Familiar size effects on reaction time: When congruent is better.

Familiar size is known to influence our perception of object's size and distance. In this study, we examined whether or not simple RTs (RTs) are also affected by prior knowledge of objects' size. In a series of experiments, participants were asked to respond as quickly as possible to briefly presented images of familiar objects, equated for luminance and retinal size. The effects of familiar size and object animacy on RTs were investigated under natural (Experiment 1) and reduced (Experiment 2) viewing conditions. Restricted viewing conditions were introduced to manipulate the availability of depth cues. A systematic effect of familiar size on RTs was considered for progressively "shrunken" (Experiment 3) and "enlarged" (Experiment 4) objects on the screen with respect to their familiar size. Measures of perceived size were also taken by means of a manual estimation task (Experiment 5). Results showed an effect of animacy on simple RTs: Participants were faster to respond to images of animals than nonanimals. An effect of familiar size on simple RTs was also observed under reduced viewing conditions only: Objects shown closer to their real-world size were detected significantly more quickly than those further from their familiar size. However, this familiar-size advantage did not reflect perceived size. Hence, simple RTs under reduced viewing conditions are modulated by the degree of compatibility between physical size and long-term representations of size. (PsycINFO Database Record