Ad hoc category restructuring

Participants learned to classify seemingly arbitrary words into categories that also corresponded to ad hoc categories (see, e.g., Barsalou, 1983). By adapting experimental mechanisms previously used to study knowledge restructuring in perceptual categorization, we provide a novel account of how experimental and preexperimental knowledge interact. Participants were told of the existence of the ad hoc categories either at the beginning or the end of training. When the ad hoc labels were revealed at the end of training, participants switched from categorization based on experimental learning to categorization based on preexperimental knowledge in some, but not all, circumstances. Important mediators of the extent of that switch were the amount of performance error experienced during prior learning and whether or not prior knowledge was in conflict with experimental learning. We present a computational model of the trade-off between preexperimental knowledge and experimental learning that accounts for the main results.     

Ad hoc Reviewers for the Journal of Motor Behavior

The study of sign languages provides a promising vehicle for investigating language production because the movements of the articulators in sign are directly observable. Movement of the hands and arms is an essential element not only in the lexical structure of American Sign Language (ASL), but most strikingly, in the grammatical structure of ASL: It is in patterned changes of the movement of signs that many grammatical attributes are represented. The “phonological? (formational) structure of movement in ASL surely reflects in part constraints on the channel through which it is conveyed. We evaluate the relation between one neuromotor constraint on movement–regulation of final position rather than of movement amplitude–and the phonological structure of movement in ASL. We combine three-dimensional measurements of ASL movements with linguistic analyses of the distinctiveness and predictability of the final position (location) versus the amplitude (length). We show that final position, not movement amplitude, is distinctive in the language and that a phonological rule in ASL predicts variation in movement amplitude–a development which may reflect a neuromuscular constraint on the articulatory mechanism through which the language is conveyed.     

Strategies for generating multiple instances of common and ad hoc categories

In a free-emission procedure participants were asked to generate instances of a given category and to report, retrospectively, the strategies that they were aware of using in retrieving instances. In two studies reported here, participants generated instances for common categories (e.g. fruit) and for ad hoc categories (e.g., things people keep in their pockets) for 90 seconds and for each category described how they had proceeded in doing so. Analysis of the protocols identified three broad classes of strategy: (1) experiential, where memories of specific or generic personal experiences involving interactions with the category instances acted as cues; (2) semantic, where a consideration of abstract conceptual characteristics of a category were employed to retrieve category exemplars; (3) unmediated, where instances were effortlessly retrieved without mediating cognitions of which subjects were aware. Experiential strategies outnumbered semantic strategies (on average 4 to 1) not only for ad hoc categories but also for common categories. This pattern was noticeably reversed for ad hoc categories that subjects were unlikely to have experienced personally (e.g. things sold on the black market in Russia). Whereas more traditional accounts of semantic memory have favoured decontextualised abstract representations of category knowledge, to the extent that mode of access informs us of knowledge structures, our data suggest that category knowledge is significantly grounded in terms of everyday contexts where category instances are encountered.     

Relational categories are more mutable than entity categories

Across three experiments, we explore differences between relational categories—whose members share common relational patterns—and entity categories, whose members share common intrinsic properties. Specifically, we test the claim that relational concepts are more semantically mutable in context, and therefore less stable in memory, than entity concepts. We compared memory for entity nouns and relational nouns, tested either in the same context as at encoding or in a different context. We found that (a) participants show better recognition accuracy for entity nouns than for relational nouns, and (b) recognition of relational nouns is more impaired by a change in context than is recognition of entity nouns. We replicated these findings even when controlling for factors highly correlated with relationality, such as abstractness–concreteness. This suggests that the contextual mutability of relational concepts is due to the core semantic property of conveying relational structure and not simply to accompanying characteristics such as abstractness. We note parallels with the distinction between nouns and verbs and suggest implications for lexical and conceptual structure. Finally, we relate these patterns to proposals that a deep distinction exists between words with an essentially referential function and those with a predicate function.     

Cody's categories

Of the two main interpretations of Spinoza's theory of the identity of the attributes, in particular those of Thought and Extension, the objective interpretation is now almost universally preferred to the subjective. Rejection of the subjective interpretation, according to which the attributes are merely our ways of cognizing a reality whose real essence remains unknown, is certainly justified, but the objective theory comes too near to replacing the identity by a mere correlation of différents to be quite satisfactory. Is it not better to say that Thought and Extension represent two complementary conceptions of reality which are both correct? Yes, but in saying so some commentators ascribe to mind, as Spinoza conceives it, an unplausibly abstract status. An alternative proposal is made as to a way in which Spinoza might be right in essentials, though it requires that a certain tension in Spinozism as to the nature of body be resolved in a particular direction.     

