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Gestures of apes and pre-linguistic human children: Similar or different?

May 2008
First Language 28(2):116-140

May 2008
28(2):116-140

Authors:

Universität Osnabrück

The majority of studies on animal communication provide evidence that gestural signalling plays an important role in the communication of non-human primates and resembles that of pre-linguistic and just-linguistic human infants in some important ways. However, ape gestures also differ from the gestures of human infants in some important ways, and these differences might provide crucial clues for answering the question of how human language — at least in its cognitive and social-cognitive aspects — evolved from the gestural communication of our ape-like ancestors. This article provides an overview on the gestural signalling of monkeys and apes to enable a comparison with gestures in pre- or just-linguistic children. Implications for the evolution of language are discussed.

Total number of gestures used by different apes, divided into the three main signal categories

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www.sagepublications.com Vol 28(2): 116–140 (200805)

DOI: 10.1177/0142723707080966

Gestures of apes and pre-linguistic human

children: Similar or different?

Simone Pika, University of Manchester

ABSTRACT

The majority of studies on animal communication provide evidence that ges-

tural signalling plays an important role in the communication of non-human

primates and resembles that of pre-linguistic and just-linguistic human

infants in some important ways. However, ape gestures also differ from

the gestures of human infants in some important ways, and these differ-

ences might provide crucial clues for answering the question of how human

language – at least in its cognitive and social-cognitive aspects – evolved

from the gestural communication of our ape-like ancestors. This article pro-

vides an overview on the gestural signalling of monkeys and apes to enable

a comparison with gestures in pre- or just-linguistic children. Implications for

the evolution of language are discussed.

KEYWORDS

Apes; development; evolution of language; gestures; human children; learning

Language in humans (Homo sapiens) is traditionally described as communication by

word of mouth. One of the puzzling questions about language is how it came to

be the province of the oral modality, and recent genetic evidence has suggested

that our hominid ancestors probably lacked some of the key capacities for normal

speech production, perhaps until as little as 200,000 years ago (Enard et al., 2002).

These findings indicate that many of the cognitive building blocks required for

language processing must be substantially older, having evolved in the primate

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lineage long before the advent of speech in modern humans. One important approach

is therefore the comparative approach, which, with regard to language evolution,

pinpoints similarities and differences between human language and the communica-

tion systems evolved in our closest living relatives, the nonhuman-primates (hereafter

primates) (e.g., Hauser & Konishi, 1999; Snowdon, Brown & Petersen, 1982).

The primate lineage or the order primates consists of prosimians, monkeys, apes

and humans. Humans, together with the five great ape species – chimpanzees

(Pan troglodytes), bonobos (Pan paniscus), gibbons (genus Hylobates), gorillas

(Gorilla gorilla) and orangutans (Pongo pygmaeus) – belong to the superfamily

Hominoidea (following the taxonomy of Fleagle, 1999). Humans are most closely

related to bonobos and chimpanzees, with whom they share around 95% of the

same DNA (Britten, 2002). The Hominoids split off from the other primates (Old

World monkeys, New World monkeys, and prosimians) an estimated 23 million years

ago, and the human/chimpanzee divergence occurred approximately 5 million years

ago (Kumar, Filipski, Swarna, Walker & Hedges, 2006).

Studies on the communicative skills of primates have mainly focused on vocaliza-

tions (e.g., Marler, 1977; Seyfarth, 1987; Snowdon, 1988; Zuberbühler, 2003). In the

1960s Struhsaker (1967) made the discovery that vervet monkeys (Cercopithecus

aethiops) utter different, distinct alarm calls in response to different predators. The

additional finding that vervet monkeys also use the information encoded for different

escape responses, such as hiding in bushes and climbing a tree (Seyfarth, Cheney &

Marler, 1980), raised the possibility that some primates, like humans, also use vocal-

izations to make reference to outside entities (Cheney & Seyfarth, 1990).

