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Humans must realize that much of their communication would seem highly impoverished to many animals. Telephone talk, computer messages or the written word only provide one channel whether auditory or visual to express the nuances of the message. Mind you, language is a very complex system and in addition to its arbitrary nature, complexities of temporal referent and fine details of labelling, we also have a major aspect of social relativity expressed by word use, dialect, accent, jargon, pitch, inflection and a host of other prosodic features which allow us to comprehend more than the actual words coming over the phone.
In many cases, however, humans do not realize the wealth of information they are processing, storing and responding to. This was emphasized by Ned Hall's early book, "The Silent Language" which discussed the messages sent by cultural behaviour which in many cases totally contradicted the overt spoken word. In 'The Hidden Dimension' Hall focused on the use of space as a cultural reality which transmits messages about perception of self, others, social situations, dominance and a host of other features. Most monkeys wouldn't have to read Hall's book. They know that space is a very important message field, not just a metaphor for all kinds of information. Humans have become more and more aware of subtle features such as angle of gaze, position in a room and nature of clothing, in the self projections that they are attempting to create. However, our increasing manipulations at the level of marketing, rank establishment and diplomacy have only recently been coupled with an increasing awareness that this subtlety is based on a foundation arising from our primate past.
Thus a brief history of how communication has been studied in primates seems in order. Monkeys did not have much value to science other than as curiosities and pets until Darwin's theorizing led people to think that they could learn something about humans by studying them. Even in the late 1800's very few apes or monkeys lived long in captivity. Darwin was an early exponent of using the comparative method to study communication systems in his 'The Expression of Emotions in Man and Animals'. Other researchers became fascinated with the possibility that they could learn about humans this way and proceeded to try to study primate both in captivity and the wild in the 1890's. Garner reported that he had been able to interpret some sounds of monkeys as having specific meanings and in particular that they had a word for 'death'. Of course, later research denys any such specificity to primate vocalizations.
In the years that followed considerable emphasis was placed on investigating vocal communication. It was difficult before the advent of reliable sound recording equipment but efforts were made to count up the number of different types of vocalizations made by a variety of species. Also efforts were made to teach a young orangutan and a young chimpanzee to talk, but these had very minimal success. Although the animals seemed to make a great effort to vocalize when requested, the shape of their lips, tongue, pharynx and nasal cavity made the shaping of sound very difficult for them. Probably the most famous of these 'talking apes' was Vicki a young chimpanzee who was raised and trained in a human family in the 1950's. She obviously understood about 90 to 100 English phrases but could only produce four somewhat distinguishable words, Mama, papa, cup and up. Eventually, the effort to study human verbal language in apes was replaced by efforts to find modalities in which they might show more success as we will discuss in lecture #6.
Meanwhile sound spectrographic analysis of primate calls began in the late 1950's as recording equipment improved, and analysis of vocalizations based on pitch, frequency, band-width and pattern began to reveal some level of systemization in primate calls. Early work by Rowell and Hinde at Cambridge led to the idea of a call cycle; they grading of one call unto another as various aspects of call structure were modified. This tied in with a widely held idea that primate calls were governed by emotional responses to situations. They were seen as hard wired expressions of pain, fear, rage and maternal solicitude, which were governed by genetic background and were evident from infancy. Separation experiments were done to see if infants would possess a species specific repertoire in the absence of learning or exposure to their species. The results of the type of experiments were totally confounded by the major trauma that isolation rearing presents to primates. Infants did produce calls, but they did not use or comprehend them in social contexts at all. These youngsters behaved in totally inappropriate ways and did not act or respond as if what came out of their mouths had any meaning. It is worth noting that their facial gestures and proxemic kinesic behaviour were also highly inappropriate for the social situation they were in. This is not to say that some vocalization in primates are not hard wired, because it is clear in a variety of species such as mouse lemur, galago, squirrel monkeys etc. that infant vocalizations occur and are responded to appropriately by adults. Infant lost calls, nursing requests, and screams of pain will bring appropriate response and are clearly communicative. However, there is a lot more to primate vocal systems than these kinds of calls. As more and more research has been conducted on vocalization, the complexity of the system is slowly being unravelled. In 1967 Struhsaker first published data suggesting that vervet monkeys could label predator danger as being from the air 'eagle alarm', the ground 'leopard alarm' or from snakes 'snake alarm'. In the late 1970's this work was picked up and spread to a wide variety of forms and now we know that many prosimians and new world monkeys have variable predator alarms. The work with vervets was expanded to demonstrate a greater complexity of alarm calls, to demonstrate that they had to be learned by the young, that they would operate in the absence of a real predator (by using tape recording) and that they had an individual component. Other studies revealed differential use of other vocalizations such as 'grunts' and 'coos' which could only be discriminated by sound spectrographic analysis but which had clearly different meanings for the animals using them. The vervet work and some research on marmosets and mouse lemurs also suggests individual recognition of calls. In other words, the sounds not only convey a message, but also information about who sent it. This may include aspects of kin line, rank, and group membership.
