Humans learn to speak by listening to acoustic models, forming auditory templates, and then learning to produce vocalizations that match the template. A similar pattern has been found for many songbirds, but most other animal species are thought to inherit vocal motor programs and to develop vocalizations with an acoustic structure that is not influenced by auditory feedback. The evolutionary origins of vocal learning among our hominid ancestors are obscure, because no non-human primates show strong evidence for vocal learning. Along with three taxa of birds, five mammalian groups have evolved vocal learning: bats, cetaceans (or dolphins and whales), elephants, humans and seals. Some of the best evidence involves animals reared by humans that learn to imitate speech sounds. These abilities are well known for parrots and some songbirds, but also have been demonstrated for a harbor seal and an Asian elephant. The songs of some wild birds and mammals also provide evidence of learning – for example all adult males within a population of humpback whales sing similar songs at one time, and track changes in the song over months and years. As with some songbirds, there is evidence for phonological syntax in the whales. Humpback song can more accurately be classified when sounds are segmented into subunits that are shorter than most individual utterances. Among killer whales each group has a group-distinctive set of calls, but each call may be made up of specific sequences of subunits, with some evidence that subunits are shared across populations that have no acoustic contact. This raises questions about whether learning these vocalizations requires formation of a new auditory template or whether the animal simply needs to remember a specific sequence of subunits that may be part of a species-specific repertoire. We do know that bottlenose dolphins can learn a new auditory template and produce vocalizations that match, because they can imitate the arbitrary frequency modulation pattern of a computer-generated tonal signal. This skill is used in the wild when dolphins learn to imitate the individually distinctive signature whistles of social partners. Several strands of evidence suggest that signature matching is used by one individual dolphin to address a specific partner within a group, and that the partner responds preferentially when its signature is imitated. Imitated signature whistles thus are learned signals that are used to label an individual where the association between individual and label is also learned. This kind of labeling with learned signals is important for human language but has seldom been described for animal communication systems. A focus on vocal learning among mammals thus helps bring a comparative focus on elements of language as diverse as phonological syntax and reference.
Period23 Sept 2017
Held atUniversity of Maryland, United States, Maryland
Degree of RecognitionInternational