Referential signals have been reported from various monkey species in their natural

habitats (e.g., Zuberbühler, 2000). But it has been found that alarm calls of this type

are a common phenomenon in species that must also organize different escape

responses for different predators, for instance prairie dogs and domestic chickens

(for an overview, see Owings & Morton, 1998). Importantly, there is currently no

evidence that any species of ape has developed such referent specific alarm calls.

In addition, studies focusing on the referential use of other vocalizations of

apes, e.g., long-distance calls, provided mixed results (e.g., Clark & Wrangham,

1993, 1994; Crockford & Boesch, 2003; Marler & Hobbett, 1975; Mitani & Brandt,

1994; Mitani, Hasegawa, Gros-Louis, Marler & Byrne, 1992; Slocombe &

Zuberbühler, 2005). Furthermore, the majority of studies on primate vocalizations

revealed that call morphology and call usage seem to have only limited flexibility

(Corballis, 2002; Liebermann, 1998). Recent data on some primate species in their nat-

ural habitats have provided evidence for audience effects of vocalizations (Caine,

Addington & Windfelder, 1995; Cheney & Seyfarth, 1985; Mitani & Nishida, 1993),

categorical perception of vocalizations (Masataka, 1983), acoustic ‘rules’ regulating

vocal exchange (Sugiura, 1993), flexibility of vocal production (Sugiura, 1998), the abil-

ity to combine calls into higher-order sequences that have a particular meaning (Arnold

& Zuberbühler, 2006) and vocal learning (Crockford, Herbinger, Vigilant & Boesch,

2004; Mitani et al., 1992), but the comparative approach has not proved very suc-

cessful. It mainly revealed that the two sorts of communication are so different that a

comparison between them provides little insight about their common ancestry.

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In addition to the acoustic modality, however, human speech embodies another

means of communication: movements of the arms and hands, termed gestures

(McNeill, 1985). The study of gestures has received tremendous research attention in

recent years (e.g., Goldin-Meadow & Mylander, 1998; Iverson & Goldin-Meadow,

1998; Kendon, 1975; McNeill, 1992; Morris, Collett, Marsh & O’Shaughnessy, 1979;

Pika, Nicoladis & Marentette, 2006), which might be partly due to the fact that many

evolutionary stories involve an initial stage in which language was carried out in

gesture (Arbib, 2002; Armstrong, Stokoe & Wilcox, 1995; Condillac, 1971; Corballis,

2002; Hewes, 1973; Hockett, 1978). In addition, it is thought that gestures form a

single, integrated system with speech (McNeill, 1985), and can provide insight into an

individual’s mental representations and cognitive skills (e.g., Goldin-Meadow,

Nusbaum, Kelly & Wagner, 2001; Iverson & Goldin-Meadow, 1998; McNeill, 1992;

Nicoladis, Mayberry & Genesee, 1999). Moreover, within deaf cultures where the

oral modality is not accessible, full-fledged sign languages have evolved in the man-

ual modality and function without any use of speech at all (Klima & Bellugi, 1979).

Interestingly, to some extent human-reared great apes are able to master gestural

or ideographic communication systems (e.g., Gardner, Gardner & Van Cantford, 1989;

Savage-Rumbaugh, Murphy, Sevcic, Brakke, Williams & Rumbaugh, 1993). Though

by no means ‘language’, these projects provided evidence for the intentional, re-

ferential use of numerous gestures and ideograms (Savage-Rumbaugh, McDonald,

Sevcic, Hopkins & Rupert, 1986), as well as understanding of human speech (Gardner

et al., 1989; Savage-Rumbaugh et al., 1993). Great apes, therefore, seem to be able to

use crucial aspects of language, given that the vocal-auditory channel can be by-passed.

