Abstract
Participants usually respond faster to larger objects as compared to smaller objects. In order to perceive an object’s size, the brain needs to integrate contextual information such as object distance, an effect elucidated by various visual illusions. Accordingly, the perceived size of identical objects can differentially be altered via depth cues that create differentially perceived object distances. Recently, it has been demonstrated that simple reaction times are modulated by the perceived rather than by the retinal size of an object. This indicates that responses are generated subsequent to distance and retinal size integration. However, the timing aspects of these integration processes are largely unclear. Therefore, the present study investigated the influence of stimulus duration on size - distance integration by means of a simple reaction time paradigm. In two experiments we verified the effect that reaction times are susceptible to a variant of the well known Ponzo illusion. In the first experiment, participants reacted faster to perceptually longer lines in front of an illusion inducing background, whereas no such effect was associated with a neutral background. Subsequently, the second experiment revealed that this effect depends on stimulus duration time. Durations shorter than 40 ms did not elicit the reaction time effect. Hence, the present findings indicate that the visual system requires a minimum visual input in order to integrate context and object information. Before this minimum input is available the system seems to rely on lower visual representations.
Meeting abstract presented at VSS 2012