Perceptual learning in human and nonhuman animals: A search for common ground

Abstract

Perceptual learning has been extensively studied in both human and nonhuman animals, but the two lines of research have, for the most part, developed independently, addressing seemingly rather different issues by rather different methods. It has been argued, however, that analysis of the disparate phenomena studied in experiments on perceptual learning reveals that in all the studies, the essential feature is that appropriate training allows behavior to come to be controlled by the unique features, rather than by the common features, of similar stimuli. It has further been argued that experiments with nonhuman animals have established the existence of a range of learning processes that allow this to occur, and that these processes have general relevance, applying to humans as well as to animals.

Varieties of perceptual learning

“…They have shown that if rats are exposed to AX and X in alternation and, in a separate block of trials, to CX, subsequent conditioning proceeds more rapidly to A than to C. Intermixed exposure to AX and X preserves the salience of A, whose representation is retrieved on the intervening X-alone trials, whereas no such effect is observed to C after a block of CX exposure trials. Other studies have revealed some problems for this interpretation Hall & Rodriguez, in press), and I think I can safely leave it to Hall's own contribution to this symposium (Hall, 2009) to make the case for his account. But, as was noted by Dwyer and Honey, most of these findings can probably also be derived from the McLaren and Mackintosh (2000) model.…”

Human and animal perceptual learning: Some common and some unique features

“…Mackintosh (2009) quotes Fahle's (2002, p. ix) definition, according to which perceptual learning "improves discrimination between stimuli that could not be discriminated before learning." Hall's (2009) definition of perceptual learning (originally stated in Hall, 2008) is very similar to Mackintosh's, but also hints at a mechanism by which improved discrimination might come about. Hall says that perceptual learning is "the learning process (or processes) that increases the effectiveness of the unique stimulus elements and/or reduces that of common stimulus elements, thus facilitating discrimination between similar stimuli" (p. 135).…”

“…The intermixed-blocked effect has received a great deal of attention recently because it cannot be explained in terms of the relative exposure to (and therefore familiarity of) the common and unique features; this is equivalent in the intermixed and blocked conditions. Nevertheless, three of the four theories that have been proposed to account for the intermixed-blocked effect (see Mackintosh, 2009)-and much of the data (e.g., Blair & Hall, 2003;Mitchell, Kadib, et al, 2008)-suggest that the unique features A and B are more salient following intermixed than following blocked preexposure (see Hall, 2009). …”

“…More generally, this theory suggests that, as two similar stimuli become more familiar, their unique features become relatively more salient. An increase in the salience of the unique features relative to the common features is all that is required to improve the discriminability of AX from BX (see also Hall, 2009). Mackintosh et al (1991) provided experimental confirmation that greater exposure to the common element than to the unique elements of two similar stimuli can produce a perceptual learning effect.…”

“…I shall briefly describe the associative approach to perceptual learning, as outlined in the articles by Hall (2009) and Mackintosh (2009), focusing on the finding that nonreinforced exposure to two similar stimuli can enhance their distinctiveness. The results described by Tsushima and Watanabe (2009) and some results from my own laboratory appear to be quite inconsistent with some aspects of the associative analysis.…”