As you can see, a lot of effort has been expended on studying vocal communication. Visual, olfactory and tactile systems have only recently been receiving the same kind of emphasis. Part of the reason for this is the difficulties of recording the material. Unless the animals are in a fairly small enclosure or cage it would be very difficult to record them all, even on a widescan video, because in any kind of naturalistic habitat they can be at a variety of levels, facing the other way, or out of sight behind a bush. If you want to get data on a natural intact social group living in its own habitat and dealing with predators, conspecifics, in migrations, socialization patterns, etc, you cannot get much in a small cage environment, unless you are dealing with very small animals, such as in marmosets or some prosimians. However efforts to circumvent these limitations have been made and more and more data is becoming available. Use of picture recognition of facial gestures is a common technique in laboratory situations and does suggest recognition of and individuals and information. Video driven testing situation suggest that information can be sent via facial gestures from one animal to another so they can co-operate to solve problems. Postural analysis, approach techniques and social grooming are analysed for the communicative content on social relations that they reveal. These are areas I wish to focus on in later lectures.
In order to discuss these codes of communication with intelligibility, I will spend the rest of this lecture reviewing the channels and modalities of communication commonly used by primates. Those who are already conversant with these I would suggest go and read Edward Hall's books 'The Silent Language' and 'The Hidden Dimension' if you are not already familiar with them, as background materials for upcoming lectures.
Since primates do not leave written work for generations yet to come, an animal who has information to transmit must provide it within the sensory range of another who can decipher the code. Some of these messages are intentional and some are not. I must pause here to comment that the term 'intentional' is subject to some controversy but animals do have choices about acting and responding and it is at this level that I am using the term. A monkey can choose to approach or avoid another, to groom or not to groom, to stay or leave when an approach is made or to vocalize or not, at least in some situations. In other aspects they do not have a choice. They cannot change what species or age or gender that they are . In terms of cues they cannot change what they look like, who they were born to, what they smell like or characteristics of their voice. And it is true that some calls that appear in newborns are only modified by the maturation of the vocal tract. Therefore, in order to sort out differences between these two situation I tend to borrow from G.G. Simpson's view of behaviour which he saw as having a boundary at the level of the individual. Those things which occur within the individual, and over which the individual has no control I call basic types of communication. This includes information that any other member of the species (or another species) can acquire just by being in the presence of the animal. The examples of species, age, gender, health, individual identity, etc. would be included here. The other level of communication I would characterize as "Interactive", where there is an active relationship of information transfer between two or more animals whether or not they are in sight of one another. Clearly the interaction could continue in the auditory channel, with out of sight animals such as long calls given by a variety of primates both to advertise their presence and to attract mates. Just as clearly this would also include scent and urine marks left to mark territory or advertise sexual state.
