Similarity and categorisation: neuropsychological evidence for a dissociation in explicit categorisation tasks.

A series of experiments are reported on a patient (LEW) with difficulties in naming. Initial findings indicated severe impairments in his ability to freesort colours and facial expressions. However, LEW's performance on other tasks revealed that he was able to show implicit understanding of some of the classic hallmarks of categorical perception; for example, in experiments requiring the choice of an odd-one-out, the patient chose alternatives dictated by category rather than by perceptual distance. Thus, underlying categories appeared normal and boundaries appeared intact. Furthermore, in a two-alternative forced-choice recognition memory task, performance was worse for within-category decisions than for cross-category decisions. In a replication of the study of Kay and Kempton [Kay, P., Kempton, W., 1984. What is the Sapir-Whorf hypothesis? American Anthropologist 86, 65-78], LEW showed that his similarity judgements for colours could be based on perceptual or categorical similarity according to task demands. The consequences for issues concerned with perceptual categories and the relationship between perceptual similarity and explicit categorisation are considered; we argue for a dissociation between these kinds of judgements in the freesort tasks. LEW's inability to make explicit use of his intact (implicit) knowledge is seen as related to his language impairment.

Why is colour naming difficult?

A suggestion exists in the child language literature that the meanings of natural kind terms are acquired before the meanings of colour terms. Explanations have typically claimed that object terms are more salient than property terms. Such explanations, however, tend to ignore the fact that natural kind terms refer to categories with sharp, clear boundaries while colour terms refer to categories with unclear or variable boundaries. Nonetheless, there has been little evidence to show that the delay in the acquisition of colour terms arises from these semantic properties. This study compares natural kind and colour naming (and corresponding comprehension) by 48 children, ranging in age from 3;0 to 5;5. The results suggest that, contra the salience view, the apparent delay in colour naming may be explained on solely semantic grounds.

Essentialism, word use, and concepts.

The essentialist approach to word meaning has been used to undermine the fundamental assumptions of the cognitive psychology of concepts. Essentialism assumes that a word refers to a natural kind category in virtue of category members possessing essential properties. In support of this thesis, Kripke and Putnam deploy various intuitions concerning word use under circumstances in which discoveries about natural kinds are made. Although some studies employing counterfactual discoveries and related transformations appear to vindicate essentialism, we argue that the intuitions have not been investigated exhaustively. In particular, we argue that discoveries concerning the essential properties of whole categories (rather than simply of particular category members) are critical to the essentialist intuitions. The studies reported here examine such discovery contexts, and demonstrate that words and concepts are not used in accordance with essentialism. The results are, however, consistent with "representational change" views of concepts, which are broadly Fregean in their motivation. We conclude that since essentialism is not vindicated by ordinary word use, it fails to undermine the cognitive psychology of concepts.

Young children's understanding of counting and cardinality.

4-year-old's knowledge of counting and cardinality--the last count word reached represents the numerosity of the set--was tested in 2 experiments. Experiment 1 investigated the nature of early cardinality responses by presenting different forms of the cardinality question before, after, and before and after the child counted. Both type and time of question has large effects. Experiment 2 examined whether children of this age could recognize errors in 4 counting procedures and whether they would reject a cardinality response arrived at through a mistaken counting procedure. The children were very good at recognizing a standard counting procedure as correct. They had only limited success at treating procedures that violated the stable order of count words or violated the one-one correspondence between count word and object as incorrect. They lacked an understanding of the order irrelevance in that they judged valid, nonstandard counting orders as incorrect. The children did not seem to link their evaluation of a cardinality response with their evaluation of the counting procedure used to reach that response. The results do not indicate that counting principles initially govern the child's acquisition of counting knowledge. They are consistent with the suggestion that early cardinality responses are last-word responses.