Action instruction word processing in the dog brain entails both auditory form identification and meaning representation.

Abstract

Dogs often show adequate behaviour to words directed to them. In humans, spoken word understanding requires both auditory word form identification and meaning attribution to that form. But how these contribute to lexical processing in dogs remains unknown. Auditory word form identification should take place in the auditory cortex and, if human-like, should not tolerate speech sound changes. Meaning attribution, in contrast, may also engage non-auditory, semantically relevant brain regions, and should evoke semantic representations. To seek evidence for both processes in dogs, here we used fMRI, comparing their neural responses to (1) instruction words for actions requiring locomotion (come, go) or not (stay, lay), (2) phonetically similar pseudowords (generated from words by altering a single speech sound), and (3) dissimilar non-words. Lexical responsivity, stronger activity to words relative to non-words, was identified not only in bilateral auditory but also in right motor and motor control regions. Semantic distances of action instruction words were reflected in representational dissimilarities in the bilateral auditory cortices. In most lexically responsive areas, responses to pseudowords were also stronger than to non-words but did not differ from those to words. The engagement of motor and motor control regions in response to action instruction words and the presence of auditory cortical semantic representations suggest that lexical processing in the dog brain goes beyond auditory word form identification and entails meaning attribution as well. The word-like processing of pseudowords shows that auditory word form representations in dogs are coarser-grained than in humans.