Basic objects in natural categories

Categorizations which humans make of the concrete world are not arbitrary but highly determined. In taxonomies of concrete objects, there is one level of abstraction at which the most basic category cuts are made. Basic categories are those which carry the most information, possess the highest category cue validity, and are, thus, the most differentiated from one another. The four experiments of Part I define basic objects by demonstrating that in taxonomies of common concrete nouns in English based on class inclusion, basic objects are the most inclusive categories whose members: (a) possess significant numbers of attributes in common, (b) have motor programs which are similar to one another, (c) have similar shapes, and (d) can be identified from averaged shapes of members of the class. The eight experiments of Part II explore implications of the structure of categories. Basic objects are shown to be the most inclusive categories for which a concrete image of the category as a whole can be formed, to be the first categorizations made during perception of the environment, to be the earliest categories sorted and earliest named by children, and to be the categories most codable, most coded, and most necessary in language.     

Knowledge-based classification of ill-defined categories

In this paper, I report an exploratory study which investigated the role that prior knowledge plays in influencing classification learning. Under neutral or knowledge-imposing instructions, subjects learned to classify exemplars into categories that either were or were not linearly separable. Linearly separable categories are those categories whose members can be correctly classified based on an additive summation of weighted attribute information. Following category learning, the subjects were given transfer tests. A major finding was that knowledge facilitated the learning of linearly separable categories but interfered with the learning of not linearly separable categories. Quantitative analyses revealed that the knowledge facilitated category learning of the linearly separable categories by influencing the storage and reliance on both prototypical and exemplar information.     

On domain differences in categorization and context variety

Membership in many natural categories is considered all-or-none, while membership in most artifact categories is found to be graded. We introduce an alternative for the prevailing view that this domain difference in categorization results from representational differences. The context variety account posits that an item’s gradedness reflects the variety of contexts it appears in. Items that feature in a variety of contexts are assumed to be more likely to elicit a graded categorization response, since the suggested target category only provides one of many solutions to the question of the item’s identity. We review earlier work that suggested a domain difference in context variety, with artifactual items appearing in a greater variety of contexts than natural ones. The context variety domain difference is established in two separate experiments but is shown not to explain the domain difference in categorization. A selection of artifactual and natural items, for which the domain difference in context variety is reversed, is presented for categorization in a third experiment. This selection, too, fails to provide evidence for the context variety account of categorization differences. The domain difference in categorization is shown to be robust against this manipulation. Context variety appears to have no bearing on categorization, so the context variety account is not a sustainable alternative to accounts that posit representational differences between natural and artifact categories.     

The effect of context on the structure of categories

Three experiments examined the effect of context on the representativeness ordering of exemplars of a category. Experiments 1 and 2 employed an online reading time paradigm to examine the effect of context on the time it takes to establish an anaphoric reference between an exemplar and a category term. Experiment 1 demonstrated that context can change the relation between a category term and an exemplar at the time of comprehension. Experiment 2 showed that category terms presented in context generate graded goodness-of-example distributions of exemplars that are different from the distributions generated in the absence of explicit context. These distributions cannot be derived by assuming that the exemplar most strongly suggested by the context serves as the category representation. Experiment 3 employed a membership verification paradigm. Response time was found to be a function of degree of relatedness to the contextdependent category representation. Typicality, as determined in the absence of explicit context, had no effect on decision time. Several models, including some extensions of current semantic memory theories, are developed to account for the results of these experiments.     

Influences of culture and visual context on real-time social categorization

Social categorization is often thought to be based on facial features and immune to visual context. Moreover, East Asians have been argued to attend to context more than Westerners. American and Chinese participants were presented with faces varying along a White-Asian morph continuum either in American, neutral, or Chinese contexts. American contexts made White categorizations more likely, and Chinese contexts made Asian categorizations more likely. Further, the compatibility between facial and contextual cues influenced the directness of participants' hand trajectories en route to selecting a category response. Even when an ultimate response was not biased by context, the trajectory was nevertheless partially attracted to the category response associated with the context. Importantly, such partial attraction effects in hand trajectories revealed that the influence of context began earlier in time for Chinese relative to American participants. Together, the results show that context systematically influences social categorization, sometimes altering categorization responses and other times only temporarily altering the process. Further, the timing of contextual influences differs by culture. The findings highlight the role of contextual and cultural factors in social categorization.     

