mise à jour du
29 mars 2009
The structure of primate social communication
Altmann SA
In Social communication among primates
Chicago University Press. 1967


Social communication among primates is a biological phenomenon and, like any other biological process, presents us with several major questions: (1) What is its structure? (2) How does it function? (3) What is its underlying causation? (4) How does it develop ontogenetically? (5) What is its adaptive significance? (6) How did it evolve? As with other biological processes descriptions of what we may call the "anatomy" or "structure" of communication are bound to be a primary focus of research attention during this early stage in work on primate behavior. Indeed, our ability adequately to answer the remaining questions will depend upon an understanding of the structure of communication. The special nature of such a structure lies in this: it is a structure not of objects but of events.
Addressed (Directed) Messages
Closely related to the distinctions between broadcast vs. narrow-band transmission and directional vs. nondirectional reception is the fact that some messages are directed toward particular individuals or groups, whereas others are to-whom-it-may-concern messages. Undirected, to-whom-it-may-concern messages do occur among primates, particularly in their predator-alarm calls and in their group-cohesion calls, both of which have been reported in many primates. However, most of the social signals of primates seem to consist of directed displays.
Messages may be directed in several ways. One way is to restrict the channel of transmission (for example, by using a quiet vocalization or a tactile message), so that the message is received only by certain individuals. Another is to use a private code or language known to some but not all of the recipients. A third way is to add to the message an ancillary component that indicates to whom the message is being directed.
Those components of a message that serve to direct it may be referred to as the address of the message. Note that addresses are, themselves, messages. They are communication about communication, that is, metacommunication (Bateson 1955). (Eavesdropping is the example par excellence of responding to messages that are directed toward someone else.) Itani (1963), in discussing Japanese macaque vocalizations that form his Group A, most of which are used in the coordination of group movements, writes, "few of them are directed at an individual. Some sounds are so low that they do not reach except a short distance, and others are loud and big enough to reach the whole troop. It is clear, however, judging from the manner and the line of gaze of the utterers, that generally they are not calling to a special individual."
Among primates-and doubtless among many other animals-facing and looking at the addressee is probably the most common means by which social messages are directed. (Doubtless, the efficiency of this technique is to some extent dependent upon the fact that for an animal with extensive binocular vision the position of the two eyes on the front of the face makes it fairly clear to other members of the group just who is being looked at.) Even when females present their hindquarters to a male, an act which in itself has conspicuous cues about who is the addressee, there is often visual contact or, at least, facing (Plate 17.2). Thus, one interpretation of avoiding visual contact-which has been described in rhesus (Altmann 1962a, Hinde and Roweil 1962), baboons (Hall 1962, DeVore 1962), bonnet macaques (Simonds 1965), gorillas (Schaller 1963)-is that it is a means of avoiding interactions. Not surprisingly, this behavior is usually given by the subordinate member of a pair, and its converse, direct staring, is usually a form of threat. Note that in such situations organs that are fundamentally receptors have come to subserve a transmitting function; according to Bateson and Jackson (1964), this is a common development in animal communication.
Particularly striking is the fact that messages may be directed toward the appropriate sense organ of the social partner. In our studies of baboons, this was not observed in vocal signals-which is not surprising, in view of crookedline transmission of sound waves (property 7). It was, however, conspicuous in many visual and olfactory displays (Plate 17.2). Adolescent males, at an age when they first began to make use of the mouth-gape or "yawn" as a threat were very poor at directing these displays (Plate 17.3). Gradually, however, they became more skilled at directing these displays toward the face, and hence eyes, of the females whom they harassed. This gradual perfecting of the technique of directing these displays may have developed out of repeated experience with the relative communicative impact of displays that varied in the extent to which they were directed toward the relevant sense organs.
This last case points up the fact that the directing components of a message may follow a different maturational pattern than the displays themselves. Jay (1962), describing the Indian langur, Presbytis entellus, writes, "in the late infant-1 stage the young langur produces the earliest recognizable forms of gestures and vocalizations which will be characteristic of its adult behavior.
Improved coordination makes it possible to direct movements towards objects and other monkeys . . . ."
In sothe cases, the presence or absence of addressing components may determine whether a particular display is communicative. Jay (1962) indicates that undirected grimaces, which are given by young langurs in play, are of no communicative significance, whereas directed grimaces outside of the play situation are. In baboons, directed mouth-gaping, or "yawning," is a powerful threat; in contrast, undirected yawns are of little or no communicative significance.
The directing or addressing component of a message may have a "pointing" function. When a monkey in an agonistic situation attempts to enlist aggression from a third party, and particularly when such a third party draws near (for example, when a female comes to the aid of one of her offspring), the monkey often gives agonistic displays toward the opponent with exaggerated addressing components, thereby singling out the adversary; we have observed this in rhesus macaques and savannah baboons. Itani (1963) indicates that Macaca fuscata may communicate the location of a concealed invader to the troop through "triangulation" of the directing components; an alarm call and various threat gestures are given repeatedly by a monkey from 5 to 15 m from the invader, and as the monkey continues his call incessantly, using trees and rocks as a shield, he jumps about, covering a half circle in which the invader is the center.
The concept of directed messages enables one to translate into verifiable form many statements about intent. For example, "The male intended to strike the female" might be reworded "The male directed his strike at the female (but missed)." In some cases, this may clarify the empirical basis for the impression that we know the subjective state of the organism.
A peculiar form of directed behavior has been observed in rhesus, bonnet, and Japanese macaques (Altmann 1962a, Simonds 1965, Itani 1963) and probably occurs in other primates as well. A behavior may be directed at nobody. This is not the same as undirected behavior. For example, a rhesus female sometimes will, while presenting to a male, direct a threat toward some fixed position that is not occupied by anybody. This seems to be a particularly strong stimulus to mounting. The behavior of a female in these situations appears to be indistinguishable from that in which she presents to a male while threatening an actual third party. Itani (1963) writes of the Japanese macaque:
An individual is attacked by a superior individual. He tries to direct the attack by uttering these sounds to a third individual nearby who has no connection with the trouble. When he finds no available third person about there, he utters these sounds toward an entirely false direction, that is, to an imaginary object, so that he can sometimes escape from his situation of being attacked.