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Hongjing Lu, Zili Liu; Perceptual learning of speed discrimination enhances motion after effect (MAE). Journal of Vision 2004;4(8):289. doi: 10.1167/4.8.289.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: to study the effect of motion perceptual learning on the strength of MAE; and to test whether perceptual learning of speed discrimination will make speed estimation more reliable, or the perceived speed interval larger, or both. Method: 1) Each of two radially inward random-dots motions (1.44 deg/s & 1.62 deg/s in speed) was psychometrically estimated against outward motion stimuli, in a 2AFC “which is faster?” 2) MAE was psychometrically measured for outward and inward motions, respectively, as follows. After adapting for 15s to a stimulus (55 dots/deg2, 1000 dots total) with a speed of 1.44 deg/sec, subjects decided if a test stimulus moved inward or outward with the method of random dynamic visual noise (Hiris & Blake 1992). 3) Subjects discriminated for eight daily sessions, 400 trials each, which of two inward motions in a trial (1.44 deg/s vs. 1.62 deg/s) was faster, with feedback. 4) Repeat of 2). 5) Repeat of 1). Results: Five subjects improved significantly in speed discrimination. All showed stronger MAE for the inward (trained) adapting motion. For the outward motion control, their MAE was either reduced or little changed. The psychometric curve for each of the two inward speeds became steeper after learning, indicating that these two speeds are now perceived with less variance. We found no evidence however that these two speeds were now perceived as being slower as a result of perceptual learning. Neither did we find that the perceived difference between these two speeds was enlarged. Discussion: Clifford & Wenderoth (1999) have found that motion adaptation improves speed discrimination at the expense of a slower estimation of absolute speed. Here, we found that perceptual learning also improves speed discrimination but without this expense. We also found that this perceptual learning enhances MAE. We suggest that perceptual learning may be viewed as a longer-term adaptation (Teich & Qian 2003).
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