Speaking of animals and dissonance, an upcoming article in the journal Primates investigates the question of whether our closest living relative, the chimp, shows a preference for consonant over dissonant music. The answer is yes, suggesting that the human preference for consonant music lies in our genes. But be aware that this result is based on just a single chimp.
Background: Humans prefer consonant over dissonant music, as consonance “evokes a pleasant feeling.” The fact that the human preference is seen in infants as young as two days old suggests that this preference is inborn rather than learned. Animals as distantly related as birds can distinguish between the two types of music, but studies of another primate, the cotton-top tamarin (Saguinus oedipus) showed no preference for consonance. The authors of this study looked at a closer relative to see if perhaps the trait “preference for consonance” might not only be genetically based, but also have appeared in the primate lineage more recently.
Methods and materials: The authors studied, over six weeks, a single five-month-old female chimpanzee (Pan troglodytes) named Sakura. She had been reared in a zoo by humans, as her mother had rejected her. The authors claim that she had never been “exposed to any particular music source such as a radio, TV, or CD player throughout her development. . ”
Sakura was strapped onto a bed with a soft belt, and was forced to listen to either consonant or dissonant music. There were six sets of computer-generated music, each set consisting of a consonant piece and a nearly-identical dissonant piece, in which some of the notes had been swapped for dissonant ones (see paper for further details). A string was attached to her right arm (see Fig. 1), and by pulling this string she could affect whether the music stayed the same or changed to the alternative version (i.e., consonant to dissonant or vice versa). The recorded music began. If the chimp pulled the string within seven seconds, the same music would continue playing for up to two minutes. If she pulled the string between 7 and 14 seconds, the music would also continue, but with a pause of a few seconds. If she waited longer than 14 seconds to pull the string, the music would change to the alternative version. Sakura was tested once per week for the six week period.
Fig. 1. Sakura in bed, choosing the music that appeals (from original paper).
Results: The mean duration of consonant music sessions for Sakura was 24.6 seconds, but only 15.9 seconds for the dissonant music. Statistical analysis of the sessions (each including about 10 bouts of each type of music) showed that this difference was significant. That is, there was a significant preference for the consonant tunes over their dissonant alternatives. When Schoenberg was played, Sakura became very agitated and flung feces at the observers (kidding!)
What it means: The authors interpret this result as suggesting that “one of the major factors that constitute musical appreciation might not be unique to humans; instead it might be something that we share with our phylogenetically closest relatives.” That is, dissonant tones may affect the nervous systems of chimps and humans in similar ways, and lead to similar subjective sensations. That seems to be a reasonable conclusion, although of course we need studies where the number of primates exceeds one.
The authors note one potential flaw in the work: suppose that the dissonant music caused the chimp to relax more. Then she would be less inclined to pull the string when that music was playing, and according to the experimental protocol the music would then change over to the consonant form. This could give the impression that she preferred the consonant over dissonant music as a simple experimental artifact. The authors say that they consider this possibility “unlikely,” but they didn’t control for it. One way would be to change the experimental protocol in a separate experiment so that the music would change over when the string was pulled quickly rather than after a longer interval.
One question the authors don’t bring up is whether animals of any sort produce consonant rather than dissonant music. Do birds, for example, tend to sing consonantly rather than dissonantly? I am a music tyro and don’t know the answer. However, the efficacy of animal communication may rest on things other than whether it’s pleasant for them to hear.
T. Sugimoto, H. Kobayashi, N. Nobuyoshi, Y. Kiriyama, H. Takeshita, T. Nakamura, and K. Hashiya. 2009. Preference for consonant music over dissonant music by an infant chimpanzee. Primates, in press.