Do Goats Recognise Humans Cross-Modally?

Abstract

Recognition plays a key role in the social lives of gregarious species, enabling animals to distinguish among social partners and tailor their behaviour accordingly. As domesticated animals regularly interact with humans, as well as members of their own species, we might expect mechanisms used to discriminate between conspecifics to also apply to humans. Given that goats can combine visual and vocal cues to recognize one another, we investigated whether this cross-modal recognition extends to discriminating among familiar humans. We presented 28 goats with facial photographs of familiar people and two repeated playbacks of a voice, either congruent (from the same person) or incongruent with that photograph (from a different person). When cues were incongruent, violating their expectations, we expected goats to respond faster and for longer after playbacks and show increases in physiological arousal (increased heart rate and/or decreased heart rate variability). We found the increase in latency that goats took to respond as the playback series progressed was greater when the face and voice were incongruent. As differences were not as predicted and only observed in one response measured, our evidence is tentative, but the variation in latency to look between congruency conditions suggests goat cross-modal recognition extends to humans. If this is the case, not only would this further demonstrate the flexibility of complex recognition systems to discriminate among members of a very different species, but indicates goats can produce mental representations for familiar people, a key component of individual recognition.