“Are there lexicons?” A study of lexical and semantic processing in word-meaning deafness suggests “yes”

A controversial issue in the cognitive neuroscience of language is the question whether independent lexical representations need to be included in cognitive models. Recent models claim to account for the available data without including phonological or orthographic lexicons. These models base their lexical decision (“Is it a word or not?”) either on familiarity of the input string or alternatively, on semantic information. These two alternatives were evaluated in a series of experiments with an individual suffering from word-meaning deafness. This is a rare disorder of auditory word comprehension which affects mapping of a word's phonology to its meaning. The participant, BB, was unaffected by the 'word-likeness' of nonwords with comparable accuracy for plausible and abstruse nonwords. She was further able to make lexical decisions despite her severe impairment in comprehending the word's meaning. Lexical and semantic processing were assessed on an item-specific basis providing a methodological advancement over previous studies. The comprehension tasks involved word-picture matching as well as definition tasks. The results suggest that BB's lexical decisions are based neither on familiarity of the input string nor on semantic information, which was largely unavailable. The only alternative are lexical representations on which she could base her decisions.