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10 February 2017

Monkeys and dogs judge humans by how they treat others

Dog being petted
Dogs have evolved to be extremely sensitive to our behaviour




Comparative psychologist James Anderson at Kyoto University and his colleagues wondered whether other species make social evaluations in a similar way.


They began by testing whether capuchin monkeys would show a preference for people who help others. The capuchins watched an actor struggle to open a container with a toy inside.

Then this actor presented the container to a second actor, who would either help or refuse to assist. Afterwards, both actors offered each capuchin food, and the monkey chose which offer to accept.

When the companion was helpful, the monkey showed no preference between accepting the reward from the struggler or the helper. But when the companion refused to help, the monkey more often took food from the struggler.

Playing ball

The team also investigated capuchins’ attitude to fairness. In this test, two actors began with three balls each. Actor A requested balls from actor B, who handed over three balls.

Then actor B requested balls from A, and A either gave three balls back or no balls. Lastly, both actors offered the monkeys a reward as before.

The monkeys had no preference when actor A gave back three balls, but chose actor B more often when A had not returned the balls.

Finally, the researchers tested whether dogs preferred people who helped their owner. Each owner tried to open a container then presented it to one of two actors.

This actor either helped or refused to do so, while the other actor was passive. Then the two actors offered the dog a reward and it chose between them.

The dogs had no preference when the first actor had helped their owner, but were more likely to choose the passive actor if the first one had refused to help.

Emotional response

Anderson thinks the results show that monkeys and dogs make social evaluations in a somewhat similar way to human infants. “If somebody is behaving antisocially, they probably end up with some sort of emotional reaction to it,” he says.

Monkeys in the wild are likely to use similar processes to decide which members of their group they can cooperate with, says primatologist Frans de Waal of Emory University, Georgia, who has written about the origins of morality.

“Chances are that if these animals can detect cooperative tendencies in human actors, they also can in their fellow primates,” he says.

Dogs’ long relationship with humans means they’ve evolved to be extremely sensitive to our behaviour – not just to the dog, but also to other humans.





Journal reference: Neuroscience & Biobehavioral Reviews, DOI: 10.1016/j.neubiorev.2017.01.003

Read more: Bonobos know when others are being treated unfairly – and react; Tracing the roots of human morality in animals; A Natural History of Human Morality: Why being good is a miracle

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