Prototype effects in categorization by pigeons.

Abstract

In 4 experiments pigeons received a categorization task involving 6 simultaneous compounds in which the elements A, B, and C were more frequently paired with food than were the elements D, E, and F. Food was delivered after compounds ABF, AEC, and DEC but not after DEC, DBF, and AEF. Subsequent testing revealed a higher rate of responding during ABC than during any of the compounds that had signaled food and a lower rate of responding during DBF than during any of the compounds that had not signaled food. Experiments 2, 3, and 4 further demonstrated that the rate of responding during test trials with ABC was faster than during a compound composed of 3 elements that had individually been paired with food. The results are more consistent with a configural than an elemental analysis of discrimination and categorization. A frequent finding from studies of categorization with humans is that exemplars that can be said to represent the central tendency of a category are the easiest to classify correctly. Reed (1972) described one example of such a prototype effect; Reed showed students cartoon drawings of faces that belonged to two categories. The faces for one category had, on average, smaller foreheads, more closely spaced eyes, and shorter noses than those in the other category. Once the subjects were able to sort the faces correctly, test trials with novel patterns were given. The test patterns that were most accurately classified were those that corresponded to the averages of the faces belonging to the two categories, that is, the prototypes. In a rather different study, Posner and Keele (1968) generated four prototypical patterns from a number of dots. They then distorted these patterns to some extent by moving the dots, and the resultant figures were used for a catego-rization study. Once subjects were able to sort the distorted patterns into groups on the basis of their prototypes, they were required to sort a number of novel patterns, including the prototypes. The more similar a novel pattern was to a category prototype, the easier it was to classify. For the above-mentioned experiments, the prototypes were based on the mean values of the various dimensions from which the exemplars of the respective categories had been constructed. Prototype effects can also be observed when the test stimulus is based on a rather different measure of central tendency. Goldman and Homa (1977) conducted a study based on cartoon drawings of faces, in which the prototypical faces were composed of the features that most frequently appeared in the training faces. Such modal faces were classified more efficiently than any other faces, in

Categories as paradigms for comparative cognition

“…Such an effect is expressed by a better categorical performance with prototypical stimuli representing the central tendency of the categories than with other, less typical, exemplars. Thus, prototypical effects have been reported in studies with pigeons (von Fersen and Aydin and Pearce, 1994). However, in these studies the evidence of typicality effects is somewhat tempered by the previous associations between reinforcement and stimulus choice, given that the procedure involved the presentation of prototypical forms to subjects before testing.…”

Domestic pigeons (Columba livia) discriminate between photographs of male and female pigeons

“…1.0 Discrimination Ratio , , , NAKAMURA, ITO, CROFT, AND WESTBROOK 1983;von Fersen & Lea, 1990] and the prototype model [Aydin & Pearce, 1994;Huber & Lenz, 1996]) of categorical discrimination predict that pigeons' behavior would generalize to the stimuli not used in the partial reversal training (cf. Shettleworth, 1998).…”

Symmetry Preference as a Cognitive By-Product in Starlings

“…Some theories of feature learning propose that animals may learn the characteristics of a set of signals by generalizing the learned set to the arithmetic mean (e.g. Langlois & Roggman, 1990;Aydin & Pearce, 1994). In subsequent recognition tasks, animals (including humans) give strongest responses to stimuli that most closely resemble generalized averages (Kalish & Guttman, 1957;Blough, 1969;Strauss, 1979;Langlois & Roggman, 1990;Dill & Heisenberg, 1995;Enquist & Johnstone, 1997;Jansson et al, 2002).…”