Labeling and family resemblance in the discrimination of polymorphous categories by pigeons (original) (raw)
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Journal of Experimental Psychology: Animal Behavior Processes, 2012
A model proposing error-driven learning of associations between representations of stimulus properties and responses can account for many findings in the literature on object categorization by nonhuman animals. Furthermore, the model generates predictions that have been confirmed in both pigeons and people, suggesting that these learning processes are widespread across distantly related species. The present work reports evidence of a category-overshadowing effect in pigeons' categorization of natural objects, a novel behavioral phenomenon predicted by the model. Object categorization learning was impaired when a second category of objects provided redundant information about correct responses. The same impairment was not observed when single objects provided redundant information, but the category to which they belonged was uninformative, suggesting that this effect is different from simple overshadowing, arising from competition among stimulus categories rather than individual stimuli during learning.
Journal of experimental psychology. Animal learning and cognition, 2018
Two experiments investigated what makes it more likely that pigeons' behavior will come under the control of multiple relevant visual stimulus dimensions. Experiment 1 investigated the effect of stimulus set structure, using a conditional discrimination between circles that differed in both hue and diameter. Two training conditions differed in whether hue and diameter were correlated in the same way within positive and negative stimulus sets as between sets. Transfer tests showed that all pigeons came under the control of both dimensions, regardless of stimulus set structure. Experiment 2 investigated the effect of the relative salience of the stimulus differences on three visual dimensions. Pigeons learned a multiple simultaneous discrimination between circular patches of sinusoidal gratings that differed in hue, orientation, and spatial frequency. In initial training, each stimulus only included one positive or negative feature, and the stimulus differences on the three dimens...
Categorical discrimination of objects and pictures by pigeons
Animal Learning & Behavior, 1992
With a three-choice instrumental discrimination procedure, pigeons were taught to distinguish small spherical objects from nonspherical objects. Spherical objects were defined as positive, nonspherical objects as negative. A device allowing an automatic presentation of the stimuli was employed. The subjects actually pecked the objects, and grain rewards were presented directly beside the correct objects. Acquisition was rapid, with the birds reaching a criterion of 80% correct choices within less than 150 trials. There was evidence that more than 200 objects were remembered individually over 3 months. Pigeons transferred the discrimination of sphericalJnonspherical objects to novel objects. The criteria by which the birds judged the sphericity of objects seemed to be similar to those applied by humans. They could apply the categorization in a relational manner and generalize it to apply to photographs and drawings of objects. The categorization competence was retained for at least 3 months.
Category discrimination by pigeons using five polymorphous features
Journal of the Experimental Analysis of Behavior, 1990
Eight pigeons were trained to discriminate between sets of color photographs of natural scenes. The scenes differed along five two-valued dimensions (site, weather, camera distance, camera orientation, and camera height), and all combinations of the feature values were used. One value of each dimension was designated as positive, and slid e feat lues were members Thus, each feature had an equal, low, correlation with reinforcement, and all features had zero correlations with each other. Seven of the 8 pigeons learned this discrimination, and their responding came under the control of all five features. Within the positive and negative stimulus sets, response rates were higher to stimuli that contained more positive feature values. Once discrimination had been achieved, reversal training was given using a subset of the slides. In this subset, only a single feature was correlated with reinforcement. All pigeons learned this reversal successfully and generalized it to additional photographs with the same feature content. After reversal, the original reinforcement contingencies were reinstated, and training was continued using all the slides except those that had been used in reversal. Reversal generalized to these slides to some extent. Analysis of the response rates to individual slides showed that, compared with prereversal training, only the feature that had been subjected to reversal contingencies showed a reversed correlation with response rate. The remaining features showed the same correlation with response rate as they had before reversal training. Thus, reversal on some members of a category following category discrimination training led to generalization to stimuli within the category that were not involved in the reversal, but not to features that were not reversed. It is therefore inappropriate to refer to the pgpons as earning a
Effects of stimulus manipulations on visual categorization in pigeons
Behavioural Processes, 2006
Four pigeons were previously trained . Pigeons concurrently categorize photographs at both basic and superordinate levels. Psychon. Bull. Rev. 11, 1111-1117 to classify color photographs into either their proper basic-level category (cars, chairs, flowers, or people) or a superordinate-level category (nominally natural or artificial). In Experiment 1, the same pigeons were shown either reflected or inverted versions of the training stimuli. Reflection had no effect on pigeons' classification behavior, whereas inversion impaired discrimination of all stimulus categories, except flowers, on the basic-level and superordinate-level tasks. Pixel matching analysis revealed that pattern matching played at most a minor role in the birds' categorization behavior. In Experiment 2, the pigeons were shown test stimuli that were either blurred or quartered and scrambled. Blurring impaired discrimination of cars, but had no effect on discrimination of people and flowers; scrambling impaired discrimination of people and flowers leaving discrimination of cars and chairs unaffected. These results suggest that categorization of flowers and people may be controlled primarily by the overall shape of the object rather than by local features, whereas categorization of cars and chairs may rely primarily on local features rather than the overall shape of the object.
