depending on the species of fish. A 2008 study of <a href="/wiki/Damselfish" title="Damselfish">damselfish</a> illustrated that damselfish responded to variations of the Delboeuf illusion in a similar ways to humans and dolphins,<sup id="cite_ref-:1_11-0" class="reference"><a href="#cite_note-:1-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> while <a href="/wiki/Guppy" title="Guppy">guppies</a> responded in reverse, selecting the circles with the larger <a href="/wiki/Annulus_(mathematics)" title="Annulus (mathematics)">annulus</a>.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Hemiscylliidae" title="Hemiscylliidae">bamboo sharks</a> did not generally make selections significantly higher than chance during the testing, and only showed preference to larger diagrams in general.<sup id="cite_ref-:1_11-1" class="reference"><a href="#cite_note-:1-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Reptiles">Reptiles</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=8" title="Edit section: Reptiles"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Pogona" title="Pogona">Bearded dragons</a> and <a href="/wiki/Red-footed_tortoise" title="Red-footed tortoise">red-footed tortoise</a> were both studied to understand if these species can perceive the Delboeuf illusion. Bearded dragons showed action that suggests that they perceive the illusion in a way similar to humans. The tortoises however, showed no preference to larger portions (a similar problem found in the study of ring-tailed lemurs) and were thus not testable by the method that had been outlined by the test designers.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Delboeuf_illusion&action=edit&section=9" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 25em;"> <ol class="references"> <li id="cite_note-Roberts-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-Roberts_1-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFRobertsHarrisYates2005" class="citation journal cs1">Roberts B, Harris MG, Yates TA (2005). "The roles of inducer size and distance in the Ebbinghaus illusion (Titchener circles)". <i>Perception</i>. <b>34</b> (7): 847–56. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1068%2Fp5273">10.1068/p5273</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/16124270">16124270</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:26626773">26626773</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Perception&rft.atitle=The+roles+of+inducer+size+and+distance+in+the+Ebbinghaus+illusion+%28Titchener+circles%29&rft.volume=34&rft.issue=7&rft.pages=847-56&rft.date=2005&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A26626773%23id-name%3DS2CID&rft_id=info%3Apmid%2F16124270&rft_id=info%3Adoi%2F10.1068%2Fp5273&rft.aulast=Roberts&rft.aufirst=B&rft.au=Harris%2C+MG&rft.au=Yates%2C+TA&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDelboeuf1865" class="citation journal cs1 cs1-prop-foreign-lang-source">Delboeuf, Franz Joseph (1865). "Note sur certaines illusions d'optique: Essai d'une théorie psychophysique de la maniere dont l'oeil apprécie les distances et les angles". <i>Bulletins de l'Académie Royale des Sciences, Lettres et Beaux-Arts de Belgique</i> (in French). <b>19</b>: 195–216.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Bulletins+de+l%27Acad%C3%A9mie+Royale+des+Sciences%2C+Lettres+et+Beaux-Arts+de+Belgique&rft.atitle=Note+sur+certaines+illusions+d%27optique%3A+Essai+d%27une+th%C3%A9orie+psychophysique+de+la+maniere+dont+l%27oeil+appr%C3%A9cie+les+distances+et+les+angles&rft.volume=19&rft.pages=195-216&rft.date=1865&rft.aulast=Delboeuf&rft.aufirst=Franz+Joseph&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-:0-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_3-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:0_3-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-:0_3-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGirgusCoren1982" class="citation journal cs1">Girgus, Joan S.; Coren, Stanley (1982-11-01). <a rel="nofollow" class="external text" href="https://doi.org/10.3758%2FBF03204210">"Assimilation and contrast illusions: Differences in plasticity"</a>. <i>Perception & Psychophysics</i>. <b>32</b> (6): 555–561. