Basic-level Object Research Articles

Basic level categorization in seven- and nine-month-old infants.

ABSTRACTThe current reliance on linguistic data for inferences about the concept–word relationship has led to serious questions being raised regarding the existence and facilitative role of prelinguistic categories in early word learning. In three experiments a multiple habituation paradigm was used to examine the ability of 7- and 9-month-old prelinguistic infants to form a natural, basic-level object category. In Experiment 1, 9-month-old infants appeared to form a category of bird, but only when habituated to prototypical exemplars as opposed to poor exemplars. Discriminability between prototypical habituation exemplars and test stimuli was demonstrated in Experiment 2. In Experiment 3, 7-month-olds did not form a category of bird when habituated to prototypes. These findings constitute independent evidence for the existence of a linguistically relevant nonlinguistic category prior to the onset of word comprehension. Moreover, formation of prelinguistic categories appears to be facilitated by exposure to prototypes. Such goodness-of-exemplar effects suggest a structural similarity between infants' prelinguistic categories and early semantic categories. Finally, nonlinguistic categorization of natural basic-level objects, as represented in line drawings, appears to emerge between 0;7 and 0;9.

Objects, parts, and categories.

Concepts may be organized into taxonomies varying in inclusiveness or abstraction, such as furniture, table, card table or animal, bird, robin. For taxonomies of common objects and organisms, the basic level, the level of table and bird, has been determined to be most informative (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976). Psychology, linguistics, and anthropology have produced a variety of measures of perception, behavior, and communication that converge on the basic level. Here, we present data showing that the basic level differs qualitatively from other levels in taxonomies of objects and of living things and present an explanation for why so many measures converge at that level. We have found that part terms proliferate in subjects' listings of attributes characterizing category members at the basic level, but are rarely listed at a general level. At a more specific level, fewer parts are listed, though more are judged to be true. Basic level objects are distinguished from one another by parts, but members of subordinate categories share parts and differ from one another on other attributes. Informants agree on the parts of objects, and also on relative "goodness" of the various parts. Perceptual salience and functional significance both appear to contribute to perceived part goodness. Names of parts frequently enjoy a duality not evident in names of other attributes; they refer at once to a particular appearance and to a particular function. We propose that part configuration underlies the various empirical operations of perception, behavior, and communication that converge at the basic level. Part configuration underlies the perceptual measures because it determines the shapes of objects to a large degree. Parts underlie the behavioral tasks because most of our behaviors is indirect toward parts of objects. Labeling appears to follow the natural breaks of perception and behavior; consequently, part configuration also underlies communication measures. Because elements of more abstract taxonomies, such as scenes and events, can also be decomposed into parts, this analysis provides a bridge to organization in other domains of knowledge. Knowledge organization by parts (partonomy) is contrasted to organization by kinds (taxonomy). Taxonomies serve to organize numerous classes of entities and to allow inference from larger sets to sets included in them. Partonomies serve to separate entities into their structural components and to organize knowledge of function by components of structure. The informativeness of the basic level may originate from the availability of inference from structure to function at that level.