Evidence from aphasia is considered that leads to a distinction between abstract and concrete thought processes and hence for a distinction between rules and similarity. It is argued that perceptual classification is inherently a rule-following procedure and these rules are unable to be followed when a patient has difficulty with name comprehension and retrieval.
Goldstein reported multiple cases of failure to categorise colours in patients that he termed amnesic or anomic aphasics. These patients have a particular difficulty in producing perceptual categories in the absence of other aphasic impairments. We hold that neuropsychological evidence supports the view that the task of colour categorisation is logically impossible without labels.
The purpose of the commentary is not to contradict HIT but rather to question whether its increase in predictive power outweighs the decrease in parsimony. For the refutable aspects of HIT, a simpler model for naming appears to achieve as much. Both models better fit the facts concerning naming performance than describe category-specificity.
The question of whether colour categorisation is determined by nontrivial constraints (i.e., universal neurophysiological properties of visual neurons) is an empirical issue concerning the organisation of the internal colour space. Rosch has provided psychological evidence that categories are organised around focal colours and that the organisation is universal; this commentary reconsiders that evidence.