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3758%2FBF03204210">10.3758/BF03204210</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1532-5962">1532-5962</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/7167354">7167354</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Perception+%26+Psychophysics&rft.atitle=Assimilation+and+contrast+illusions%3A+Differences+in+plasticity&rft.volume=32&rft.issue=6&rft.pages=555-561&rft.date=1982-11-01&rft.issn=1532-5962&rft_id=info%3Apmid%2F7167354&rft_id=info%3Adoi%2F10.3758%2FBF03204210&rft.aulast=Girgus&rft.aufirst=Joan+S.&rft.au=Coren%2C+Stanley&rft_id=https%3A%2F%2Fdoi.org%2F10.3758%252FBF03204210&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWeintraubSchneck1986" class="citation journal cs1">Weintraub, Daniel J.; Schneck, Michael K. (1986-05-01). <a rel="nofollow" class="external text" href="https://doi.org/10.3758%2FBF03203010">"Fragments of Delboeuf and Ebbinghaus illusions: Contour / context explorations of misjudged circle size"</a>. <i>Perception & Psychophysics</i>. <b>40</b> (3): 147–158. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3758%2FBF03203010">10.3758/BF03203010</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1532-5962">1532-5962</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/3774497">3774497</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Perception+%26+Psychophysics&rft.atitle=Fragments+of+Delboeuf+and+Ebbinghaus+illusions%3A+Contour+%2F+context+explorations+of+misjudged+circle+size&rft.volume=40&rft.issue=3&rft.pages=147-158&rft.date=1986-05-01&rft.issn=1532-5962&rft_id=info%3Apmid%2F3774497&rft_id=info%3Adoi%2F10.3758%2FBF03203010&rft.aulast=Weintraub&rft.aufirst=Daniel+J.&rft.au=Schneck%2C+Michael+K.&rft_id=https%3A%2F%2Fdoi.org%2F10.3758%252FBF03203010&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFvan_IttersumWansink2012" class="citation journal cs1">van Ittersum, Koert; Wansink, Brian (2012-08-01). <a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F662615">"Plate size and color suggestibility: The Delboeuf illusion's bias on serving and eating behavior"</a>. <i>Journal of Consumer Research</i>. <b>39</b> (2): 215–228. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F662615">10.1086/662615</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0093-5301">0093-5301</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Consumer+Research&rft.atitle=Plate+size+and+color+suggestibility%3A+The+Delboeuf+illusion%27s+bias+on+serving+and+eating+behavior&rft.volume=39&rft.issue=2&rft.pages=215-228&rft.date=2012-08-01&rft_id=info%3Adoi%2F10.1086%2F662615&rft.issn=0093-5301&rft.aulast=van+Ittersum&rft.aufirst=Koert&rft.au=Wansink%2C+Brian&rft_id=https%3A%2F%2Fdoi.org%2F10.1086%252F662615&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFZitron-EmanuelGanel2018" class="citation journal cs1">Zitron-Emanuel, Noa; Ganel, Tzvi (1 September 2018). "Food deprivation reduces the susceptibility to size-contrast illusions". <i>Appetite</i>. <b>128</b>: 138–144. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.appet.2018.06.006">10.1016/j.appet.2018.06.006</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1095-8304">1095-8304</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/29885383">29885383</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:47008687">47008687</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Appetite&rft.atitle=Food+deprivation+reduces+the+susceptibility+to+size-contrast+illusions&rft.volume=128&rft.pages=138-144&rft.date=2018-09-01&rft.issn=1095-8304&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A47008687%23id-name%3DS2CID&rft_id=info%3Apmid%2F29885383&rft_id=info%3Adoi%2F10.1016%2Fj.appet.2018.06.006&rft.aulast=Zitron-Emanuel&rft.aufirst=Noa&rft.au=Ganel%2C+Tzvi&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFParrishBeran2014" class="citation journal cs1">Parrish, Audrey E.; Beran, Michael J. (2014-03-01). