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Prosocial (Friendly) Interactions

Free ranging ostriches lined up behind soldiers

What is the function of an invitation display?

Invitation displays among group-living animals are ways of inviting friendly interaction. Long-necked birds such as ostriches commonly crane their necks upward and gather in a friendly group, as if engaging in a dance.

The photographer Marion Kaplan observed a group of ostriches apparently attracted by the upright rifles of marching soldiers (see

The event took place in Tsavo National Park in Kenya, in 1969. "A group of park rangers were practicing their drill as several ostriches, wild but used to human presence, wandered near by. Quite soon the ostriches, unherded and without encouragement, were in a tidy line behind the rangers. Their mood was curious, playful, imitative, not at all threatening" (Marion Kaplan, personal communication). Kaplan adds that the rangers enjoyed the ostriches, but higher authorities disapproved, so ultimately the two groups were separated.

How do dogs and cats typically react to contact with the vulnerable underbelly area?

Grooming is a common prosocial activity, so group-living animals commonly use a posture suitable for grooming as an invitation display. Dogs sometimes like to be scratched on their bellies, so they convert the universal canine submission posture (lying on the back) into an invitation display. They expect to be scratched by a friendly human in this position, particularly if they have a history of belly rubs.

Cats also use the lying on the back posture to indicate peaceful intentions, but (with rare exceptions) they do not use it as an invitation display. For cats, it is appeasement gesture, showing trust and affection but not inviting contact. Therefore, cats normally do not like a human touching their underbelly fur. When they are putting on a submission display to a human by rolling over on their backs, they do not want to be touched. People who own dogs sometimes misinterpret a cat's display as an invitation posture. Thinking the cat wants to be scratched, they reach down to scratch the cat. To most cats, that is unexpected, and it is a violation! The cat bites or scratches or flees.

A dog may lie on its back as an invitation display to invite grooming by a human. Cats use the same display only as a submission posture and may react badly to contact with their soft, exposed underbelly fur.

What is a typical pattern of mutual grooming, in monkeys?

Monkeys solicit grooming from other monkeys by presenting their backs. If the other monkey is interested in a grooming session, it will pick through the presenting monkey's back fur, removing dirt or insects. After a while the grooming monkey will turn and display its back to the other, which will groom it in turn.

Pandora grooms Virgil (photograph: Barbara Smuts, used by permission)

Psychologist Barbara Smuts (1986) spent three years living with baboons to study their prosocial behavior. The picture shows "Pandora" grooming "Virgil." You can see Virgil's unmistakably blissful expression. In this case, Virgil's belly fur was being groomed.

Smuts used the technique of habituation. Smuts spent every day with the baboon troop but refused to interact with them. Eventually the baboons simply ignored her and went about their business.

How did Smuts interact, or not interact, with the baboons?

Smuts documented many examples of friendly or prosocial behaviors. She found that long-term friendships and alliances often extended to different age groups, such as parents and children. The blissful scene of Virgil and Pandora in the preceding photograph was soon transformed into a scene of play.

After a few moments they were joined by two of Pandora's offspring... Pyrrha was in a rambunctious mood, and she used Virgil's stomach as a trampoline, bouncing up and down with the voiceless laughter that accompanies baboon play. Every now and then Virgil opened his half-shut eyes, and, gently touching her with his index finger, he grunted as if to reassure her that he did not mind the rhythmic impact of her slight body against his full stomach. (Smuts, 1986, p.4)

Despite her procedure of refusing to interact with the baboons, Smuts became accepted by them as if she was a friend. "Once I fell asleep surrounded by 100 munching baboons only to awaken half an hour later, alone, except for an adolescent male who had chosen to nap by my side. We blinked at one another in the light of the noonday sun and then casually sauntered several miles back to the rest of the troop, with him leading the way" ((Quoted at this URL:

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