Marc D. Hauser

Abstract

In this chapter I review work on the mechanisms underlying primate vocal

communication, focusing in particular on my field studies of rhesus monkeys.

By understanding the neurocognitive substrates of animal vocal signals we will

be in a stronger position to evaluate the roots of our musical sense. Primate

vocalizations use different acoustic parameters to convey information about

their emotional states as well as about objects and events in their environment.

Nonhuman primates have the capacity to produce vocalizations that evidence

some of the rudimentary properties of our system of reference. Furthermore,

some of these vocalizations play a role in a system of conventions, crucially

related to the maintenance of social relationships within a group. A certain

amount is currently known about hemispheric asymmetries underlying the pro-

duction and perception of species-typical vocal signals. Contrary to earlier claims,

nonhuman primates show significant asymmetries, paralleling some findings in

humans. Specifically, the left hemisphere plays a dominant role in the perception

of conspecific vocalizations, and during production of functionally referential

signals.

I can remember the first time I heard Elizabeth Schwarzkopf singing

Wagner. Not only was I moved emotionally, but I was astounded by the

clarity with which her words resonated, carried by one of Wagner’s many

memorable themes. But an equally memorable acoustic moment hap-

pened just a few minutes later. When I stepped outside the opera house,

a newborn was looking up at its mother, cooing and gurgling, compos-

ing its own music; and next to the mother and child sat an obedient dog

that occasionally let out a contented moan. Other melodies, other voices.

Music certainly can be the voice of the heart, and it can also be the mes-

senger of meaning for human adults, human infants, and all animals.

In thinking about the melodic utterances of animals, we can ask several

comparative questions that may help us understand the origins of our

own species’ musical capacity—our musical sense. To avoid confusion,

however, we must be careful to distinguish questions of underlying mech-

anism (e.g., developmental change, neurophysiological substrates) from

those of evolutionary function (i.e., adaptive significance) and history

(i.e., phylogeny). Thus, we might ask, when birds, whales, gibbons, and

humans sing, are the same neural and hormonal systems recruited? This

is a mechanistic question, one centered on proximate causation. Another

question, focusing on a different set of causal issues, is, when birds,

whales, gibbons and humans sing, does their performance influence

reproductive fitness? does it contribute to the propagation of genes into

subsequent generations? This is a question about ultimate causation. By

understanding both kinds of problems, we will be in a better position to

evaluate the design features and evolutionary history of musical systems.

6

The Sound and the Fury: Primate Vocalizations as Reflections

of Emotion and Thought