Both these levels of communication utilize the four main channels of sensory input open to primates. These are the Visual, Auditory Tactile and Olfactory/Gustatory channels. Within each of these are a number of coding modalities or ways of patterning behaviour which transmit information in a form which can be deciphered by a receiver who is familiar with they system. To begin with the basic level, the visual channel allows visual perception of the sender. The receiver gets information on size, colour, proportions, gender, movement patterns, proximity to others and can assemble this input into a judgement on species, age, gender etc. Among some species detailed aspects of facial colouration would be important recognition markers (such as among guenons which are a group of 12 to 15 species of African mainly arboreal monkeys of similar size who are most notably discriminated on the basis of face colour patterns). Recognition of species and gender may also rest on the presence of a mane, (hamadryas baboon) sexually dimorphic body colour and size, length of canine teeth and other more obvious sexual characteristics. If the observer is also a member of the same group, recognition of the individual and therefore of its rank and matriline relationship (if any) is also implied. The sender can do nothing to alter this, just as she cannot alter physical manifestations of estrus such as swelling or pheromones. Pheromones are recognized via the olfactory channel. Primates are very nosy and will sniff and lick to acquire information if they can get within proximity. Sometimes they will touch another and sniff their fingers. States of sexual receptivity are often indicated by olfactory cues but how both the sender and receiver respond to such information can be quite variable and is at the interactive level. State of health can also be revealed by olfaction because many sick or stressed animals produce toxic byproducts or don't' digest their food well, with resulting smells. Urination and defecation also leaves olfactory information and one clear communicative use of that is the habit chimpanzees have, when they are on boundary patrol searching the edge of their range, of sniffing any chimpanzee feces they find. If it is feces from a stranger they become very quiet and search visually. If they find a strange chimpanzee in their range they will usually attack it violently. The sender of such a message has no intent to provide information but its message is interpreted by the recipients.
The auditory channel can also provide information at the basic level. Most people only consider the vocal modality of sending, but footsteps, branch noise and falling fruit can also provide information about location and potential resources which may not be intentionally sent. Vocalizations may also occur due to fear or rage which may be uncontrolled Humans who hit their thumbs with a hammer or see a major diaster may have a similar uncontrolled outburst of vocalization (in fact, Bickerton and others have argued that humans have two sets of language abilities, a protolanguage, which is not very complex and can be elicited by very basic motivators and our more complex learned language systems). The tactile channel is a very interesting one for humans to consider. In many western sub-cultures touching others is bound up with a wealth of social/emotional/sexual freight. Most non-human higher primates spend a lot of time and energy grooming each other, soliciting grooming from others, sitting in contact, sleeping in clumps and generally touching each other. Usually who one sits with, grooms with, sleeps with etc. says a great deal about one's social relations or position. But there is a little (if any) evidence to suggest that such activity is done "in order to demonstrate" that one has social/physical access to another. Instead, it occurs for the intrinsic benefits, comfort and support that occur to primates from such social tactile contact. A major exception to this would be consort behaviour in which the close proximity, grooming and sexual behaviour indicate a particular relationship and may be intended to intimidate others from approaching a potential mate. Thus all four sensory channels allow the transfer of information at a basic level. Other animals are involved as receivers, but in many cases the communication is not an interaction.
Interactive messages are also sent in these four channels but here I will focus on brief discussion of the various modalities through which the information can be coded. Beginning with the visual channel we have the modalities of face, hand and body gestures, kinesics, proxemics and visual displays. I will be discussing these in more detail in the next lecture, but will outline their importance briefly here. As a general statement I would say that a very large proportion of information transmitted by social primates is through the visual channel. Facial gestures can be quite overt, but in the main they are very subtle glances, look away, movements of ears, eyelids and mouth corners. Piloerection, or erection of the fur, is usually perceived visually unless two animals are in contact. Kinesic behaviour or movements of the body can transmit emotion or intention. Tense, cowering, trembling unsteady movement can send one kind of message, while confident swaggering, tail held high, head high, relaxed sprawl or assured approach to resources sends quite another. Young animals watch all of these behaviours and positions, often trying out various posture in play. Proxemics refers to use of space and proximity to other animals. In a newly observed group familial relations can often be assessed by observing duration, frequency, and closeness of association. Use of the physical space also provides information about degree of integration into the group and access to the resources. Male baboons who sit on the edge of the group may be watching out for predators, but may also be strangers slowly attempting to work their way in. A choice between these interpretations would rest on factors such as their orientation (which way they were looking) nervousness, closeness of others and their behaviour before and after this observation etc. Visual displays such as the vervets 'red white and blue' genital intimidation display or branch shaking by baboons and macaques are series of clear ritualized movements which are used to send an unambiguous message. Who will send these, where and when, are matters of decision, but once the display has begun it usually follows a fairly uniform course.
