title: Object knowledge modulates colour appearance.
abstract: We investigated the memory colour effect for colour diagnostic artificial objects. Since knowledge about these objects and their colours has been learned in everyday life, these stimuli allow the investigation of the influence of acquired object knowledge on colour appearance. These investigations are relevant for questions about how object and colour information in high-level vision interact as well as for research about the influence of learning and experience on perception in general. In order to identify suitable artificial objects, we developed a reaction time paradigm that measures (subjective) colour diagnosticity. In the main experiment, participants adjusted sixteen such objects to their typical colour as well as to grey. If the achromatic object appears in its typical colour, then participants should adjust it to the opponent colour in order to subjectively perceive it as grey. We found that knowledge about the typical colour influences the colour appearance of artificial objects. This effect was particularly strong along the daylight axis.
authors.affiliation: Department of Psychology, University of Giessen, Otto-Behaghel-Straße 10F, 35394 Giessen, Germany; e-mail:  Christoph.Witzel@psychol.uni-giessen.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Witzel
authors.forename: Hanna
authors.initials: H
authors.lastname: Valkova
authors.forename: Thorsten
authors.initials: T
authors.lastname: Hansen
authors.forename: Karl R
authors.initials: KR
authors.lastname: Gegenfurtner
keywords: Artificial Objects; Colour Appearance; Colour Diagnosticity; Daylight Variation; Memory Colours; Object Colours; Past Experience; Prior Knowledge