Language-like properties in the vocal behavior of animals

The relation between the vocal capacities of animals and those of humans is a long-standing topic of interest for scientists, philosophers, and lay people alike. While similar neural and physiological substrates underlie the production of vocal signals in humans and animals, the most celebrated and prototypical aspects of language are cognitive phenomena that go far beyond speech sensorimotor processes. These include a subset of features that have begun to be systematically investigated in nonhuman animals, namely: (i) the presence of statistical laws, (ii) hierarchical syntactic rules, and (iii) the capacity for meaning and reference. Here we review recent progress describing and quantifying language-like structure in animal vocalizations. We highlight agreement and disagreement about the similarities that may exist between human language and animal vocal repertoires, with an eye toward what these phenomena may reveal about the evolution of language and its neural control.