Vocal Learning and Auditory-Vocal Feedback

Vocal learning is usually studied in songbirds and humans, species that
can form auditory templates by listening to acoustic models and then learn
to vocalize to match the template. Most other species are thought to develop vocalizations without auditory feedback. However, auditory input
influences the acoustic structure of vocalizations in a broad distribution of
birds and mammals. Vocalizations are dened here as sounds generated
by forcing air past vibrating membranes. A vocal motor program may
generate vocalizations such as crying or laughter, but auditory feedback
may be required for matching precise acoustic features of vocalizations.
This chapter discriminates limited vocal learning, which uses auditory input to fine-tune acoustic features of an inherited auditory template, from
complex vocal learning, in which novel sounds are learned by matching a
learned auditory template. Two or three songbird taxa and four or ve
mammalian taxa are known for complex vocal learning. A broader range
of mammals converge in the acoustic structure of vocalizations when in
socially interacting groups, which qualifies as limited vocal learning. All
birds and mammals tested use auditory-vocal feedback to adjust their
vocalizations to compensate for the effects of noise, and many species
modulate their signals as the costs and benefits of communicating vary.
This chapter asks whether some auditory-vocal feedback may have provided neural substrates for the evolution of vocal learning. Progress will
require more precise definitions of different forms of vocal learning, broad
comparative review of their presence and absence, and behavioral and
neurobiological investigations into the mechanisms underlying the skills.