Interactional communication in the auditory channel frequently involves vocalization as the modality. Primate species have a characteristic repertoire of vocalizations which range in number from about 10 to 40 or so different vocal signals. They are referred to by a wide variety of English terms such as 'bark', 'grunt', 'trill', 'chirp', 'whistle', 'waabark', 'hoot', etc. but it is very difficulty to get an idea of what they sound like without actually hearing them. As mentioned above, some vocalizations such as vervet 'grunts' may sound indistinguishable to humans and yet occur in quite different contexts with different outcomes, and can be differentiated by sound spectrographic analysis. Elke Zimmerman has conducted research on Mouse lemur 'trills' which suggest individual differences and population specific 'dialects' which may influence breeding patterns in this species. Our understanding of the level of individual discrimination and specificity of meaning for primate vocalizations is continually increasing. Non vocal auditory input also occurs from hand slaps to the ground in threat, to branch shaking which can occur in the context of territorial marking or defence.
Active olfactory communication occurs in a range of contexts which are influenced by the taxonomic level of the primates involved. Many prosimians are nocturnal and some are solitary or only semi-social. Thus much of their communication is through the olfactory channel because they are small, alone and in the dark. Extensive vocalizations could be dangerous due to predation by owls and other nocturnal hunters. Most of these prosimians have specialized scent producing apocrine glands on their chests, wrists, shoulders, throats or ano-genital regions which they rub on tree trunks or branches. These relatively long term marks provide information on gender, individual, and sexual state which can be acquired by the next visitor. Over marking is frequent especially in a sexual context or at territorial boundaries. There is some idea that pathways through branches are also marked which helps animals avoid getting caught in a 'cul de sac'. New World monkeys also mark quite extensively, both with scent glands and by urine washing. They rub urine on themselves, each other and the sub-substrate. This may help establish a 'group smell' or make animals more relaxed with each one another. State of estrus in higher primates are often accompanied by olfactory cues which may encourage males to approach and stimulate them to mount. Many experiments have been done with ovariectomized female monkeys to see whether visual or olfactory cues are more potent in eliciting male response. In some cases males do not respond immediately and the females must engage in proceptive behaviour in which she attempts to solicit male attention, often by presenting her hindquarters right to the male's face. Primates also use olfactory cues to test fruit and an obvious negative response by one to a fruit source may mean that others will leave it alone.
The tactile channel fulfils a wide variety of functions in addition to communication. Nonetheless a grooming interaction can have a calming effect on anxious animals and contact for reassurance after an agonistic episode is very common. Begging for food or contact frequently occurs in chimpanzees, where one animal reaches on to another and gently touches the others' face or body with the back of their hand. Infants reach out to strangers to make contact while still clinging to their mothers with their other hand. As they become more confident they can let go and approach the other. These are some of the tactile situations which provide information about the state, motivations and intentions of an actor that can be decoded by the receiver of such a message.
These four channels are also used by humans but with a rather different focus. Most of us use the auditory/vocal channel as our main interactive mechanism, with some backup from the visual. Many western people make every effort to ignore the olfactory channel or cover it up, even though experimental work shows that we still have acute olfactory perceptions. Other cultures are more aware of olfactory information transfer and may value it quite differently. The same can be said for the tactile channel especially outside the sphere of sex and courtship. Obviously tactile interaction is necessary for sex, but the symbolism this represents makes other areas of tactile contact difficult to permit in some cultures. There are many societies in which men have tactile interactions with other men, -sitting, holding, tattooing, grooming etc. and women with women but few with unrestricted touching between the sexes. Primates are much more relaxed about his, possibly because they use sex for so many different social purposes besides reproduction. This is a general statement of course, but it will serve as a good place to end this lecture.
Hall, E. T. (1960) The Silent Language. Garden City, NY: Doubleday.
Hall, E.T. (1966) The Hidden Dimension. Garden City, NY: Doubleday.
Rowell, T. (1972) The Social Behaviour of Monkeys. Harmondsworth: Penguin Books.
Smutts, B., Cheney, D. Seyfarth, R., Wrangham, R. and Struhsaker, T. (1987) Primate Societies, Chicago: University of Chicago Press.
Zimmerman, E., Newman, J.D. and Jurgens, U. (1995) Current Topics in Primate Vocal Communication. New York: Plenum Press.
Readings for Lecture # 2
Cheney, D. and Seyfarth, R. (1990) How Monkeys See The World. Chicago: University of Chicago Press.
Parker, S.T. and Gibson, K.R. (1990) 'Language' and Intellegence in Monkeys and Apes. Cambridge: Cambridge University Press.