Barbara C. Malt

Correlated properties in natural categories.

In most models of categorization, the properties of category members are assumed to be independent of one another. Several sources of evidence suggest, however, that this assumption may be false, and furthermore, that the nonindependence of properties may have important consequences for categorization. In the experiments presented here, it was demonstrated that properties of natural categories occur in systematic relation to one another rather than independently. Property relations did not seem to influence typicality judgments when the potential impact was assessed using models similar to those in the concept-learning literature. In a further experiment, under different conditions, property relations did influence typicality, suggesting that knowledge of such relationships may mainly concern certain particularly salient or functional combinations.

Category Coherence in Cross-Cultural Perspective

Abstract Cognitive psychologists and cognitive anthropologists alike have been concerned with how the human mind divides entities in the world into categories. Cognitive psychologists have recently begun approaching this issue by asking a question long of interest to anthropologists: To what extent are the categories given by structure in the environment, and to what extent are they created through constructive processes on the part of the human categorizer? Despite this shared question, relatively little of the data available in the anthropological literature has become familiar to psychologists. Psychologists stand to benefit from greater acquaintance with this literature, since the cross-cultural studies have often addressed the relative roles of structure in the environment vs constructive processes by the observer more directly than psychological studies have. Furthermore, cross-cultural data provide a unique opportunity to separate culture-specific from universal aspects of categorization. This paper sketches positions on the nature of category formation that have been put forth in the psychological literature. It then reviews in detail four areas of anthropological research that are relevant to evaluating the psychological perspectives. The cross- cultural data provide substantial constraints for theories of category coherence.

Do artifact concepts have cores

Mental representations of everyday categories include many features that are neither necessary nor sufficient for membership in the category. Recent proposals have suggested, however, that they may also contain “core” features that are critical to category membership. Several researchers have suggested that for artifacts (chair, pencil, toy, etc.), function serves as the concept core. We conducted four experiments testing whether function is the primary determinat of membership in artifact categories. We found that some objects that do possess the function associated with a category are excluded from category membership, and some objects that do not possess the standard function are still considered to belong to the category. We also found that membership decisions were more influenced by physical features of the objects than by functions. These results suggest that function may not provide a core for artifact concepts, and they cast doubt on the appropriateness of the core hypothesis for at least some common concepts.

The role of familiarity in determining typicality

Ashcraft (1978b) found that people tend to know more properties of instances they rate as typical of a category than of instances they rate as atypical. This suggests that variations in typicality result from variations in familiarity. Three experiments are presented that challenge or qualify this suggestion. Experiment 1 showed that subjects sometimes produce more properties for items they rate as low in typicality. Experiment 2 showed that in a large, random sample of items, there was a tendency to produce fewer properties for atypical items, but Experiment 3 indicated that part of the reason for this result was a response bias to assign low typicality ratings to unfamiliar words, rather than a reflection of low perceived typicality of the referents themselves. These results suggest that variations in typicality can exist independent of variations in familiarity, although familiarity may also play a role.

An on-line investigation of prototype and exemplar strategies in classification.

Although prototype- and exemplar-based models of categorization are very different in character, they have proved difficult to distinguish experimentally. The research described here presents a priming technique for assessing the type of information retrieved at the moment that a categorization decision is made. This technique avoids many of the problems inherent in the standard paradigms. Data from six experiments are presented that demonstrate the usefulness of the technique and also address basic questions about the categorization process. Results bolster previous suggestions that categorization strategies may be mixed within a single experimental task and highlight the need for more specific predictions about when each strategy will come into play.

Universality and language specificity in object naming

Abstract Rather than having universal linguistic categories for sets of common objects, languages develop their own, idiosyncratic naming patterns for them. Accounting for these patterns requires reference not only to the understanding of stimulus properties by individual speakers of a language, but also to the linguistic and cultural histories of the language they speak. To better understand how these two sources of influence work together to produce linguistic categories, we examined the relations among linguistic categories for 60 common containers for speakers of English, Spanish, and Chinese. We discriminated among several possibilities that imply different relative contributions of the two sources of influence. No single type of relation dominated; the contributions of the two influences varied across different parts of the container domain. We suggest that perception of stimulus properties by individuals interacts with linguistic and cultural histories, but their interaction is constrained by structure in the stimulus space.

Predicting Features for Members of Natural Categories When Categorization Is Uncertain

An important function of concepts to allow prediction of unseen features. A Bayesian account of feature prediction suggests that people will consider all the categories an object could belong to when they judge the likelihood that the object has a feature. The judgment and decision literature suggests that they may instead use a simpler heuristic in which they consider only the most likely category. In 3 experiments, no evidence was found that participants took into account alternative categories as well as the most likely one when they judged feature probabilities for familiar objects in meaningful contexts. These results, in conjunction with those of Murphy and Ross (1994), suggest that although people may consider alternative categories in certain limited situations, they often do not. Reasons for why the use of alternative categories may be relatively rare are discussed, and conditions under which people may take alternative categories into account are outlined.

Features and beliefs in the mental representation of categories

Simple concepts such as chair and bird are central to human cognition, but the nature of these mental representations is unclear. Accounts based on probabilistically associated features fail to account for certain observations about category membership judgments. On the other hand, the possibility that concepts consist of or even include defining features has received little empirical support. The work reported here argues that certain phenomena may not reflect the actual presence of defining features, but rather only the presence of a belief in such features. Further, concepts will not be uniform with respect to this belief: Some concepts will include a belief in defining features, but others will not. Five experiments explore these possibilities through two different experimental tasks based on judgments of sentence acceptability. Results support the idea that concepts include beliefs about the nature of the categories they represent, and that certain concepts (notably, many natural kind concepts) differ from others (notably, many common artifact concepts) in the nature of the beliefs held, even though defining features may not be explicitly represented in either.

Artifacts are not ascribed essences, nor are they treated as belonging to kinds

We evaluate three theories of categorisation in the domain of artifacts. Two theories are versions of psychological essentialism; they posit that artifact categorisation is a matter of judging membership in a kind by appealing to a belief about the true, underlying nature of the object. The first version holds that the essence can be identified with the intended function of objects. The second holds that the essence can be identified with the creator’s intended kind membership. The third theory is called ‘minimalism”. It states that judgements of kind membership are based on beliefs about causal laws, not beliefs about essences. We conclude that each theory makes unnecessary assumptions in explaining how people make everyday classifications and inductions with artifacts. Essentialist theories go wrong in assuming that the belief that artifacts have essences is critical to categorisation. All theories go wrong in assuming that artifacts are treated as if they belong to stable, fixed kinds. Theories of artifact categorisation must contend with the fact that artifact categories are not stable, but rather depend on the categorisation task at hand.

Talking About Walking: Biomechanics and the Language of Locomotion

What drives humans around the world to converge in certain ways in their naming while diverging dramatically in others? We studied how naming patterns are constrained by investigating whether labeling of human locomotion reflects the biomechanical discontinuity between walking and running gaits. Similarity judgments of a student locomoting on a treadmill at different slopes and speeds revealed perception of this discontinuity. Naming judgments of the same clips by speakers of English, Japanese, Spanish, and Dutch showed lexical distinctions between walking and running consistent with the perceived discontinuity. Typicality judgments showed that major gait terms of the four languages share goodness-of-example gradients. These data demonstrate that naming reflects the biomechanical discontinuity between walking and running and that shared elements of naming can arise from correlations among stimulus properties that are dynamic and fleeting. The results support the proposal that converging naming patterns reflect structure in the world, not only acts of construction by observers.