In addition, primates also routinely use gestures in their natural communication,

and the present article aims to provide an overview of the state of the art, beginning

with primate gestural communication in general. In 1935 Ladygina-Kohts published

a detailed comparison of the expressive behavior of a juvenile chimpanzee and of

her own child, followed by modern ethological analyses of primate facial and ges-

tural communication in the 1960s (e.g., Van Hooff 1967; Van Lawick-Goodall,

1968). Two decades later Tomasello and colleagues (e.g., 1985, 1994, 1997a,

1997b) introduced a new approach, which was inspired by the study of gestural

communication in human children and focused on the underlying processes of social

cognition, including learning mechanisms and flexibility of gesture. The majority of

the resulting studies investigated common chimpanzees (Pan troglodytes), but more

recently the work was expanded to cover other ape species (e.g., Liebal, Call &

Tomasello, 2004b; Liebal, Pika & Tomasello, 2006; Pika, Liebal, Call & Tomasello,

2005a; Pika, Liebal & Tomasello, 2003, 2005b).

I will therefore focus mainly on

these and related studies by addressing the following aspects:

• gestural repertoire;

• the development of gestures;

• the learning of gestures;

• the referential use of gestures;

• similarities and differences between the gestures of apes and pre- or just-

linguistic human infants.

I will concentrate on studies that might be of most interest to researchers investi-

gating human gestural communication.

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PRIMATE GESTURAL COMMUNICATION

To date, studies investigating the gestural communication of primates are very

unevenly distributed among species (for an overview, see Tomasello & Call, 2007)

and concern mainly apes. There are only a few reports on the use of gestures in

monkeys.

Monkeys

Kummer (1968) described notifying behavior in Hamadryas baboons (Papio

hamadryas). This behaviour consists of approaching another animal and

looking directly into her face and occurs mainly when an individual leaves others in

a troop. One possible explanation of this behaviour is that the signaller wants to

make sure that the recipient is attending before engaging in certain activities. In

addition, Kummer & Kurt (1965) described an auditory

gesture, the so called

ground-slap that seems to serve as an attention-getter and a kind of teasing behav-

iour during play. Furthermore, Maestripieri (1997, 1999, 2005) provided a very

detailed insight in the gestural behaviour of macaques, focusing on three different

species in captivity (Macaca arctoides, M. nemestrina, M. mulatta). His data

showed that rhesus macaques (M. mulatta) have a relatively limited gestural

repertoire, pigtail macaques (M. nemestrina) possess conspicuous signals of affilia-

tion and bonding, and stumptail macaques (M. arctoides) have the richest repertoire

of assertive and submissive signals. Most similarities among species were found

in signals of dominance and submission, and most differences in affiliative gestures

and bonding patterns. These results therefore indicate that characteristics of a social

structure, such as reduced influence of dominance and kinship, may select along

with group size for a wider gestural repertoire in a given species. In addition,

Maestripieri (1996) observed a very interesting behaviour between pigtail

macaque mothers and their infants: when the infant does not want to follow the

mother, the mother sometimes returns and stares in the infant’s face (or even pokes

the infant).

Apes

The gestural communication of apes has received much more research attention,

with the majority of studies focusing on common chimpanzees. Following an etho-

logical approach, Van Lawick-Goodall (1968) and Van Hoof (1973) published the first

chimpanzee behavioural repertoires (so-called ethograms). These also included

detailed descriptions of communicative and non-communicative behaviours and

therefore also many of the communicative gestures that have been observed in later

studies in the wild and in captivity. Nishida, Kano, Goodall, McGrew & Nakamura

(1999) published the most complete chimpanzee ethogram to date, which includes

a comparison with previous ethograms, particularly those developed by Goodall

(1986a, 1986b; Van Lawick-Goodall, 1968). In addition, it also includes a compari-

son with the behaviour of the closest related congener of the chimpanzee, the

bonobo (Pan paniscus). Various communicative behaviours of bonobos are men-

tioned in studies on wild populations at Lomako and Wamba in the Democratic

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Republic of Congo (e.g., Badrian & Badrian, 1984; Ingmanson, 1996; Kano, 1980;

