Categorical discrimination and generalization in pigeons: All negative stimuli are not created equal.

Abstract

Three experiments investigated categorical discrimination and generalization in pigeons. Multiple fixed interval-extinction training was conducted with a pool of 48 different negative discriminative stimuli (12 slides each of people, flowers, cars, and chairs). The most errors were committed to negative stimuli (S-s) from the same category as the 12 positive stimulus (S+) slides. Such categorical generalization was stronger when the 12 S+s entailed 1 copy of 12 different slides (Experiment 2) than when the S+s entailed 12 copies of 1 slide (Experiment 1). In addition, reliable but incomplete loss of inhibitory control was observed to novel stimuli chosen from the same category as the S-slides (Experiment 3). These results are consistent with perceptual theories of categorical coherence, according to which preexisting similarities among stimuli chiefly determine the acquisition and application of categories.We thank Don Dorfman,

Concept Learning in Animals

“…This generalization decrement can be explained by a host of different theories of conceptual behavior --from exemplar models to prototype models (Smith & Medin, 1981; also see Astley & Wasserman, 1992). This behavioral fact suggests that the pigeons had memorized some or all of the photographic stimuli that they had seen during training, although nothing in the training regimen required them to do so.…”

“…A final experiment (Astley & Wasserman, 1992; Experiment 2), provides perhaps the most direct evidence on the perceived similarity of category members. There, pigeons learned a successive go/no go discrimination with 60 slides: 12 S+ stimuli and 48 S-stimuli.…”

Discrimination of individual vocalizations by black-capped chickadees (Poecile atricapilla)

“…We adapted our reversal method from the discrimination reversal procedure used by Astley and Wasserman (1992) to test for the transfer of category learning in pigeons. In the discrimination reversal procedure, novel test stimuli (from the same categories as the training stimuli) are substituted for the training stimuli.…”

Using the reassignment procedure to test object representation in pigeons and people

“…Thus, species as distinct from one another as humans, baboons, and pigeons may be using similar underlying object representations, although the extent to which these representations might be flexibly used across diverse tasks might differ. Astley and Wasserman (1992) used a go/no-go paradigm to see if untrained stimulus similarities, such as those between different views of the same object or between different members of the same category, might be spontaneously exhibited. The results of Astley and Wasserman as well as those of Peissig et al (2000b) support theories of categorical coherence, which propose that perceptual similarity plays a key role in the formation of categories.…”

“…Wasserman and colleagues tested for category formation using a wide variety of procedures (Astley, Peissig, & Wasserman, 2002;Astley & Wasserman, 1992, 1998, 1999Bhatt & Wasserman, 1989;Wasserman & Bhatt, 1992); the reassignment procedure was the only one to fail (Bhatt & Wasserman, 1989). In the hope of providing a more sensitive assessment of the reassignment method in the present study, we deployed it in a setting that involves a particularly basic form of categorization: generalizing across large changes (e.g., ≤ 72°of depth rotation) in views of the same object, where the competing stimuli were different objects, varying in non-accidental properties (NAPs; Biederman, 1987).…”