European Conference on Visual Perception edition:32 location:Regensburg, Germany date:24-29 August 2009
Recent studies have found a larger neural activation for stimuli which are more extreme exemplars of their stimulus class, than for stimuli which are more prototypical. This has been shown for faces as well as familiar and novel object classes. We used a visual search task to look for a behavioral correlate of these findings regarding both simple geometrical shapes and novel object classes. The latter stimulus set enabled us to control for the physical properties of the objects, firmly establishing that the effects are solely due to the positions of the particular stimuli in the shape space of objects belonging to the same object class (ie, at the border vs more central). The results clearly indicate that finding an atypical instance of an object class amongst more typical ones is easier and faster than the other way around. These effects require several presentations of the object class, especially for the novel objects, which suggests that they are not due to short-term adaptation from individual stimuli in previous trials but are linked to habituation for the object class as a whole.In general, these findings point towards a mechanism that can be used to orient oneself towards objects that are somewhat unusual within the environment, ie with properties that are atypical for their object class.