Dogs' reactions to motivations and emotions in conspecific and heterospecific vocalizations.

Vocalizations convey information about both emotional valence (negative/positive) and motivational states (hostile/non-hostile). However, it remains unclear which of these dimensions primarily determines what the listener decodes from vocalizations as social messages, guiding their reaction (approach/withdraw). To test this question, we presented agonistic (negative|hostile), play/comfort (positive|non-hostile), and distress sounds (negative|non-hostile) to dogs. In Study 1, the motivational state encoded in conspecific calls better explained dogs' reactions than emotional valence. Distress calls evoked faster approaches but slower withdrawal than agonistic calls, indicating that dogs primarily decode conspecific social messages based on the caller's motivation. In Study 2, we tested cross-species decodability with chimpanzee and human calls and speech. Neither the callers' motivational state nor emotional valence explained dogs' reactions, which did not support predictions based on Morton's rules and other proposed universal principles of emotion encoding. These findings suggest that the caller's motivation may have been more significant in close-contact call evolution than emotions, and the mechanisms underlying the processing of conspecific vocalizations do not directly generalize to cross-species vocalizations. Consequently, decoding social messages from vocalizations may rely less on universal rules than previously thought.