The base-rate fallacy in the context of sequential categories

Three experiments assessed base-rate utilization in a paradigm in which the relevant categories of the population were trials in sequences of variable length. In one version of stimulus materials, for example, a trial was represented by a toss of a coin, and a sequence was a series of coin tosses. Since each described sequence was to end upon the scoring of a “hit” in any trial, the likelihood of a trial’s being attempted was a decreasing function of its position in the sequence. Subjects who estimated the particular trial upon which the hit in a sequence was most likely to occur showed a significant tendency to ignore the probable higher prevalence—the greater base rate— of early trials in the overall population of atttempts, typically estimating that the hit in the sequence was equally likely on any trial. This tendency, however, was modified by the specific problem context. In all experiments, significantly more normatively correct estimates were made in the coin context, in which the disparity between base rates of early trials and later trials was most pronounced. Although subjects in the third experiment who had previously taken a statistics course displayed superior performance on the coin problem, there was no evidence of transfer of this superiority to another context. These results are interpreted within the theoretical framework of the base-rate fallacy. In particular, the article discusses implications of the finding that general base rates may be ignored even in the absence of specific diagnostic indicators.     

A demonstration of intransitivity in natural categories

Two experiment are reported which demonstrated intransitivity in category judgments, thus challenging a widely held assumption that the relation between categorized sets is one of class inclusion. Subjects consistently accepted the truth of certain category statements, in spite of being aware of the existence of counterexamples. Implications for semantic memory theory are discussed.     

A note on natural numbers objects in monoidal categories

The internal language of a monoidal category yields simple proofs of results about a natural numbers object therein.     

Necessity and natural categories.

Our knowledge of natural categories includes beliefs not only about what is true of them but also about what would be true if the categories had properties other than (or in addition to) their actual ones. Evidence about these beliefs comes from three lines of research: experiments on category-based induction, on hypothetical transformations of category members, and on definitions of kind terms. The 1st part of this article examines results and theories arising from each of these research streams. The 2nd part considers possible unified theories for this domain, including theories based on ideals and norms. It also contrasts 2 broad frameworks for modal category information: one focusing on beliefs about intrinsic or essential properties, the other focusing on interacting causal relations.     

Monoidal categories with natural numbers object

The notion of a natural numbers object in a monoidal category is defined and it is shown that the theory of primitive recursive functions can be developed. This is done by considering the category of cocommutative comonoids which is cartesian, and where the theory of natural numbers objects is well developed. A number of examples illustrate the usefulness of the concept.This work was partially carried out while both authors were guests of McGill University and while the second author was a guest of Dalhousie University. Both authors acknowledge support from the Natural Sciences and Engineering Research Council of Canada and the Québec Department of Education.     

Uncertainty orientation in the group context: categorization effects on persuasive message processing

Persuasive messages often originate from in-group or out-group sources. Theoretically, in-group categories could facilitate heuristic-based message processing (because of the attractiveness of in-groups and their social reality cues) or systematic-based processing (because of high personal relevance of the message). The authors expected individual differences in uncertainty orientation and socially based expectancy congruence to be important variables in understanding these processes. Participants were exposed to strong or weak, in-group or out-group messages that were either expectancy congruent (in-group agreement, out-group disagreement) or expectancy incongruent (in-group disagreement, out-group agreement). As predicted, uncertainty-oriented participants increased systematic information processing under incongruent conditions relative to congruent (i.e., relatively certain) conditions; certainty-oriented individuals processed systematically only under congruent conditions. These findings suggest that uncertainty that has been created through social-categorization conflicts is treated differently by people of different personality styles.     

Visual classes and natural categories in the pigeon

After being trained on an oak leaf pattern, pigeons responded to other oak leaf patterns but not to leaf patterns of other species. Thus, graphic variation among the instances of a species is "transparent" to the visual system. At this taxonomic level, concept formation is spontaneous rather than inductive. It is argued that such immediate generalization may be critical to the survival of the organism.     

Inference and classification learning of abstract coherent categories

Category learning research has primarily focused on how people learn to classify items using simple observable features. However, classification is only 1 way to learn categories. In addition, many concepts have an underlying coherence that explains the featural similarity among exemplars, such as abstract coherent concepts whose instances differ greatly on their observable features. In 3 experiments, the authors investigated how abstract coherent categories are acquired through 2 common means of category learning, classification and inference. Because inference promotes more focus on within-category information than does classification, they hypothesized that inference learning would lead to a better understanding of the underlying coherence of abstract coherent categories. All 3 experiments support this prediction.     

Visual categorization of natural stimuli by domestic dogs

One of the fundamental issues in the study of animal cognition concerns categorization. Although domestic dogs (Canis familiaris) are on the brink to become one of the model animals in animal psychology, their categorization abilities are unknown. This is probably largely due to the absence of an adequate method for testing dogs’ ability to discriminate between large sets of pictures in the absence of human cueing. Here we present a computer-automated touch-screen testing procedure, which enabled us to test visual discrimination in dogs while social cueing was ruled out. Using a simultaneous discrimination procedure, we first trained dogs (N = 4) to differentiate between a set of dog pictures (N = 40) and an equally large set of landscape pictures. All subjects learned to discriminate between the two sets and showed successful transfer to novel pictures. Interestingly, presentation of pictures providing contradictive information (novel dog pictures mounted on familiar landscape pictures) did not disrupt performance, which suggests that the dogs made use of a category-based response rule with classification being coupled to category-relevant features (of the dog) rather than to item-specific features (of the background). We conclude that dogs are able to classify photographs of natural stimuli by means of a perceptual response rule using a newly established touch-screen procedure. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Articulation in the context of edge classification

