The undesired selves of repressors

Previous research has shown that prototypes of familiar categories are preferred over novel exemplars of familiar and unfamiliar categories. The present research demonstrates a reversal of this effect by simply inducing an exploratory mindset. Specifically, participants were asked to judge the attractiveness of dot patterns that represented prototypes of familiar categories, exemplars of familiar categories, or exemplars of novel categories. An exploratory mindset was manipulated by asking participants to imagine the stimuli as stars (versus as peas). Results show that participants in the exploration condition preferred exemplars of novel categories (thereby reversing the classical prototypicality effect), whereas participants in the control condition preferred prototypes. The role of mindsets and familiarity in attractiveness ratings is discussed.     

Instance memorization and category influence: Challenging the evidence for multiple systems in category learning

A class of dual-system theories of categorization assumes a categorization system based on actively formed prototypes in addition to a separate instance memory system. It has been suggested that, because they have used poorly differentiated category structures (such as the influential “5-4” structure), studies supporting the alternative exemplar theory reveal little about the properties of the categorization system. Dual-system theories assume that the instance memory system only influences categorization behaviour via similarity to single isolated instances, without generalization across instances. However, we present the results of two experiments employing the 5-4 structure to argue against this. Experiment 1 contrasted learning in the standard 5-4 structure with learning in an even more poorly differentiated 5-4 structure. In Experiment 2, participants memorized the 5-4 structure based on a five minute simultaneous presentation of all nine category instances. Both experiments revealed category influences as reflected by differences in instance learnability and generalization, at variance with the dual-system prediction. These results have implications for the exemplars versus prototypes debate and the nature of human categorization mechanisms.     

The paradox of the universal triangle: Concepts,language, and prototypes

For over 300 years, the humble triangle has served as the paradigmatic example of the problem of abstraction. How can we have the idea of a general triangle even though every experience with triangles is with specific ones? Classical cognitive science seemed to provide an answer in symbolic representation. With its easily enumerated necessary and sufficient conditions, the triangle would appear to be an ideal candidate for being represented in a symbolic form. I show that it is not. Across a variety of tasks—drawing, speeded recognition, unspeeded visual judgments, and inference—representations of triangles appear to be graded and context dependent. I show that using the category name “triangle” activates a more prototypical representation than using an arguably coextensive cue, “three-sided polygon”. For example, when asked to draw “triangles” people draw more typical triangles than when asked to draw “three-sided polygons”. Altogether, the results support the view that (even formal) concepts have a graded and flexible structure, which takes on a more prototypical and stable form when activated by category labels.     

Category-contingent face adaptation for novel colour categories: Contingent effects are seen only after social or meaningful labelling

A face appears normal when it approximates the average of a population. Consequently, exposure to faces biases perceptions of subsequently viewed faces such that faces similar to those recently seen are perceived as more normal. Simultaneously inducing such aftereffects in opposite directions for two groups of faces indicates somewhat discrete representations for those groups. Here we examine how labelling influences the perception of category in faces differing in colour. We show category-contingent aftereffects following exposure to faces differing in eye spacing (wide versus narrow) for blue versus red faces when such groups are consistently labelled with socially meaningful labels (Extravert versus Introvert; Soldier versus Builder). Category-contingent aftereffects were not seen using identical methodology when labels were not meaningful or were absent. These data suggest that human representations of faces can be rapidly tuned to code for meaningful social categories and that such tuning requires both a label and an associated visual difference. Results highlight the flexibility of the cognitive visual system to discriminate categories even in adulthood.     

Category contingent aftereffects for faces of different races, ages and species

Exposure to faces biases perceptions of subsequently viewed faces such that normality judgments of similar faces are increased. Simultaneously inducing such an aftereffect in opposite directions for two groups of faces might indicate discrete responding of the neural populations coding for those groups. Here we show such "category contingent" aftereffects following exposure to faces differing in eye-spacing (wide versus narrow) for European versus African faces, adult versus infant faces, and human versus monkey faces. As aftereffects reflect changes in responses of neural populations that code faces, our results may then suggest that functionally distinct neural populations code faces of different ages, races and species and that the human brain potentially contains discrete representations of these categories.     

Categorization generated by extended prototypes—An axiomatic approach

We suggest a model of categorization based on prototypes. A set of entities, identified with some finite dimensional Euclidian space, is partitioned into a finite number of categories. Such a categorization is said to be generated by extended prototypes if there is a set of distinguished entities, one for each category, such that the categorization is determined by proximity to these prototypical entities. The prototypes are called extended since they are described by points in a higher dimensional space than the entities. Sufficient conditions for a categorization to be generated by extended prototypes are provided. These conditions are also necessary if the prototypes are in general position.     

How status and stereotypes impact attributions to discrimination: The stereotype-asymmetry hypothesis

Past research suggests a status-asymmetry effect in attributions to discrimination such that people are more likely to make attributions to discrimination when the victim is from a lower status group than the perpetrator as compared to when the victim is from a higher status group than the perpetrator. The present studies test a stereotype-asymmetry effect, such that people are more likely to make attributions to discrimination when rejection occurs in a domain in which the victim is negatively rather than positively stereotyped. In Study 1 (observers) and Study 2 (victims), participants attributed rejection following a job interview to discrimination more when the victim was negatively stereotyped than when the victim was positively stereotyped. The stereotypicality of the domain was more important than the relative status of the victim and the perpetrator in determining judgments of discrimination. Thus stereotype-asymmetry is a key feature of the discrimination prototype.     

Refining the visual-cortical hypothesis in category learning

Participants produce steep typicality gradients and large prototype-enhancement effects in dot-distortion category tasks, showing that in these tasks to-be-categorized items are compared to a prototypical representation that is the central tendency of the participant’s exemplar experience. These prototype-abstraction processes have been ascribed to low-level mechanisms in primary visual cortex. Here we asked whether higher-level mechanisms in visual cortex can also sometimes support prototype abstraction. To do so, we compared dot-distortion performance when the stimuli were size constant (allowing some low-level repetition-familiarity to develop for similar shapes) or size variable (defeating repetition-familiarity effects). If prototype formation is only mediated by low-level mechanisms, stimulus-size variability should lessen prototype effects and flatten typicality gradients. Yet prototype effects and typicality gradients were the same under both conditions, whether participants learned the categories explicitly or implicitly and whether they received trial-by-trial reinforcement during transfer tests. These results broaden out the visual-cortical hypothesis because low-level visual areas, featuring retinotopic perceptual representations, would not support robust category learning or prototype-enhancement effects in an environment of pronounced variability in stimulus size. Therefore, higher-level cortical mechanisms evidently can also support prototype formation during categorization.     

Typicality, graded membership, and vagueness

This paper addresses theoretical problems arising from the vagueness of language terms, and intuitions of the vagueness of the concepts to which they refer. It is argued that the central intuitions of prototype theory are sufficient to account for both typicality phenomena and psychological intuitions about degrees of membership in vaguely defined classes. The first section explains the importance of the relation between degrees of membership and typicality (or goodness of example) in conceptual categorization. The second and third section address arguments advanced by Osherson and Smith (1997), and Kamp and Partee (1995), that the two notions of degree of membership and typicality must relate to fundamentally different aspects of conceptual representations. A version of prototype theory-the Threshold Model-is proposed to counter these arguments and three possible solutions to the problems of logical selfcontradiction and tautology for vague categorizations are outlined. In the final section graded membership is related to the social construction of conceptual boundaries maintained through language use.