Natural categories

The hypothesis of the study was that the domains of color and form are structured into nonarbitrary, semantic categories which develop around perceptually salient “natural prototypes.” Categories which reflected such an organization (where the presumed natural prototypes were central tendencies of the categories) and categories which violated the organization (natural prototypes peripheral) were taught to a total of 162 members of a Stone Age culture which did not initially have hue or geometric-form concepts. In both domains, the presumed “natural” categories were consistently easier to learn than the “distorted” categories. Even when not central, natural prototype stimuli tended to be more rapidly learned and more often chosen as the most typical example of the category than were other stimuli. Implications for general differences between natural categories and the artificial categories of concept formation research were discussed.     

Inference using categories

How do people use category membership and similarity for making inductive inferences? The authors addressed this question by examining the impact of category labels and category features on inference and classification tasks that were designed to be comparable. In the inference task, participants predicted the value of a missing feature of an item given its category label and other feature values. In the classification task, participants predicted the category label of an item given its feature values. The results from 4 experiments suggest that category membership influences inference even when similarity information contradicts the category label. This tendency was stronger when the category label conveyed class inclusion information than when the label reflected a feature of the category. These findings suggest that category membership affects inference beyond similarity and that category labels and category features are 2 different things.     

Abstract coherent categories

Many studies have demonstrated the importance of the knowledge that interrelates features in people's mental representation of categories and that makes our conception of categories coherent. This article focuses on abstract coherent categories, coherent categories that are also abstract because they are defined by relations independently of any features. Four experiments demonstrate that abstract coherent categories are learned more easily than control categories with identical features and statistical structure, and also that participants induced an abstract representation of the category by granting category membership to exemplars with completely novel features. The authors argue that the human conceptual system is heavily populated with abstract coherent concepts, including conceptions of social groups, societal institutions, legal, political, and military scenarios, and many superordinate categories, such as classes of natural kinds.     

Achromatic color categories

Sternheim and Boynton’s (1966) continuous judgmental color-naming technique was used to assess the elemental nature of achromatic colors. Results from three subjects indicate that the names “black” and “white” are necessary and sufficient to describe achromatic test lights associated with the name “gray.” On the basis of the criteria that establishes a color as elemental, black and white were confirmed as elemental, whereas gray was not. These findings support the assumption of various opponent processing models that there are only two elemental achromatic sensations. In addition, the results support Hering’s (1920) view that black and white differ from the paired-chromatic opponent colors in that they are not mutually exclusive.     

Learning time-varying categories

Many kinds of objects and events in our world have a strongly time-dependent quality. However, most theories about concepts and categories either are insensitive to variation over time or treat it as a nuisance factor that produces irrational order effects during learning. In this article, we present two category learning experiments in which we explored peoples’ ability to learn categories whose structure is strongly time-dependent. We suggest that order effects in categorization may in part reflect a sensitivity to changing environments, and that understanding dynamically changing concepts is an important part of developing a full account of human categorization.     

Variation within categories

Two aspects of variation within categories, relating to different models of categorization, were investigated — frequency of dimensional values and typicality differences within values. The influence of range of typicality experienced during learning and of informational value of feedback was also studied. Finally, differential forgetting of values was examined.In the experiment subjects learned to categorize faces, and then performed a classification test task and pairwise comparisons of faces. A variety of dependent variables was employed, including the galvanic skin response (GSR).Typicality and frequency of values appeared to influence categorization performance independent of each other. It was concluded that both prototype distance models and frequency models explain different aspects of variation within the same categories, and that models of classification should account for frequency of values in contrasting categories. Results showed furthermore (1) the influence of typicality range on the extension of a category; (2) no influence of specific feedback regarding representativeness of a face; (3) less decay with more important values; and (4) a positive relationship between uncertainty reduction and GSR.     

Cognitive categories and memory span: I. Shifting between categories

Broadbent and Gregory's hypothesis that shifting selection between cognitive classes is at least inefficient is tested by varying the number of transitions from consonants to digits and back in a mixed list memory span situation. No orderly decrease is found as a function of the number of transitions, which renders the attention hypothesis unlikely. An alternative position in terms of interference theory could explain the data qualitatively. Tests of further predictions of this theory need first an estimate of the degree of difference between cognitive classes.     

Case-like categories in children: The actor and some related categories

Case categories were investigated using a method in which pictures are presented accompanied by a sentence describing the scene: Preschool children learn to put tokens on the objects in the pictures according to the role each object plays in the scene as described. Generalization trials explore what the children include within the various roles. Children rapidly learn to associate tokens with case-like categories during the training phase, and readily transfer to new stimuli in generalization trials. The experiments demonstrate that children have a broad Actor category. The Actor “does” the action, and Actors are not necessarily animate. However, animacy is a class property of stimuli to which the children were very sensitive. There was evidence that User and Instrument are subcategories of Actor that are differentiated only when a sentence contains both. The data also suggest a Locative category, and Patient as a category of the grammatical object. Finally, the children appeared to treat subjects of predicate adjectives as a separate category, here called the Subject of Attribution, distinct from Actor, and functionally independent of objects of transitive verbs.