Can theories of animal discrimination explain perceptual learning in humans?

Abstract

We present a review of recent studies of perceptual learning conducted with nonhuman animals. The focus of this research has been to elucidate the mechanisms by which mere exposure to a pair of similar stimuli can increase the ease with which those stimuli are discriminated. These studies establish an important role for 2 mechanisms, one involving inhibitory associations between the unique features of the stimuli, the other involving a long-term habituation process that enhances the relative salience of these features. We then examine recent work investigating equivalent perceptual learning procedures with human participants. Our aim is to determine the extent to which the phenomena exhibited by people are susceptible to explanation in terms of the mechanisms revealed by the animal studies. Although we find no evidence that associative inhibition contributes to the perceptual learning effect in humans, initial detection of unique features (those that allow discrimination between 2 similar stimuli) appears to depend on an habituation process. Once the unique features have been detected, a tendency to attend to those features and to learn about their properties enhances subsequent discrimination. We conclude that the effects obtained with humans engage mechanisms additional to those seen in animals but argue that, for the most part, these have their basis in learning processes that are common to animals and people. In a final section, we discuss some implications of this analysis of perceptual learning for other aspects of experimental psychology and consider some potential applications.

Analysis of the role of stimulus comparison in discrimination learning in Pigeons

“…The results reported here accord with the conclusion of Mitchell and Hall (2014) that although the opportunity for comparison facilitates perceptual learning in studies with human participants, it does not do so for animal subjects. As we have noted, animals given exposure in which the stimuli are presented concurrently can sometimes show retarded acquisition of a subsequent discrimination between them (Alonso & Hall, 1999;Rodriguez et al, 2008).…”

“…In these experiments the interval between preexposure trials was long and reducing it, a procedure that might be expected to facilitate comparison, has uniformly been found to convey no special advantage (and sometimes to be disadvantageous) (e.g., Alonso & Hall, 1999;Bennett & Mackintosh, 1999;Rodriguez, Blair, & Hall, 2008). In a recent review, Mitchell and Hall (2014) concluded that a difference in the ability to benefit from the opportunity to compare the stimuli might constitute an important distinction between the perceptual learning effects seen in animals and those seen in humans.…”

Within-subjects assessment of the within-compound associations resulting from intermixed and blocked preexposure schedules

“…In these experiments, it is unlikely that the participants would have detected the unique stimulus features from the beginning of preexposure, which would make the formation and strengthening of any within-compound associations involving those features difficult. Under these circumstances, it seems more probable that the intermixed-blocked effect would have been generated by the ability of the intermixed schedule to enhance the salience of (and thus the detection of) the unique stimulus features (Mitchell & Hall, 2014). It remains, however, to specify the role played by the within-compound associations in producing this enhancement of salience.…”

“…However, the nature of the learning mechanism, or mechanisms, responsible for these changes in discriminability is currently a matter of theoretical debate (for a recent review, see Mitchell & Hall, 2014). One of the most accepted explanations for the effect is in terms of changes in the salience of the stimulus features.…”

Perceptual learning transfer: Salience of the common element as a factor contributing to the intermixed/blocked effect.

“…However, in the case of the unique features, by virtue of their associative activation (A and B would be activated in the BX and AX trials respectively, resulting in internal input but not external input), the salience/associability would be preserved (as predicted by, e.g., Hall et al, 2006;Mitchell & Hall, 2014). That would account for the high salience of A and B typically observed after intermixed preexposure (e.g., Artigas, Sansa, Blair, Hall, & Pra dos, 2006;Blair & Hall, 2003).…”