NOT THERE, WHERE IS IT - LOCATING ILLUSORY CONJUNCTIONS

There is evidence that complex objects are decomposed by the visual sy stem into features, such as shape and color. Consistent with this theo ry is the phenomenon of illusory conjunctions, which occur when featur es are incorrectly combined to form an illusory object. We analyzed th e perceived location of illusory conjunctions to study the roles of co lor and shape in the location of visual objects. In Experiments 1 and 2, participants located illusory conjunctions about halfway between th e veridical locations of the component features. Experiment 3 showed t hat the distribution of perceived locations was not the mixture of two distributions centered at the 2 feature locations. Experiment 4 repli cated these results with an identification task rather than a detectio n task. We concluded that the locations of illusory conjunctions were not arbitrary but were determined by both constituent shape and color.