Feeling calmer Cephas Picture Library / Alamy Stock Photo

Monkeys become more relaxed if they simply watch one monkey grooming another.

“If you walk down a street and see someone being nice to someone else, it gives you a warm feeling inside,” says Stuart Semple of the University of Roehampton in London, UK. It seems monkeys experience the same thing.

With his student Juliette Berthier, Semple studied 20 female Barbary macaques living in a semi-free ranging group in a Safari park-like environment in a UK forest.

When a macaque saw another being groomed, the observer started performing fewer “self-directed” behaviours such as scratching and yawning. These behaviours are thought to be signs of anxiety, so it seems the observer macaques became less anxious after seeing another macaque being groomed. “Merely watching grooming is in itself relaxing for monkeys,” says Semple.

The observer macaques also became more likely to participate in grooming themselves, either as groomer or groomee. Furthermore, they displayed more friendly behaviours in general, such as cuddling other macaques or feeding with them.

The phenomenon is similar to “emotional contagion”: humans become more cheerful if we meet someone cheerful, even online, and some parrots start playing when they hear other parrots making playful sounds. But in this case the effect lasted longer, in some cases 30 minutes.

The finding may help explain the phenomenon of “ASMR” (autonomous sensory meridian response). Some people experience a pleasant, calming tingle when watching videos of other people whispering or performing actions like tapping their fingers on surfaces.

“If you look at what sorts of behaviours tend to trigger ASMR in people, they’re basically grooming,” says Nick Davis of Manchester Metropolitan University in the UK. For instance, ASMR videos often include comforting gestures and gentle speech.

“The change in behaviour that we see in those animals seems to be similar to what we see in humans,” says Davis. “There’s a calming effect.” He wants to see studies of the physiological changes in the macaques, to see if they are similar to those seen in humans experiencing ASMR.

Semple agrees that there is an “interesting parallel” and speculates that videos in which one person is kind to another might also trigger ASMR.

For full article – Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2018.1964