Primate Behavior: Background

Most primates spend their lives in complex, tightly woven societies and need to frequently communicate with each other. They communicate with smells, sounds, visual messages, and touching. Non-human primates emphasize the use of body language. Human communication is far more focused on the use of oral sounds. Our speech is radically different from the hoots, howls, whistles, barks, slaps on the ground, and other sounds used by non-human primates to communicate. Our languages are complex symbolic systems. That is to say, our words are combinations of sounds to which we arbitrarily assign a specific meaning. Like all symbols, the meaning of words cannot be discerned by listening to the sounds. They must be explained. This is very different from a universally understood cry out from pain or fear.

Human language also has the characteristics of being both open and discrete. Openness refers to the ability to communicate about totally new things and ideas. In contrast, other primates almost exclusively communicate their present emotional mood and intentions. They are focused on the here and now. Discreteness refers to spoken words being individually distinct from others in the same phrase or sentence--they don't blend together. The oral sounds of some apes and monkeys are somewhat discrete at times as well. Unlike us, however, their communication does not involve displacement. That is, they apparently do not "talk" about things and events that are not here and now. People discuss such things as what the world was like two centuries ago. There is no evidence that non-human primates do this.

Can non-human primates learn and use human languages? Do they have the mental ability to comprehend a symbolic communication system and to use it creatively? Research with chimpanzees, bonobos, and gorillas to answer these questions has been ongoing since the 1960's. It is now clear that at least the great apes can learn and use a simplified version of the American Sign Language for the Deaf (ASL). However, it is not universally agreed that they can do so in an innovative way like adult humans. One of the stars in this research has been a male bonobo named Kanzi. Listen to the audio slide show linked below and make up your own mind about how well he uses language.

Odors, vocalizations, gestures, and facial expressions are used by non-human primates to inform others of their psychological state and present concerns, which is an important clue to what they are likely to do next. In the picture on the left, the outstretched hand and pleading facial expression directed toward another troop member are obvious indications of this chimpanzee's appeal for sharing. It also probably reflects and reinforces his or her lower position on the dominance hierarchy within the community.

Primatologists have observed that some communication patterns are commonly used by many primate species. These are discussed below.

Prosimians have excellent olfactory

sensing abilities. It is not surprising, therefore, that they usually use body odors to communicate. Adult male ring-tailed lemurs regularly mark their woodland territories with chemicals produced by scent glands in their wrists. This is similar to dogs, wolves, and cats marking their territories with urine. In both cases, the scent is recognized as a personal signature. Tamarins and marmosets also use scented urine to mark the gum trees that are important food sources in their territories. In all of these species, scent marking is a way of claiming territory and warning off intruders.

Most primate species, including humans, use threatening gestures, stares, and poses to intimidate others. Primatologists refer to this particular use of body language as agonistic displays

. Among non-human primates, they are usually sufficient to prevent physical fighting. In fact, physically violent encounters are rare among them. The dominant male in a monkey or ape community can usually prevent major conflicts and keep order by the use of often subtle agonistic displays. For instance, male baboons flash their eyelids. If this isn't sufficient, they open their mouths widely in a manner that looks like human yawning. Since the marmosets and tamarins cannot significantly change their facial expressions, their agonistic displays are different. Adult males chirp repeatedly and turn around to show their genitals from behind.

Most primate species communicate affection and reduce group tension by sitting close to each other, touching, and mutually grooming. The latter is referred to as allogrooming

in contrast to self or autogrooming

. Allogrooming is a powerful tool for communication. It is used by both monkeys and apes to reinforce male-female mate bonds as well as same sex friendship bonds. Chimpanzees often have ecstatic bouts of allogrooming that go on for hours when an old acquaintance rejoins the community. They also do it to calm emotions following wild, aggressive outbursts by angry adult males. Most members of the community also seem to very much enjoy grooming infants and may compete for the opportunity.

It is clear that allogrooming results in both social and psychological benefits for non-human primates. It often serves much the same purposes for humans, whether it be in the private setting of a family at home, where a parent might brush a child's hair, or in a public barbershop or salon. The experience of having someone run their fingers through your hair and massage your head in the process is usually physically pleasurable, and it generally provides a period of time removed from work or school concerns when relaxed, casual conversation occurs.

Among some species of primates, including humans, the urge to allogroom is so strong as to result in grooming animals of other species. Among non-human primates, inter-species allogrooming occurs when they are in captivity and deprived of the opportunity to groom their own kind. They are even known to groom people. However, it does not seem to be a pattern of wild non-human primates.


		A macaque and a human enjoy holding and grooming puppies (The dogs also enjoy it)

Petting a willing, appreciative dog has been shown in experiments to reduce the blood pressure of humans. This surprising psychological effect potentially has medical implications.


Chimpanzee begging gesture and facial expression