Learning & Behavior, 2011
Pigeons were trained to classify composite faces of two categories created by mimicking the structure of basic-level categories, with each face consisting of an itemspecific component and a common component diagnostic for its category. Classification accuracy increased as the proportion of common components increased, regardless of familiar and novel item-specific components, with the best discrimination occurring at untrained original faces used as the common components. A no-categorization control condition suggested that categorization gives rise to equivalence for item-specific components and distinctiveness for degrees of prototypicality. When some item-specific components were shared by exemplars of the contrasting categories, those that were not overlapping between the categories became the effective cues for the pigeons' responses. Implications of these results are discussed in the context of current categorization and associative learning theories.
Pigeons concurrently categorize photographs at both basic and superordinate levels
Psychonomic Bulletin & Review, 2004
Categorizing environmental stimuli and generalizing these categories to novel instances are fundamental to many human cognitive activities. Some categories have a strict definition: A circle contains the set of all points that are equidistant from a reference point. But many categories do not have such clear-cut definitions. Instead of an object either belonging to a category or not, an object may differentially exemplify that category (E. E. Smith & Medin, 1981). Considerable research has been directed at understanding object categorization in humans (reviewed by Hampton, 2001; Mareschal & Quinn, 2001). Experimental Study of Object Categorization in Animals Object categorization has also been studied in nonhuman animals. Such studies typically involve animals' discrimination of photographs of objects from human language categories, using a variety of behavioral paradigms. In the first investigation of object categorization by birds, Herrnstein and Loveland (1964) trained pigeons to peck if a photograph contained a person and to refrain from pecking if a photograph did not contain a person. The pigeons readily learned the task and transferred the discrimination to novel photographs. Subsequent researchers have found that several animal species can acquire this presence/ absence discrimination involving pictures of people, trees,
Categorical learning in pigeons: the role of texture and shape in complex static stimuli
1999
Pigeons are known to be able to categorize a wide variety of visual stimulus classes. However, it remains unclear which are the characteristics of the perceptually relevant features employed to reach such good performance. Here, we investigate the relative contributions of texture and shape information to categorization decisions about complex natural classes.
Perceptual Differentiation During Categorization Learning by Pigeons
In Experiment 1, pigeons were trained to categorize two sets of variable stimuli (black and white checkerboard patterns), constructed by random distortions of two prototype patterns. They were subsequently trained on new discriminations, between two new exemplars of their positive category, two new exemplars of their negative category, or two control checkerboard patterns. The new exemplars of their familiar categories were easier to discriminate than the wholly novel stimuli, although this difference was significant only for exemplars of their previously negative category. In Experiment 2, pigeons were initially trained on a discrimination between two prototype checkerboards; they subsequently learned to discriminate between two distortions of their negative prototype more rapidly than between two control patterns.