Kuroda, 1980, 1984), but only researchers studying captive individuals addressed the

use of gestures in more detail (Savage-Rumbaugh & Wilkerson, 1978; Savage-

Rumbaugh, Wilkerson & Bakeman, 1977). Savage-Rumbaugh and colleagues, for

instance, described the use of 20 different gestures in the sexual context, and de

Waal (1988) provided a comparison of the gestural signalling of bonobos and chim-

panzees. Like many of its predecessors, this comparison had its roots in the etho-

logical tradition of cataloguing the different units of behaviour into comprehensive

repertoires.

The first ethograms of the behaviour of mountain gorillas were also conducted

in the second half of the last century (Fossey, 1974; Schaller, 1963, 1965). They con-

tained mainly communicative signals, such as species-typical displays (Fossey,

1974; Schaller, 1963, 1965). In their compilation of gorilla ethograms, Ogden &

Schildkraut (1991) mentioned a variety of auditory, tactile and visual gestures, and

Parnell & Buchanan-Smith (2001) described a specific gesture, the splash display,

for wild western lowland gorillas to intimidate other silverbacks. Fay (1989)

observed hand-clapping behaviour in gorilla females, but the most detailed

overview of gestures in captive gorillas was provided by Tanner & Byrne (1996,

1999). In addition, Tanner (2004) also described gesture-phrases and sequences

between two individuals in captivity.

In contrast to the African great ape species, substantially less is known about the

gestural communication of the Asian apes. MacKinnon (1974; but see also, Rijksen,

1978) provided a repertoire of tactile and visual gestures of wild Bornean (Pongo

pygmaeus) and Sumatran orangutans (P. abelii). Chivers (1974), Ellefson (1967,

1974) and Palombit (1992) compared the communicative behavior of wild siamangs

(Symphalangus syndactulus) and white-handed gibbons (Hylobates lar). In addition,

Fox (1977) and Orgeldinger (1999) reported a number of different tactile and visual

gestures

in captive siamangs and concluded that the siamang’s repertoire is gen-

erally limited in comparison to that of great apes.

GESTURAL REPERTOIRES

Gestures can be organized as a function of their main sensory modalities: auditory,

tactile and visual. Auditory gestures rely mainly on sound production (although they

also have an important visual component), tactile gestures depend mainly on estab-

lishing physical contact with the recipient, and visual gestures rely solely on visual

information.

Bonobos

Pika and colleagues (Pika, 2007a; Pika et al., 2005b) studied the communicative

behaviour of subadult bonobos (N  7) in two different groups in two zoos in

Europe and found that they used 20 different distinct gestures (see Fig. 1). Visual

gestures represented the most common sensory modality in bonobos (11 visual, 1

auditory, 8 tactile).

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Chimpanzees

Tomasello and colleagues (1985, 1989, 1994, 1997b) studied two groups of cap-

tive chimpanzees at the Yerkes Primate Research Center, Atlanta (USA) and found

that subadult individuals used between 25 and 30 gestures depending on the study

period (see also Liebal et al., 2004a). Combining all gestures from all studies pro-

duced a total of 38 gestures (20 visual, 4 auditory, 14 tactile; see Fig. 1).

Gorillas

Pika and colleagues (Pika, 2007b; Pika et al., 2003) described the use of 33 differ-

ent distinct gestures (16 visual, 6 auditory, 11 tactile) used by subadult gorillas

(N  13) living in two groups in two different zoos in Europe (see Fig. 1).

Orangutans

Liebal and colleagues (Liebal, 2007a; Liebal et al., 2006) focused on the perform-

ance of gestures in two orangutan groups in two different zoos in Europe and

found that subadults (N  7) used 26 different distinct gestures, with visual gestures

being the most common sensual modality (12 tactile, 14 visual; see Fig. 1).

