Book Reviews - Review 394

Human beings are the only animals that make music, but something in our biological evolution must have laid the groundwork for our ability. Charles Darwin wrote, "The perception, if not the enjoyment, of musical cadences and of rhythm is probably common to all animals, and no doubt depends on the common physiological nature of their nervous systems." Was he right?

Henkjan Honing, a cognitive scientist in the field of musical perception, followed up Darwin's conjecture. Collaborating with academics in the field of biology, he spent several years investigating whether the rudiments of musicality are indeed evident in the behaviour of other creatures.

The question of which species to study, out of the thousands of candidates, was settled by two things: the relatively small set of animals available for study in captivity, and a scour of the Internet for videos of animals apparently demonstrating musical appreciation. Honing's curiosity was first sparked in 2007 by a video published on the Internet of a cockatoo named Snowball, dancing in rhythm to the pop tune "Everybody" by the Backstreet Boys. Snowball taps his feet, bangs his crested head and, at the end of the show, responds to the applause of his keepers with a sequence of energetic bows and squawks. It's hard, watching the video, not to believe that he knows what he's doing.

Honing recounts his work with other researchers investigating the musical perception of rhesus monkeys, chimpanzees, zebra finches, carp (? yes, carp), and sea lions. The essence of human musicality, Honing maintains, incorporates a sense of rhythm - the ability to perceive a continuous beat when music changes tempo - and relative pitch - the ability to recognise the same tune in different keys.

Monkeys and chimps, despite their genetic proximity to human beings, prove unable to respond to external rhythms (though chimps can beat in time without stimulus); zebra finches are very sensitive to timbre but barely to melody and rhythm; and carp can distinguish between classical music and blues. Yet as far as relative pitch is concerned, the perception of it appears to be a uniquely human talent; while the ability to move in time to a rhythm supplied from outside has been observed in just two types of animal: parrots (including cockatoos) and sea lions.

The fact that sea lions can move to a rhythm - indeed, at least one is known that does it even better than Snowball the cockatoo - appears to refute a hypothesis proposed by the American biologist Ani Patel that the capacity for rhythmic synchronisation is linked with the ability to create new vocal sounds. Patel suggested that both music and language were evolutionary developments of a more ancient trait of "musicality". The hypothesis sounds plausible, and Honing used it as the very thread of his researches; but he was forced to the conclusion that the neurological basis of musicality is more subtle than Patel imagined. He accepts this with a mixture of disappointment and excitement. On the one hand, we're further from understanding musicality than we thought we might be; on the other, there is so much more interesting research still to be done.

Aap Slaat Maat is an excellent read. Its subject is fascinating, Honing is an engaging writer, and he structures his material meticulously, in the form of pseudo-diary entries that jump about across the years so as to fit into a thematic story. As a learner of Dutch, I was pleased to find the first complete book I've read in the language so rewarding. I trust that readers will find it no less rewarding in the English translation that was published in 2019, so I recommend it to anyone interested in a relatively young field of research that, moreover, provides plentiful excuses to seek out funny animal videos on YouTube.