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3865074">"When less is more: like humans, chimpanzees (<i>Pan troglodytes</i>) misperceive food amounts based on plate size"</a>. <i>Animal Cognition</i>. <b>17</b> (2): 427–434. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs10071-013-0674-3">10.1007/s10071-013-0674-3</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1435-9456">1435-9456</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3865074">3865074</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/23949698">23949698</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Animal+Cognition&rft.atitle=When+less+is+more%3A+like+humans%2C+chimpanzees+%28Pan+troglodytes%29+misperceive+food+amounts+based+on+plate+size&rft.volume=17&rft.issue=2&rft.pages=427-434&rft.date=2014-03-01&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3865074%23id-name%3DPMC&rft.issn=1435-9456&rft_id=info%3Apmid%2F23949698&rft_id=info%3Adoi%2F10.1007%2Fs10071-013-0674-3&rft.aulast=Parrish&rft.aufirst=Audrey+E.&rft.au=Beran%2C+Michael+J.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3865074&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFParrishBrosnanBeran2015" class="citation journal cs1">Parrish, Audrey E.; Brosnan, Sarah F.; Beran, Michael J. (October 2015). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4594174">"Do you see what I see? A comparative investigation of the Delboeuf illusion in humans (<i>Homo sapiens</i>), rhesus monkeys (<i>Macaca mulatta</i>) and capuchin monkeys (<i>Cebus apella</i>)"</a>. <i>Journal of Experimental Psychology: Animal Learning and Cognition</i>. <b>41</b> (4): 395–405. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1037%2Fxan0000078">10.1037/xan0000078</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/2329-8456">2329-8456</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4594174">4594174</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/26322505">26322505</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Experimental+Psychology%3A+Animal+Learning+and+Cognition&rft.atitle=Do+you+see+what+I+see%3F+A+comparative+investigation+of+the+Delboeuf+illusion+in+humans+%28Homo+sapiens%29%2C+rhesus+monkeys+%28Macaca+mulatta%29+and+capuchin+monkeys+%28Cebus+apella%29&rft.volume=41&rft.issue=4&rft.pages=395-405&rft.date=2015-10&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC4594174%23id-name%3DPMC&rft.issn=2329-8456&rft_id=info%3Apmid%2F26322505&rft_id=info%3Adoi%2F10.1037%2Fxan0000078&rft.aulast=Parrish&rft.aufirst=Audrey+E.&rft.au=Brosnan%2C+Sarah+F.&rft.au=Beran%2C+Michael+J.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC4594174&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://article.php/?id=1101">"Preliminary study to investigate the Delboeuf illusion in ring-tailed lemurs (<i>Lemur catta</i>): Methodological challenges"</a>. <i>Animal Behavior and Cognition</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2020-04-04</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Animal+Behavior+and+Cognition&rft.atitle=Preliminary+study+to+investigate+the+Delboeuf+illusion+in+ring-tailed+lemurs+%28Lemur+catta%29%3A+Methodological+challenges&rft_id=http%3A%2F%2Farticle.php%2F%3Fid%3D1101&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span><sup class="noprint Inline-Template"><span style="white-space: nowrap;">[<i><a href="/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot"><span title=" Dead link tagged February 2024">permanent dead link</span></a></i><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span>]</span></sup></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMiletto_PetrazziniBisazzaAgrillo2017" class="citation journal cs1">Miletto Petrazzini, Maria Elena; Bisazza, Angelo; Agrillo, Christian (2017-05-01). "Do domestic dogs (<i>Canis lupus familiaris</i>) perceive the Delboeuf illusion?". <i>Animal Cognition</i>. <b>20</b> (3): 427–434. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs10071-016-1066-2">10.1007/s10071-016-1066-2</a>. <a href="/wiki/Hdl_(identifier)" class="mw-redirect" title="Hdl (identifier)">hdl</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://hdl.handle.net/11577%2F3222731">11577/3222731</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1435-9456">1435-9456</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/27999956">27999956</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:254142505">254142505</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Animal+Cognition&rft.atitle=Do+domestic+dogs+%28Canis+lupus+familiaris%29+perceive+the+Delboeuf+illusion%3F&rft.volume=20&rft.issue=3&rft.pages=427-434&rft.date=2017-05-01&rft_id=info%3Ahdl%2F11577%2F3222731&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A254142505%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1007%2Fs10071-016-1066-2&rft.issn=1435-9456&rft_id=info%3Apmid%2F27999956&rft.aulast=Miletto+Petrazzini&rft.aufirst=Maria+Elena&rft.au=Bisazza%2C+Angelo&rft.au=Agrillo%2C+Christian&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-:1-11"><span class="mw-cite-backlink">^ <a href="#cite_ref-:1_11-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:1_11-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFussSchluessel2017" class="citation journal cs1">Fuss, Theodora; Schluessel, Vera (2017-08-01). <a rel="nofollow" class="external text" href="http://www.sciencedirect.com/science/article/pii/S0944200616301246">"The Ebbinghaus illusion in the gray bamboo shark (<i>Chiloscyllium griseum</i>) in comparison to the teleost damselfish (<i>Chromis chromis</i>)"</a>. <i>Zoology</i>. <b>123</b>: 16–29. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.zool.2017.05.006">10.1016/j.zool.2017.05.006</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0944-2006">0944-2006</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/28712674">28712674</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Zoology&rft.atitle=The+Ebbinghaus+illusion+in+the+gray+bamboo+shark+%28Chiloscyllium+griseum%29+in+comparison+to+the+teleost+damselfish+%28Chromis+chromis%29&rft.volume=123&rft.pages=16-29&rft.date=2017-08-01&rft.issn=0944-2006&rft_id=info%3Apmid%2F28712674&rft_id=info%3Adoi%2F10.1016%2Fj.zool.2017.05.006&rft.aulast=Fuss&rft.aufirst=Theodora&rft.au=Schluessel%2C+Vera&rft_id=http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0944200616301246&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLucon-XiccatoSantacàMiletto_PetrazziniAgrillo2019" class="citation journal cs1">Lucon-Xiccato, Tyrone; Santacà, Maria; Miletto Petrazzini, Maria Elena; Agrillo, Christian; Dadda, Marco (2019-05-01). "Guppies, <i>Poecilia reticulata</i>, perceive a reversed Delboeuf illusion". <i>Animal Cognition</i>. <b>22</b> (3): 291–303. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs10071-019-01237-6">10.1007/s10071-019-01237-6</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1435-9456">1435-9456</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/30848385">30848385</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:254140496">254140496</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Animal+Cognition&rft.atitle=Guppies%2C+Poecilia+reticulata%2C+perceive+a+reversed+Delboeuf+illusion&rft.volume=22&rft.issue=3&rft.pages=291-303&rft.date=2019-05-01&rft.issn=1435-9456&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A254140496%23id-name%3DS2CID&rft_id=info%3Apmid%2F30848385&rft_id=info%3Adoi%2F10.1007%2Fs10071-019-01237-6&rft.aulast=Lucon-Xiccato&rft.aufirst=Tyrone&rft.au=Santac%C3%A0%2C+Maria&rft.au=Miletto+Petrazzini%2C+Maria+Elena&rft.au=Agrillo%2C+Christian&rft.au=Dadda%2C+Marco&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSantacà,_Maria_MilettoPetrazzini,_Maria_ElenaAgrillo,_ChristianWilkinson,_Anna2019" class="citation journal cs1">Santacà, Maria Miletto; Petrazzini, Maria Elena; Agrillo, Christian; Wilkinson, Anna (2019). <a rel="nofollow" class="external text" href="https://psycnet.apa.org/record/2019-15632-001">"Can reptiles perceive visual illusions? Delboeuf illusion in red-footed tortoise (<i>Chelonoidis carbonaria</i>) and bearded dragon (<i>Pogona vitticeps</i>)"</a>. <i>Journal of Comparative Psychology</i>. <b>133</b> (4): 419–427. