Parallel or serial activation of word forms in speech production? Neurolinguistic evidence from an aphasic patient.

We report the oral picture naming performance of the German aphasic MW who presented with frequent meaning related word substitutions (e.g. tiger ==> lion) and word finding blockings (omissions) while his phonological capacities at the single word level were nearly preserved. Targets were controlled for their 'semantic competitiveness', that is, whether there exist closely meaning related lexical competitors or not. Semantic errors were far more numerous with the highly competitive targets than with the low competitive ones. However, omissions were more frequent with the low competitive items so that the sum of the semantic errors and of the omissions was comparable in both conditions. This inverse and compensatory relationship suggests that both error types are not mutually independent. The found pattern is at odds with serial psycholinguistic theories which locate word selection (and misselection) and word form access (and blockings) at different and serially connected stages of word production but supports theories which allow for a parallel architecture in lexical activation and selection involving the word form level.