When we feel stressed we often react in different ways like reaching for a slab of chocolate, pacing up and down or even scratching.
Stress is also felt by animals such as the macaques and is a biological response to physical and physiological challenges an animal faces in their environment. One particular response of stress in primates is scratching which is the repetitive raking of the skin on face and/or body, with the fingers of the hand or feet.
Humans scratch too when they are stressed.
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But does stress-induced scratching have a social function and can such stress behaviours be responded to by others?
Researchers from the University of Portsmouth conducted observational studies of 45 free-ranging rhesus macaques from a group of 200 on the 35-acre island of Cayo Santiago in Puerto Rico.
The research team monitored the social interaction between these primates for eight months.
They also monitored the production of scratching and social responses to scratching amongst the group.
The researchers found that scratching occurred in situations of great stress such as being close to a high-ranking individual or to non-friends.
The team also observed that when the macaques scratched, the subsequent reaction from others was less aggressive and more affiliative behaviour.
Stress scratching led to less likelihood of being attacked by other primates as stressed individuals can behave unpredictably or be weakened by their state of stress.
The likelihood of aggression when high-ranking primates approached a lower-ranking macaque with no scratching behaviour is 75 per cent while if scratching occurs then there is a 50 per cent chance of conflict.
The researchers found that scratching also reduced the chance of aggression between primates who did not share a strong social bond.
By letting others know about our stress through stressful behaviours such as scratching, they recognise the transparency in the situation and how we might react. This ultimately leads to the reduction of conflict which can benefit everyone involved.
Recognising stress in others is an important component of social behaviour and it seems that this leads to social cognition such as empathy for others.
Source: Scientific Reports