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1037%2Fcom0000176">10.1037/com0000176</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/30896231">30896231</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:84842383">84842383</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2020-04-04</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Comparative+Psychology&rft.atitle=Can+reptiles+perceive+visual+illusions%3F+Delboeuf+illusion+in+red-footed+tortoise+%28Chelonoidis+carbonaria%29+and+bearded+dragon+%28Pogona+vitticeps%29&rft.volume=133&rft.issue=4&rft.pages=419-427&rft.date=2019&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A84842383%23id-name%3DS2CID&rft_id=info%3Apmid%2F30896231&rft_id=info%3Adoi%2F10.1037%2Fcom0000176&rft.au=Santac%C3%A0%2C+Maria+Miletto&rft.au=Petrazzini%2C+Maria+Elena&rft.au=Agrillo%2C+Christian&rft.au=Wilkinson%2C+Anna&rft_id=https%3A%2F%2Fpsycnet.apa.org%2Frecord%2F2019-15632-001&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADelboeuf+illusion" class="Z3988"></span></span> </li> </ol></div> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Optical_illusions_(list)" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Optical_illusions" title="Template:Optical illusions"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Optical_illusions" title="Template talk:Optical illusions"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Optical_illusions" title="Special:EditPage/Template:Optical illusions"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Optical_illusions_(list)" style="font-size:114%;margin:0 4em"><a href="/wiki/Optical_illusion" title="Optical illusion">Optical illusions</a> (<a href="/wiki/List_of_optical_illusions" title="List of optical illusions">list</a>)</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Illusions</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Afterimage" title="Afterimage">Afterimage</a></li> <li><a href="/wiki/Ambigram" title="Ambigram">Ambigram</a></li> <li><a href="/wiki/Ambiguous_image" title="Ambiguous image">Ambiguous image</a></li> <li><a href="/wiki/Ames_room" title="Ames room">Ames room</a></li> <li><a href="/wiki/Autostereogram" title="Autostereogram">Autostereogram</a></li> <li><a href="/wiki/Barberpole_illusion" title="Barberpole illusion">Barberpole</a></li> <li><a href="/wiki/Bezold_effect" title="Bezold effect">Bezold</a></li> <li><a href="/wiki/Caf%C3%A9_wall_illusion" title="Café wall illusion">Café wall</a></li> <li><a href="/wiki/Checker_shadow_illusion" title="Checker shadow illusion">Checker shadow</a></li> <li><a href="/wiki/Chubb_illusion" title="Chubb illusion">Chubb</a></li> <li><a href="/wiki/Cornsweet_illusion" title="Cornsweet illusion">Cornsweet</a></li> <li><a class="mw-selflink selflink">Delboeuf</a></li> <li><a href="/wiki/Ebbinghaus_illusion" title="Ebbinghaus illusion">Ebbinghaus</a></li> <li><a href="/wiki/Ehrenstein_illusion" title="Ehrenstein illusion">Ehrenstein</a></li> <li><a href="/wiki/Flash_lag_illusion" title="Flash lag illusion">Flash lag</a></li> <li><a href="/wiki/Fraser_spiral_illusion" title="Fraser spiral illusion">Fraser spiral</a></li> <li><a href="/wiki/Gravity_hill" title="Gravity hill">Gravity hill</a></li> <li><a href="/wiki/Grid_illusion" title="Grid illusion">Grid</a></li> <li><a href="/wiki/Hering_illusion" title="Hering illusion">Hering</a></li> <li><a href="/wiki/Impossible_trident" title="Impossible trident">Impossible trident</a></li> <li><a href="/wiki/Irradiation_illusion" title="Irradiation