Academic journal article Memory & Cognition

Effects of Classification Context on Categorization in Natural Categories

Academic journal article Memory & Cognition

Effects of Classification Context on Categorization in Natural Categories

Article excerpt

The patterns of classification of borderline instances of eight common taxonomic categories were examined under three different instructional conditions to test two predictions: first, that lack of a specified context contributes to vagueness in categorization, and second, that altering the purpose of classification can lead to greater or lesser dependence on similarity in classification. The instructional conditions contrasted purely pragmatic with more technical/quasi-legal contexts as purposes for classification, and these were compared with a no-context control. The measures of category vagueness were between-subjects disagreement and within-subjects consistency, and the measures of similarity-based categorization were category breadth and the correlation of instance categorization probability with mean rated typicality, independently measured in a neutral context Contrary to predictions, none of the measures of vagueness, reliability, category breadth, or correlation with typicality were generally affected by the instructional setting as a function of pragmatic versus technical purposes. Only one subcondition, in which a situational context was implied in addition to a purposive context, produced a significant change in categorization. Further experiments demonstrated that the effect of context was not increased when participants talked their way through the task, and that a technical context did not elicit more all-or-none categorization than did a pragmatic context These findings place an important boundary condition on the effects of instructional context on conceptual categorization.

A phenomenon of major importance for psychological theories of concepts is the vagueness of many of our conceptual categories. Although every category can be said to have clear members (for example, a chair is clearly a type of furniture) and clear nonmembers (a cucumber is clearly not a type of furniture), there are also instances that are borderline to a category. For instance, when asked to decide whether rugs, paintings, or televisions are types of furniture, people are frequently uncertain about the answer. There is a vagueness in our use of common language terms that arguably makes such questions undecidable. The problem of vagueness poses serious threats to many accounts of the semantics of natural language (Keefe & Smith, 1996; Osherson & Smith, 1997), so the issue of what gives rise to the phenomenon is of central importance to theories of cognition.

There have been many demonstrations of vagueness. For example, McCloskey and Glucksberg (1978) presented two groups of students with lists of words, each list headed by a category name, such as "fruit" or "fish." One group was asked to give typicality ratings, identifying how typical or representative each word was of the category as a whole. The other group made a simple yes-no categorization decision about each word and returned 4 weeks later to make the same decision again. Many items in the lists showed high levels of disagreement between participants and poor test-retest reliability or consistency. These items also tended to be borderline in terms of their rated typicality in the category.

In a subsequent reanalysis of McCloskey and Glucksberg's (1978) data, Hampton (1998) showed that categorization probability for an item was closely related to rated typicality by a simple, monotonically increasing threshold function. List items that deviated from this standard function tended to be unfamiliar, or they might be parts or properties of an instance rather than instances themselves. For biological categories, particular items also could deviate from the function if they had the appearance of a category member without technically belonging to the category or, conversely, if they technically belonged to a category but did not share its appearance features. From this analysis, Hampton (1998) argued that categorization decisions are to a large extent based on the same "family resemblance" semantic information that is used in judging typicality: An item is judged to be a category member if the similarity between the item and the prototype for that category passes some threshold value. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.