Rhesus Monkeys Lack Ability to Detect Beat in Music

A new study reveals rhesus monkeys cannot identify beats in a varying rhythm, suggesting that the ability of beat detection is unique to humans and is absent in nonhuman primates.

A team of researchers from the University of Amsterdam (UvA), Netherlands, and the National Autonomous University of Mexico (UNAM), carried out experiments with rhesus monkeys to find if they can detect a beat in music.

They used the same stimuli and experimental paradigms that were used in previous studies conducted on humans and babies. Such studies have already shown evidence that humans can detect beats in music. Even newborn babies can pick up the beat from music, suggesting that beat detection is an inborn behavior and not something to be learned.

For their new study on rhesus monkeys, the research team led by Henkjan Honing, professor of Music Cognition at the UvA, measured brain signals using electrodes while the participants were listening to music. They found that the rhesus monkeys were able to detect the rhythmic groups in music, but they could not perceive the beat from a varying rhythm.

The results support the vocal learning hypotheses which suggest that the species possessing the ability to mimic sounds are able to detect music. They include humans and some species of birds. But the knack to mimic sounds is either weakly developed or entirely absent in nonhuman primates.

"These findings are in support of the hypothesis that beat induction (the cognitive mechanism that supports the perception of a regular pulse from a varying rhythm) is species-specific and absent in nonhuman primates," the researchers wrote in the paper.

"In addition, the findings support the auditory timing dissociation hypothesis, with rhesus monkeys being sensitive to rhythmic grouping (detecting the start of a rhythmic group), but not to the induced beat (detecting a regularity from a varying rhythm)," they said.

The findings of the study, "Rhesus monkeys (Macaca mulatta) detect rhythmic groups in music, but not the beat", are published in the scientific journal PLOS ONE.