Nick Braisby

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, LEWs 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. LEWs 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.

Compositionality and the Modelling of Complex Concepts

The nature of complex concepts has important implications for the computational modelling of the mind, as well as for the cognitive science of concepts. This paper outlines the way in which RVC – a Relational View of Concepts – accommodates a range of complex concepts, cases which have been argued to be non-compositional. RVC attempts to integrate a number of psychological, linguistic and psycholinguistic considerations with the situation-theoretic view that information-carrying relations hold only relative to background situations. The central tenet of RVC is that the content of concepts varies systematically with perspective. The analysis of complex concepts indicates that compositionality too should be considered to be sensitive to perspective. Such a view accords with concepts and mental states being situated and the implications for theories of concepts and for computational models of the mind are discussed.

Why the Dynamical Hypothesis Cannot Qualify as a Law of Qualitative Structure

van Gelder presents the Dynamical Hypothesis as a novel law of qualitative structure to compete with Newell & Simon’s (1976) Physical Symbol Systems Hypothesis. Unlike Newell & Simon’s Hypothesis, the Dynamical Hypothesis fails to provide necessary and sufficient conditions for cognition. Furthermore, imprecision in the statement of the Dynamical Hypothesis render it unfalsifiable.

Semantics versus pragmatics in colour categorization

We argue that the confusing pattern of evidence concerning colour categorization reported by Saunders & van Brakel is unsurprising. On a perspectival view, categorization may follow semantic or pragmatic attributes. Colour lacks clear semantic attributes; as a result categorization is necessarily pragmatic and context-sensitive. This view of colour categorization helps explain the developmental delay in colour naming.