Goat Discrimination of Emotional Valence in the Human Voice

Reading another animals emotional state can enable receivers to anticipate their behavioural motivations, which is important in guiding interactions with that individual. For species living closely alongside humans, the emotional cues that people express can be almost as informative as those of conspecifics. Goats can discriminate differences in emotional valence present in another goats calls, and we investigated whether this ability extends to human speech. We presented goats with a habituation-dishabituation-rehabituation paradigm, where they experienced multiple playbacks of a familiar or unfamiliar human voice conveying a single emotional valence (e.g., angry; habituation phase), before the valence of the voice changed (e.g., happy; dishabituation phase) and then reversed again in-line with the habituation phase (e.g., angry; rehabituation phase). Over the habituation phase, goat behavioural responses decreased, showing evidence of having habituated to the playback stimuli presented. Following a change in emotional valence (dishabituation phase), although goats were overall less likely to respond, those that did looked for longer, suggesting they had perceived the shift in emotional content conveyed in human voice playbacks. We found no changes in physiological arousal (heart rate or heart rate variability) with shifts in playback valence. Goats, as a domesticated species, may have developed a sensitivity to our cues over their long association with humans, but the differences in individual behaviour towards the playback paradigm could highlight a role for learning and individual experience in particular on interspecific emotional communication.