Opposite effects of adaptation and priming: Speed discriminations during smooth pursuit G W Maus1, E Potapchuk1, S N Watamaniuk2, S J Heinen1 |
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1Smith-Kettlewell Eye Research Institute, CA, United States |
| Adaptation and priming have opposite effects. Adaptation to fast speeds lowers perceived speed; adaptation to slow speeds increases it. Conversely, priming from fast or slow pursuit causes higher or lower anticipatory smooth pursuit (ASP), respectively. Can these opposite effects occur simultaneously? Five observers performed perceptual speed discriminations while pursuing moving random dots, using the method of single stimuli. To assess the effect of adaptation on perception, we fit psychometric functions separately to responses binned according to average speed in the preceding 1-40 trials. Additionally, we analysed the residuals of binned responses from a fit to all data. Both analyses revealed perceptual adaptation: stimuli preceded by fast speeds were perceived as slower (and vice versa). To assess priming of ASP, we analysed eye velocity as a function of average stimulus speed in preceding trials, and found strong positive correlations. Interestingly, maximum ASP priming occurred for relatively short stimulus histories (~2 trials), whereas perceptual adaptation was maximal for much longer histories (~15 trials). Both effects could be the consequence of modifying an internal ‘standard’ speed representation that is used both for perceptual comparisons, and for generating anticipatory eye velocity. However, the temporal dissociation of the two effects suggests different underlying mechanisms. |
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