Orienting Asymmetries in Dogs’ Responses to Different Communicatory Components of Human Speech

Victoria F. Ratcliffe, David Reby

It is well established that in human speech perception the left hemisphere (LH) of the brain is specialized for processing intelligible phonemic (segmental) content (e.g., [1-3]), whereas the right hemisphere (RH) is more sensitive to prosodic (suprasegmental) cues [4, 5]. Despite evidence that a range of mammal species show LH specialization when processing conspecific vocalizations [6], the presence of hemispheric biases in domesticated animals' responses to the communicative components of human speech has never been investigated. Human speech is familiar and relevant to domestic dogs (Canis familiaris), who are known to perceive both segmental phonemic cues [7-10] and suprasegmental speaker-related [11, 12] and emotional [13] prosodic cues. Using the head-orienting paradigm, we presented dogs with manipulated speech and tones differing in segmental or suprasegmental content and recorded their orienting responses. We found that dogs showed a significant LH bias when presented with a familiar spoken command in which the salience of meaningful phonemic (segmental) cues was artificially increased but a significant RH bias in response to commands in which the salience of intonational or speaker-related (suprasegmental) vocal cues was increased. Our results provide insights into mechanisms of interspecific vocal perception in a domesticated mammal and suggest that dogs may share ancestral or convergent hemispheric specializations for processing the different functional communicative components of speech with human listeners.