Part IV: Nonhuman Primate Communication

It is thought that animal communication and human language(s) have fundamental differences in their structures and functions (Fitch 2000; Janik and Slater 2000; MacNeilage 1998; Beaken 1996:103; Hauser 1996; Ujhelyi 1996). According to Tomasello and Call (1997:232) animal communication is a “ritualized social act designed to induce others to act via their own self directed powers”. These signals are thought to express the animal’s emotional states, which in turn motivates the resultant behavioural actions of conspecifics in given circumstances (Hauser 1996; Tomasello and Call 1997). Furthermore, in animal communication, a rather limited set of messages appears to be transmitted, which are in general, genetically fixed (ibid.). However, there seem to be several exceptions, for example, the existence of different vocal signs for different predators in vervet monkeys (Cheney and Seyfarth 1990, 1997; Hauser 1996; Tomasello and Call 1997).

Although some researchers believe that symbolism is found among primates, it is not thought to be necessarily found in their natural communication system (Aitchison 1998:20). It has been proposed that the alarm calls of vervet and squirrel monkeys may represent an intermediate stage en route to symbolization (Tomasello and Call 1997; Hauser 1996). Human raised chimpanzees, who have been taught language like systems, can use signs as symbols, yet do so mainly when they require something (ibid.). However, the realization of the potential power of names, and the subsequent desire to label everything, has not been found in these experiments, although it occurs in human children between the ages of one and two (Aitchison 1998:21; Tomasello and Call 1997).

Human speech has also been distinguished from nonhuman primate gesture call systems by virtue of its representational level. According to Knight (1998:69), linguistic reference is not a direct mapping from linguistic terms either to perceptible things or to intentional states. Instead the mapping is from linguistic terms to communal constructs and representations established in a structured discourse (ibid.). Human vocal activity may have evolved from instinctive animal vocalizations (Beaken 1996:103). Specifically those of social interaction and emotional expression (akin to those of infants). However, the early vocalizations of infants are quite different from the speech patterns of adult human beings.

Ulbaek (1998:33) believes that language evolved from animal cognition, not communication. Ulbaek (1998:34-46) claims that the following are examples of cognitive abilities in nonhuman animals specifically, primates (Ulbaek 1998:34-36). : 1) tool making and usage (termite ‘fishing sticks’, ‘hammer and anvil’ stones for cracking nuts); 2) cognitive maps (knowledge of their territory to plan routes to food areas); 3) learning through imitation; 4) social knowledge (dominance hierarchies); 5) deception; 6) theory of mind (knowledge of the intentions of others); and 7) ability to learn language like systems (based on experimentation).

The main argument against nonhuman primate communication as a precursor of modern human language is the lack of conclusive evidence that nonhuman primates possess a theory of mind. The theory of mind hypothesis states that humans attribute mental states, such as knowledge and beliefs, to others, and that there is a recognition of the causal relationship between mental states and behaviour (Dunbar 1998; Worden 1998, Tomasello and Call 1997; Seyfarth and Cheney 1997:250; Gibson and Ingold 1993). Nonhuman primates appear to recognize one another as individuals, know all about each others’ kin and alliance relations, and can rapidly learn simple rules about who will do what in specific circumstances (Worden 1998:151; Tomasello and Call 1997, 1993). To have social intelligence, primates need to do three things (ibid.): 1) represent in their minds information about social situations, past and present; 2) to learn and represent internally, the causal regularities whereby one social situation leads to another; and 3) to combine knowledge of the present social situation with knowledge of causal regularities to predict what may happen next.

Based upon the criteria for theory of mind, nonhuman primates may have communication systems which are semantic, but do not qualify as a ‘language’ since they are not ‘intentional’ (Tomasello and Call 1997; Hauser 1996). While it appears that most primates do not possess a theory of mind, the picture in great apes is unclear. Some evidence from field studies suggests that they do, while laboratory studies are more negative (ibid.). However, since these laboratory studies are modeled upon similar experiments with preschool human children, and require a verbal response to correlate observed behaviours, the lack of evidence for theory of mind in nonhuman primates is questionable (Aitchison 1998; Tomasello and Call 1997). Since it is known that it takes several years before human children ‘acquire’ a theory of mind, and there is, as yet, no way to know with any certainty what nonhuman animals ‘intend’ or ‘mean’ when they vocalize, this section will focus upon the interpretations of observed and playback experiments of nonhuman primate vocalizations.

It has been suggested that there is no living species which demonstrates an intermediate stage of language evolution (Ujhelyi 1996:74). This should not be a surprising observation, since the intermediate stage of language origins should, theoretically, lay within the early hominid lineage. According to evolutionary theory, the nonhuman primate and hominid lineages ‘split’ approximately six to eight million years ago (Tattersall and Schwartz 2000). For instance, it has been proposed that chimpanzees have remained physiologically unaltered for the last five million years, while the hominid lineage has undergone at least 17 ‘speciations’ with associated physiological changes during that same period of time (ibid.). All of following lines of inquiry of nonhuman primate communication should be viewed as possible modes by which later hominids incorporated into early linguistic forms.

The homologies between language and animal communication have been questioned by a variety of researchers (Burling 1993; Tomasello and Call 1997; Cheney and Seyfarth 1990a). It is generally agreed that most aspects of human vocal production are shared with a variety of other animals, thus it can be examined from the perspective of comparative evolution (Fitch 2000:258). One can hypothesize that the ability to vary the arrangement of vocal elements, and to produce meaning differences, may be the source of language origins (Ujhelyi 1996:71).

There are three main problems with research concerning nonhuman primate communication: 1) it has tended to focus upon the following specific types of communication: alarm calls, long (distance) calls, response calls, and duetting; 2) very few nonhuman primates have been intensively studied (i.e. vervet monkeys, diana monkeys, macaques, chimpanzees, gibbons); and 3) there is a sharp division between the interpretation of observational field reports of wild nonhuman primates, and the analysis of playback experimental studies conducted upon both wild and captive nonhuman primates. Specifically, the anecdotal evidence seems to imply that nonhuman primates have a rich social life inclusive of specific referential communication among conspecifics, whereas playback studies point to simpler, behavioural mechanisms.