illusion">Irradiation</a></li> <li><a href="/wiki/Jastrow_illusion" title="Jastrow illusion">Jastrow</a></li> <li><a href="/wiki/Lilac_chaser" title="Lilac chaser">Lilac chaser</a></li> <li><a href="/wiki/Mach_bands" title="Mach bands">Mach bands</a></li> <li><a href="/wiki/McCollough_effect" title="McCollough effect">McCollough</a></li> <li><a href="/wiki/M%C3%BCller-Lyer_illusion" title="Müller-Lyer illusion">Müller-Lyer</a></li> <li><a href="/wiki/Necker_cube" title="Necker cube">Necker cube</a></li> <li><a href="/wiki/Oppel-Kundt_illusion" title="Oppel-Kundt illusion">Oppel-Kundt</a></li> <li><a href="/wiki/Orbison_illusion" title="Orbison illusion">Orbison</a></li> <li><a href="/wiki/Penrose_stairs" title="Penrose stairs">Penrose stairs</a></li> <li><a href="/wiki/Penrose_triangle" title="Penrose triangle">Penrose triangle</a></li> <li><a href="/wiki/Peripheral_drift_illusion" title="Peripheral drift illusion">Peripheral drift</a></li> <li><a href="/wiki/Poggendorff_illusion" title="Poggendorff illusion">Poggendorff</a></li> <li><a href="/wiki/Ponzo_illusion" title="Ponzo illusion">Ponzo</a></li> <li><a href="/wiki/Rubin_vase" title="Rubin vase">Rubin vase</a></li> <li><a href="/wiki/Sander_illusion" title="Sander illusion">Sander</a></li> <li><a href="/wiki/Schroeder_stairs" title="Schroeder stairs">Schroeder stairs</a></li> <li><a href="/wiki/Shepard_tables" title="Shepard tables">Shepard tables</a></li> <li><a href="/wiki/Spinning_dancer" title="Spinning dancer">Spinning dancer</a></li> <li><a href="/wiki/Ternus_illusion" title="Ternus illusion">Ternus</a></li> <li><a href="/wiki/Vertical%E2%80%93horizontal_illusion" title="Vertical–horizontal illusion">Vertical–horizontal</a></li> <li><a href="/wiki/White%27s_illusion" title="White's illusion">White's</a></li> <li><a href="/wiki/Wundt_illusion" title="Wundt illusion">Wundt</a></li> <li><a href="/wiki/Z%C3%B6llner_illusion" title="Zöllner illusion">Zöllner</a></li></ul> </div></td><td class="noviewer navbox-image" rowspan="3" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/File:Optical_Illustion-Ambiguous_Patterns.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/51/Optical_Illustion-Ambiguous_Patterns.svg/30px-Optical_Illustion-Ambiguous_Patterns.svg.png" decoding="async" width="30" height="112" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/51/Optical_Illustion-Ambiguous_Patterns.svg/45px-Optical_Illustion-Ambiguous_Patterns.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/51/Optical_Illustion-Ambiguous_Patterns.svg/60px-Optical_Illustion-Ambiguous_Patterns.svg.png 2x" data-file-width="117" data-file-height="438" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Popular culture</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Op_art" title="Op art">Op art</a></li> <li><i><a href="/wiki/Trompe-l%27%C5%93il" title="Trompe-l'œil">Trompe-l'œil</a></i></li> <li><i><a href="/wiki/Spectropia" title="Spectropia">Spectropia</a></i> (1864 book)</li> <li><i><a href="/wiki/Ascending_and_Descending" title="Ascending and Descending">Ascending and Descending</a></i> (1960 drawing)</li> <li><i><a href="/wiki/Waterfall_(M._C._Escher)" title="Waterfall (M. C. Escher)">Waterfall</a></i> (1961 drawing)</li> <li><i><a href="/wiki/The_dress" title="The dress">The dress</a></i> (2015 photograph)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Accidental_viewpoint" title="Accidental viewpoint">Accidental viewpoint</a></li> <li><a href="/wiki/Auditory_illusion" title="Auditory illusion">Auditory illusions</a></li> <li><a href="/wiki/Illusion" title="Illusion">Illusions</a></li> <li><a href="/wiki/Tactile_illusion" title="Tactile illusion">Tactile illusions</a></li> <li><a href="/wiki/Time_perception" title="Time perception">Temporal illusion</a></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Delboeuf_illusion&oldid=1206076035">https://en.wikipedia.org/w/index.php?title=Delboeuf_illusion&oldid=1206076035</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Category</a>: <ul><li><a href="/wiki/Category:Optical_illusions" title="Category:Optical illusions">Optical illusions</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:CS1_French-language_sources_(fr)" title="Category:CS1 French-language sources (fr)">CS1 French-language sources (fr)</a></li><li><a href="/wiki/Category:All_articles_with_dead_external_links" title="Category:All articles with dead external links">All articles with dead external links</a></li><li><a href="/wiki/Category:Articles_with_dead_external_links_from_February_2024" title="Category:Articles with dead external links from February 2024">Articles with dead external links from February 2024</a></li><li><a href="/wiki/Category:Articles_with_permanently_dead_external_links" title="Category:Articles with permanently dead external links">Articles with permanently dead external links</a></li><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 11 February 2024, at 04:32<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. By using this site, you agree to the <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Terms_of_Use" class="extiw" title="foundation:Special:MyLanguage/Policy:Terms of Use">Terms of Use</a> and <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy" class="extiw" title="foundation:Special:MyLanguage/Policy:Privacy policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a rel="nofollow" class="external text" href="https://wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Delboeuf_illusion&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://wikimediafoundation.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/static/images/footer/wikimedia-button.svg" width="84" height="29" alt="Wikimedia Foundation" loading="lazy"></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/w/resources/assets/poweredby_mediawiki.svg" alt="Powered by MediaWiki" width="88" height="31" loading="lazy"></a></li> </ul> </footer> </div> </div> </div> <div class="vector-settings" id="p-dock-bottom"> <ul></ul> </div><script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.main-6b7f745dd4-w9mpz","wgBackendResponseTime":164,"wgPageParseReport":{"limitreport":{"cputime":"0.297","walltime":"0.366","ppvisitednodes":{"value":1231,"limit":1000000},"postexpandincludesize":{"value":49176,"limit":2097152},"templateargumentsize":{"value":1319,"limit":2097152},"expansiondepth":{"value":17,"limit":100},"expensivefunctioncount":{"value":2,"limit":500},"unstrip-depth":{"value":1,"limit":20},"unstrip-size":{"value":62734,"limit":5000000},"entityaccesscount":{"value":0,"limit":400},"timingprofile":["100.00% 317.019 1 -total"," 59.28% 187.913 1 Template:Reflist"," 37.50% 118.875 12 Template:Cite_journal"," 20.90% 66.270 1 Template:Optical_illusions"," 20.10% 63.734 1 Template:Navbox"," 17.38% 55.088 1 Template:Short_description"," 12.67% 40.163 1 Template:Dead_link"," 11.06% 35.078 1 Template:Fix"," 10.96% 34.748 2 Template:Pagetype"," 9.51% 30.158 2 Template:Category_handler"]},"scribunto":{"limitreport-timeusage":{"value":"0.188","limit":"10.000"},"limitreport-memusage":{"value":5040867,"limit":52428800}},"cachereport":{"origin":"mw-api-ext.codfw.main-744c7589dd-gjpn2","timestamp":"20241125092213","ttl":2592000,"transientcontent":false}}});});</script> <script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"Article","name":"Delboeuf illusion","url":"https:\/\/en.wikipedia.org\/wiki\/Delboeuf_illusion","sameAs":"http:\/\/www.wikidata.org\/entity\/Q1184010","mainEntity":"http:\/\/www.wikidata.org\/entity\/Q1184010","author":{"@type":"Organization","name":"Contributors to Wikimedia projects"},"publisher":{"@type":"Organization","name":"Wikimedia Foundation, Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2009-05-29T14:35:26Z","dateModified":"2024-02-11T04:32:56Z","image":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/7\/76\/Delboeuf_illusion.svg","headline":"optical illusion"}</script> </body> </html>