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RDATE:20371101T010000 TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:America/New_York EDT END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT UID:dcc386d4461a42d29a6d3c5e49ec9259 CATEGORIES:Human and computer vision series:Fall 2014 CREATED:20151203T141544 SUMMARY:Studying color constancy using natural tasks LOCATION:Post-doctoral Fellow\, University of Pennsylvania\, Department of Psycholog y DESCRIPTION:
In everyday life we rely on color information to select objects as the t argets of our actions (e.g., the ripest fruit, the freshest fish). To be us eful for such tasks, our perception of object color needs to correspond to object surface reflectance across a wide range of contexts in which the obj ect is viewed. It is well known that the visual system partially compensate s for the variable effects of context (such as changes in illumination) to maintain certain degree of stability of object color appearance, but whethe r this color constancy supports accurate object selection is not understood .
To study how color constancy guides real-life object se lection we developed a paradigm in which we asked subjects to select object s based on color across an illumination change. In a basic color selection task, the subjects selected which of the two test objects presented under o ne illumination appeared closer in color to the target object presented und er a different illumination. From subjects’ choices, we inferred a cr oss-illumination selection-based match for the target via a variant of the maximum likelihood difference scaling method, and used the inferred match t o quantify constancy. Our results show that selection-based constancy is go od when measured using naturalistic stimuli, but is dramatically reduced wh en the stimuli are simplified, indicating that a certain degree of stimulus naturalness is critical for good constancy.
We used our basic color- selection task as a building block in the development of more complex goal- directed tasks for which color is instrumental. In a blocks-copying task, f or example, we asked subjects to recreate an arrangement of colored blocks across a change in illumination. Our results show that color constancy mech anisms support accurate cross-illumination object selection in this task. p>
Our current studies aim to extend our understanding of how constancy o perates in real-life tasks by probing how variations in stimulus context mo dulate selection-based constancy and whether naturalistic appearance-based feedback can affect subjects’ performance.
CONTACT:Dr. Ana Radonjic X-EXTRAINFO:Dr. Ana Radonjic (http://www.sas.upenn.edu/~radonjic/) DTSTAMP:20240329T022900 DTSTART;TZID=America/New_York:20141103T120000 DTEND;TZID=America/New_York:20141103T190000 SEQUENCE:0 TRANSP:OPAQUE END:VEVENT END:VCALENDAR