A Brief Motion Adaption Changes Subjective Time of Dynamic Visual Events
Doğa Gülhan & İnci Ayhan
- Humans process temporal information over a large scale ranging from microseconds to daily circadian rhythms. Memory does not intervene with the evaluation of brief durations in the sub-second range; thus, time judgments within this range are automatic, parallel and perceptual, rather than under cognitive control. Here, using psychophysical methodologies, we show - for the first time - a novel adaptation effect, where a dynamic short-term (700 ms) adaptor induces a significant subjective duration compression (~10%) on a subsequently presented test stimulus only for dot arrays with 50% of dots moving at a coherent motion direction but not for those with individual dots drifting at random directions, showing that the effect is tuned to sensory motion signals processed by the higher-level global motion areas such as area MT+. In another experiment using a two-dimensional pattern motion stimulus called as plaid as adaptor and its component gratings as tests, we report a significant duration compression selective to the relative direction of the standard test to that of the plaid’s global pattern, implying a high-level direction selectivity. Further experiments provide evidence that this subjective time compression is dissociated from adaptation-induced changes in perceived speed and that is present even under interocular conditions, where the adaptor is presented monocularly onto one eye, and the test stimulus onto the other, which together imply explicit genuine mechanisms mediating duration effects in higher-level motion areas. These results are discussed within the context of increasing evidence for a hypothetical sensory duration pathway starting from the early-level regions towards the higher level areas in the visual brain.
- Demo (2.5 deg/sec, 50% coherence)
