Until recently, nonhuman primates were thought to prefer silence over music based on research with, e. ., New World monkeys such as cotton-top tamarins and marmosets. In several studies the monkeys' living space was enriched with differend kinds of music. However, they preferred the areas with silence over these with music or other types of sound: a repertoire ranging from techno to Mozart and German lullaby’s. Mozart was disliked most.

The study from Emory University that came out last week used a selection of African, Indian and Japanese music to see whether chimpanzees would prefer any of these musical styles. A sample of each style was presented for forty minutes for eight days in different sections of their normal habitat. The question was: would they prefer to hang out in any of these areas? Or would they choose the quieter or silent areas?

The study reports that the Chimpanzees stayed significantly longer in areas where African or Indian music was played, and avoided those with Japanese music or silence. Conclusion of the researchers: Chimpanzees prefer some musical styles over others, suggesting it was the regular rhythm of the Japanese music that put them off. They write in a press release from APA:

“Chimpanzees may perceive the strong, predictable rhythmic patterns as threatening, as chimpanzee dominance displays commonly incorporate repeated rhythmic sounds such as stomping, clapping and banging objects”

Sounds reasonable, not?

Well, the experiment was not designed such that it could show that it is indeed the rhythmic structure that these chimps were attending to. In fact, there is no convincing evidence as yet that chimpanzees, or any other nonhuman primate, can actually perceive rhythmic regularity (see earlier entry).

Although it is suggested that apes (as opposed to monkeys) might have some of the neural circuitry that is needed for beat perception (Merchant & Honing, 2014), it has never been shown that any of the great apes can perceive the beat in a rhythmically varying stimulus such as music.

What has been shown, however, is that monkeys can be sensitive to the rhythm structure or rhythmic grouping. Hence it is more likely that it is the rhythmic structure (or rhythmic grouping) that the chimpanzees use to distinguish between the musical fragments, instead of the perceived regularity: the beat. Nevertheless, it could also be any of those many other features of music that makes the difference for them: dynamic contour, timbre, note density, melodic contour, timing, etc, etc.

Mingle, M., Eppley, T., Campbell, M., Hall, K., Horner, V., & de Waal, F. (2014). Chimpanzees Prefer African and Indian Music Over Silence. Journal of Experimental Psychology: Animal Learning and Cognition. DOI: 10.1037/xan0000032

Merchant, H., & Honing, H. (2014). Are non-human primates capable of rhythmic ? Evidence for the gradual audiomotor evolution hypothesis. Frontiers in , 7 (274) 1-8. DOI: 10.3389/fnins.2013.00274.