Abstract
How the visual system encodes metric properties such as size and separation is still unclear. Regarding this, Hisakata, Nishida & Johnston (2016) reported a new adaptation effect in which the perceived separation of two dots or size of ring shrank after adaptation to a dense texture (density-size aftereffect). They proposed that the estimated separation (size) be coded relative to an adaptable spatial metric, which will be based on internal density representation. In many studies about visual adaptation, it is well known that the prolonged exposure to adaptation stimuli induces the larger aftereffect, whereas Aagten-Murphy & Burr (2016) reported that numerosity adaptation required a repetitive presentation, not long exposure of adaptation stimulus. According to a theory of magnitude (Walsh, 2003), the estimation of numerosity and size share a common metric, and it is likely that the density-size adaptation has the same temporal properties as the numerosity adaptation. Here, we investigated the time course of the density-size adaptation and the effects of both the frequency of the refresh of the adaptation stimulus and the adaptation duration. We used the staircase method to measure the time course. Adaptation had 60 trials. The adaptation duration in one trial was 1000ms or 5000ms and the total duration was 60s or 300s respectively. The position and polarity of the adaptation texture were refreshed every 100ms, 300ms, or 0ms (no-refresh). As the results, the perceived size after the 5000ms adaptation more shrank than 1000ms in all conditions. However, in the 5000ms adaptation condition, the refresh every 100ms and 300ms induced the greater aftereffects than the no-refresh situation, indicating that the repetitive presentation of adaptation texture enhanced the density-size aftereffect only when the adaptation duration was enough. We will discuss the relationship between a theory of magnitude and the density-size aftereffect from the temporal property of it.
Acknowledgement: KAKENHI Grant-in-Aid for Young Scientists 18K18341