Many researchers believe the human visual system classifies luminance edges into those produced by reflectance edges or those produced by illumination edges, yet this classification process is not completely understood. One suggestion is that heuristics are used for edge classification. For example. specific contrast relationships at the luminance edge ('codirectional contrast invariance' and 'transversal luminance-ratio preserving') may distinguish an illumination edge from a reflectance edge on the one hand, and from a translucent edge on the other. Distinct from luminance junctions, these features are global characteristics of the luminance pattern that make distinguishing between different types of edge easier with more highly articulated scenes. I demonstrate that apparent translucency, nonreversing X-junctions, and single-reversing X-junctions are insufficient on their own to produce the lightness illusion of Adelson's well-known tile pattern. While tolerating violations of the codirectional contrast invariance and transversal-luminance-ratio presersving without reversing the sign of contrast, the visual system is quite sensitive to such contrast reversal at the luminance edge. I account for this by suggesting that humans process lightness in terms of an ordinal, rather than interval, (or ratio) scale.     

Motivated social categorization: fundamental motives enhance people's sensitivity to basic social categories

This article presents an evolutionary framework for identifying the characteristics people use to categorize members of their social world. Findings suggest that fundamental social motives lead people to implicitly categorize social targets based on whether those targets display goal-relevant phenotypic traits. A mate-search prime caused participants to categorize opposite-sex targets (but not same-sex targets) based on their level of physical attractiveness (Experiment 1). A mate-guarding prime interacted with relationship investment, causing participants to categorize same-sex targets (but not opposite-sex targets) based on their physical attractiveness (Experiment 2). A self-protection prime interacted with chronic beliefs about danger, increasing participants' tendency to categorize targets based on their racial group membership (Black or White; Experiment 3). This work demonstrates that people categorize others based on whether they display goal-relevant characteristics reflecting high levels of perceived desirability or threat. Social categorization is guided by fundamental evolved motives designed to enhance adaptive social outcomes.     

The spouse subsystem in the family context: couple interaction categories

Within a semi-structured family interview (the McMaster Stuctured Interview of Family Functioning), several questions focus on intimate areas of the marital relationship. How couples answer these questions provides a window into their style of communication around potentially stressful issues. Viewing their videotaped interactions while noting their gaze patterns, dialogue, tension, and attitude, produced the following categories: Adaptive, Stable, Co-operative, Disengaged/anxious, Parallel, or Failing. Inter-observer relability was high, and the categories were related in meaningful ways to a self-report questionnaire, the McMaster Family Assessment Device, completed independently by each parent.     

Visual context modulates potentiation of grasp types during semantic object categorization

Substantial evidence suggests that conceptual processing of manipulable objects is associated with potentiation of action. Such data have been viewed as evidence that objects are recognized via access to action features. Many objects, however, are associated with multiple actions. For example, a kitchen timer may be clenched with a power grip to move it but pinched with a precision grip to use it. The present study tested the hypothesis that action evocation during conceptual object processing is responsive to the visual scene in which objects are presented. Twenty-five healthy adults were asked to categorize object pictures presented in different naturalistic visual contexts that evoke either move- or use-related actions. Categorization judgments (natural vs. artifact) were performed by executing a move- or use-related action (clench vs. pinch) on a response device, and response times were assessed as a function of contextual congruence. Although the actions performed were irrelevant to the categorization judgment, responses were significantly faster when actions were compatible with the visual context. This compatibility effect was largely driven by faster pinch responses when objects were presented in use-compatible, as compared with move-compatible, contexts. The present study is the first to highlight the influence of visual scene on stimulus–response compatibility effects during semantic object processing. These data support the hypothesis that action evocation during conceptual object processing is biased toward context-relevant actions.     

Learning nonlinearly separable categories by inference and classification

Previous research suggests that learning categories by classifying new instances highlights information that is useful for discriminating between categories. In contrast, learning categories by making predictive inferences focuses learners on an abstract summary of each category (e.g., the prototype). To test this characterization of classification and inference learning further, the authors evaluated the two learning procedures with nonlinearly separable categories. In contrast to previous research involving cohesive, linearly separable categories, the authors found that it is more difficult to learn nonlinearly separable categories by making inferences about features than it is to learn them by classifying instances. This finding reflects that the prototype of a nonlinearly separable category does not provide a good summary of the category members. The results from this study suggest that having a cohesive category structure is more important for inference than it is for classification.