Non-human primates do not generally respond to music; they rather prefer silence. But researchers found that cotton-top tamarin (Saguius oedipus), a rare South American monkey, though immune to human music, did respond to music.

In fact, much like humans, they displayed many kinds of emotions on hearing the music. Only that the music played was not the ones humans generally listen to but were compositions that contained elements of monkey calls.

Psychologists have long tired, in vain, to trace the evolutionary roots of these responses to music in non-human primates. This study is among the first to show that non-human primates can truly appreciate music.

Musician David Teie of the University of Maryland had recorded the monkey calls that conveyed two opposite emotions — threats and/or fear, and affiliation, a friendly, safe and happy condition.

In a paper published in the journal Biology Letters, Dr.Charles Snowdon, professor of psychology at the University of Wisconsin-Madison and Dr. Teie reported that the monkeys could tell the difference when different compositions that contained elements of monkeys calls were played for five minutes.

For instance, after hearing fear music, the monkeys displayed more symptoms of anxiety and increased their movement. In contrast, monkeys that heard "affiliative" music reduced their movements and increased their feeding behavior — both signs of a calming effect.

The study became possible as Dr. Teie, who plays the cello in the National Symphony Orchestra, could easily differentiate and identify the emotions conveyed when he heard recordings of monkey calls.

According to Dr. Snowdon, Dr. Teie went to the next level of actually composing the music using specific features he noticed in the monkeys' calls. The specific feature of the recordings was that it had rising or falling pitches, and the duration of various sounds.

Several studies show that babies who are too young to understand words can still understand the emotion conveyed in pitches: a long tone and a descending pitch has a soothing effect, and a short tone has inhibiting effect.

According to Dr. Snowdon, a long time researcher into primate behaviour, legato (long tones) are used to calm babies and a staccato to make them stop doing something. Approval has a rising tone, and soothing has a decreasing tone. Any parent would know the effect of a “no” when expressed to a baby in a short and staccato tone. Lullaby always has a slow, soft and long pitch.

Monkeys interpret rising and falling tones differently than humans. Monkeys actually showed a calming effect on hearing heavy-metal music.

For cotton-top tamarins, communication is much more than just information, notes a release from the University of Wisconsin-Madison. “I am not calling just to let you know how I am feeling, but my call can also stimulate a similar state in you,” Dr. Snowdon says. “That would be valuable if a group was threatened; in that situation, you don't want everybody being calm, you want them alert. We do the same thing when we try to calm a baby. I am not just communicating about how I am feeling. I am using the way I communicate to induce a similar state in the baby.”

The similarities in communications between monkeys and people suggest deep evolutionary roots for the musical elements of speech. “The emotional components of music and animal calls might be very similar, and from an evolutionary perspective, we are finding that the note patterns, dissonance and timing are important for communicating affective states in both animals and people,” he says.

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