Abstract
Longer adaptation durations usually induces stronger aftereffects. However, a recent study revealed that the strength of numerosity adaptation is primarily determined by the number of events an observer is exposed to rather than the duration of each exposure (Aagten-Murphy & Burr, 2016). We asked whether these dynamics also hold for classical aftereffects of tilt and motion, and for central vs. peripheral vision, which we found have very different adaptation dynamics (Gao et al. VSS 2018). Observers adapted to sequences of moving dots or tilted gabors and then nulled the motion or orientation bias each 2-sec for 120 post-adaptation trials. Adapt sequences varied in the number of discrete events (4 or 16) and their duration (0.25, 1, or 4 sec) and were presented in the fovea or 10–deg periphery. We averaged the first 10 or last 20 trials to estimate the peak aftereffect and residual (long-term) responses, respectively. Both were larger in the periphery for tilt but not motion. For tilt, the peak increased with both the number and duration of events, but for total equivalent durations, more frequent events induced larger aftereffects. The residual response increased with the number of adapting events but not with their duration. For motion, peak responses also increased with event number and duration, but more frequent events induced larger peak responses only in the periphery. Our results confirm the importance of adaptation frequency in addition to duration, but suggest the specific dynamics may depend on the stimulus, task, and retinal location.