Zipf’s law in non-fluent aphasia

We studied Zipf’s law in the spontaneous speech of four people with non-fluent aphasia, and compared that to the spontaneous speech of four speakers from the Corpus of Spoken Dutch. Our results show no worse fit to Zipf’s law for aphasic compared to healthy speech but only a difference in slope. We argue that the fact that Zipf’s law is unaffected in people with aphasia, who suffer from problems with word retrieval rather than word storage, suggests that it is the organization of the mental lexicon that renders speech to conform to Zipf’s law and not the word retrieval system.