A new study has revealed some of the first evidence of how dogs also differentiate and process those various components of human speech.
Victoria Ratcliffe of the School of Psychology at the University of Sussex said that although they cannot say how much or in what way dogs understand information in speech from their study, they can say that dogs react to both verbal and speaker-related information and that these components appear to be processed in different areas of the dog's brain.
Previous studies showed that dogs have hemispheric biases-left brain versus right-when they process the vocalization sounds of other dogs. Ratcliffe and her supervisor David Reby said that it was a logical next step to investigate whether dogs show similar biases in response to the information transmitted in human speech. They played speech from either side of the dog so that the sounds entered each of their ears at the same time and with the same amplitude.
Ratcliffe said that the input from each ear is mainly transmitted to the opposite hemisphere of the brain and if one hemisphere is more specialized in processing certain information in the sound, then that information is perceived as coming from the opposite ear.
If the dog turned to its left, that showed that the information in the sound being played was heard more prominently by the left ear, suggesting that the right hemisphere is more specialized in processing that kind of information.
The researchers also observed general biases in dogs' responses to particular aspects of human speech. When presented with familiar spoken commands in which the meaningful components of words were made more obvious, dogs showed a left-hemisphere processing bias, as indicated by turning to the right. When the intonation or speaker-related vocal cues were exaggerated instead, dogs showed a significant right-hemisphere bias.
The study was published in the Cell Press journal Current Biology.