Temporal enhancement of cross-adaptation between density and size perception based on the theory of magnitude

The estimation of spatial distances is one of the most important perceptual outputs of vision and can easily be deduced even with detached objects. However, how the visual system encodes distances between objects and object sizes is unclear. Hisakata, Nishida, and Johnston (2016) reported a new adaptation effect, in which the perceived distance between objects and the size of an object shrink after adaptation to a dense texture. They proposed that the internal representation of density plays a role in a spatial metric system that measures distance and size. According to the theory of magnitude (Walsh, 2003), the estimation of spatial extent (distance and size) shares common metrics with the estimation of temporal length and numerosity magnitudes and is processed at the same stage. Here, we show the existence of temporal enhancement in cross-adaptation between density and size perception. We used the staircase method to measure the temporal property. The test stimuli were two circles, and the adapting stimulus had a dotted texture. The adapting texture refreshed every 100 or 300 ms, or not at all (static), during the adaptation. The results showed that the aftereffects from a refreshing stimulus were larger than those under the static condition. On the other hand, density adaptation lacked such enhancement. This result indicates that repetitive presentation of an adapting texture enhanced the density-size cross-aftereffect. According to the theory of magnitude, a common mechanism encodes spatial and temporal magnitude estimation and the adaptation to temporal density explains this cross-adaptation enhancement.