Should we see to understand what we hear? – Playback dog barks to sightless and sighted human listeners

The wild canids rarely bark, and this occurs only in a few social situations, e.g., aggression between groups, or while defending the den. Whereas family dogs bark frequently in several contexts. One possible hypothesis explaining this hypertrophisation of barking is that the barking plays a crucial role in dog-human communication, and possibly humans preferred and thus selected for the more barky dogs during domestication. For this to happen, the dogs’ bark should have different acoustical parameters depending on the motivational state of the individual and/or the context. In an earlier study, we showed that human listeners were able to categorize dog bark samples played back for them. They were able to classify the situations of barking, regardless of their former experiences with dogs. The listeners described the possible motivational states of the given barking dog quite accurately. In this study we explored if the listeners’ visual information on dogs had an effect on their ability to categorize the barks in situations and describe the possible motivational states of the dogs. We conducted a playback experiment with human sightless, and sighted subjects using dog barks as stimuli. We compared the performances of born-sightless subjects and those who lost their sight during their lives. We found that the sightless (regardless when they lost their sight) and sighted subjects could categorise the barks in situations significantly above the chance level, and their performances did not differ significantly. The subjects described the motivational state of dogs quite similarly. Our findings suggest that the humans are able to gain context- and motivational state-specific information from hearing the barks regardless they have or have not visual information about dogs.

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