Perceptual learning: Functions, mechanisms, and applications

The first International Workshop on Perceptual Learning was held at Beijing Normal University in Beijing, China, from October 15, 2008 to October 19, 2008. The workshop brought together more than 20 world-class investigators frommany complementary disciplines – psychophysics, neurophysiology, functional imaging, computational neuroscience, and perceptual rehabilitation, all contributors to the study of the functions, mechanisms, and applications of perceptual learning. Participants of the workshop not only reported the latest advances in their research, but also engaged in lively discussions and friendly debates both in the scheduled discussion period after each talk and during many social events. We all agreed that the first workshop was extremely successful in fostering exchanges of ideas and multidisciplinary collaborations. Following the workshop, we invited all the participants and many other investigators on perceptual learning who could not attend the workshop for various reasons to contribute to a Special Issue of Vision Research on perceptual learning. We received about two-dozen submissions. Because of the large number of manuscripts, the special issue is published in two volumes. The first volume was published in Volume 49, Number 21 of Vision Research in October, 2009 (Lu, Yu, Watanabe, Sagi, & Levi, 2009). The current issue is the second volume of the Vision Research Special Issue on Perceptual Learning. It consists of the second half of the accepted manuscripts from the submission pool. In the first paper, Zhang, Xiao, Klein, Levi, and Yu (2010) reexamined the location specificity of practice effects in orientation discrimination. Surprisingly, they find that the learning effect is transferred to an untrained location if the latter is exposed to a short pre-test before practice. It becomes clear that perceptual learning is not a single process but rather a process involving different levels of processing operating on different scales in space and time (Ahissar & Hochstein, 2004; Karni & Sagi, 1993) with bi-directional transfer of learning (Censor & Sagi, 2009, in the first special issue). Most importantly, this study adds to the accumulating results showing that details of the training schedule thought to be irrelevant for transfer affect specificity of learning, including task precision (Jeter, Dosher, Petrov, & Lu, 2009), task difficulty (Ahissar & Hochstein, 1997), and number of trials (Censor & Sagi, 2009). Lu, Liu, and Dosher (2010) tested the Augmented Hebbian Reweighting Model (AHRM) developed by Petrov, Dosher, and Lu (2005) against empirical results on mechanisms of perceptual learning by applying the AHRM to data from experiments in which external noise was explicitly manipulated. In this elegant model, perceptual learning strengthens or maintains the connections be-