Sound symbolism facilitates interspecies communication between humans and domestic dogs (Canis familiaris)

The evolution of human communication likely centred, in part, on shared intuitions about the mapping of sound to meaning. These sound-meaning intuitions, known as sound symbolism, can be seen for example in the bouba-kiki effect, where nonsense words carry inherent meaning about their likely referents (here, rounded vs. angular objects respectively). In our paper we suggest for the first time that sound symbolism can afford successful interspecies communication between humans and animals in certain circumstances. Over four investigations, including replications, we show that humans use sound symbolism significantly and pervasively to attempt to convey meaning to domestic dogs (Canis familiaris), specifically, by exploiting vocal prosody to signal elevation in space. In Study 1 we analysed recordings of amateur dog owners commanding their dogs to move upwards (e.g., "stand") or downwards (e.g., "down"), finding higher mean pitch (fundamental frequency, f₀) in the former versus the latter. In Studies 2 and 3a, we replicated this in competitive dog owners, both in self-report, and in acoustic voice-analyses recorded in competition. In addition, professionals also used further sound symbolism beyond amateurs, in their commands for the dog to "sit" (using higher pitch to denote sit up vs. sit down). Finally, in Study 3b, we demonstrate that sound symbolism appears to be mutually understood by dogs in certain useful circumstances. Dogs were faster to enact "down" commands with prosodic sound symbolism, compared to without, demonstrating that sound symbolism may sometimes underlie successful inter-species communication.