Siamangs

Liebal and colleagues (Liebal, 2007b; Liebal at al., 2004b) investigated the use of

gestures in three family groups of siamangs in two different zoos in Europe and

reported that subadult siamangs (N  7) use a gestural repertoire of 17 different

distinct gestures, consisting only of tactile (10) and visual (7) signals; see Fig. 1).

Figure 1 Total number of gestures used by different apes, divided into the three

main signal categories

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DEVELOPMENT OF GESTURES

To investigate the development of communicatory signals in apes and to decide

whether they qualify as intentional acts, researchers have used the developmental

Piagetian and the preverbal communication perspective. Plooij (1978, 1979) was

the first researcher to study the ontogeny of communicatory signals in chimpanzees

in the wild, using Speech Acts Theory (see Austin, 1962; Bates, Camaioni &

Volterra, 1975). He observed mother-infant dyads of chimpanzees in Gombe,

Tanzania, and argued that, although the mother begins interpreting the baby’s

behaviour at birth, the neonatal chimpanzee does not perform any acts with a

social-communicatory intention. At the age of 3–11 months, the chimpanzee infant

starts to contribute to interactions with its mother by responding appropriately to

her behaviours. However, only between the age of 9 and 12

months does the

chimpanzee infant start to initiate interactions with its mother by intentionally

directing signals to her, e.g., by using gestures, such as initiating tickling, grooming

and approach. In addition, only at this age does the chimpanzee infant start to under-

stand its mother and conspecifics as social agents. This developmental stage therefore

marks the onset of the use of protoimperative or imperative gestures (Bates et al.,

1975; see definition on p. 126) and the developmental shift from perlocutionary to

illocutionary acts. In perlocutionary acts the communication occurs only because the

receiver is adept at interpreting the behaviour of the signaller, while in illocutionary

acts the signaller directs its behaviour toward a recipient (Bates et al., 1975).

Tomasello et al. (1997b) investigated the development of the gestural repertoire

in chimpanzees in captivity and found that the overall repertoire of one-year-old

chimpanzees consisted of 12 different gestures and reached a peak of 19 gestures

at 3 years of age. From this point on, the number of gestures remained stable, and

some gestures were replaced by others, e.g., gestures for nursing disappeared,

while gestures used for agonistic and sexual purposes became more prominent.

Concerning gesture sequences of chimpanzees, Liebal et al. (2004a) showed that

the length of the sequences decreased with age, with adults producing the short-

est sequences and juveniles the longest sequences.

Focusing on the development of gestures in gorillas, Pika et al. (2003) found an

increase in the mean number of gestures from 18.5 at the age of 3 to 24 at 4,

whereas the number of gestures decreased to 20.6 gestures at the age of 5–6. This

difference was not significant and Pika and colleagues argued that, due to the short-

est infancy and juvenile stages of all apes (Bogin, 1999), gorillas develop certain

aspects of physical maturity and intellectual development at a younger age (e.g.,

Antinucci, 1990; Parker, Mitchell & Lyn Miles, 1999; Redshaw, 1978; Spinozzi &

Natale, 1989).

Bard (1992) studied the communicative abilities of orangutan infants in the

food-sharing context, focusing on a different aspect of development: the transition

from bifocal behaviour to behavioural sequences. Bard (1992) distinguished

between ‘intentional behaviour’ (bifocal behavioural sequences involving either

objects or social agents; Case, 1985) and ‘intentional communication’ (behavioural

sequences involving coordination between social agents and objects; e.g.,

Bretherton, McNew & Beeghly-Smith, 1981). She showed that orangutans at the

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age of 1–6 months used intentional behaviours, whereas intentional communica-

tion was observed in older orangutans only, ranging from 2

to 5 years of age. In

intentional behaviour, individuals directed their action to the food, for instance,

with a grasp coordinated with eating, or they directed their behaviour to the

mother, for instance, by performing a pull on the mother’s body and subsequently

eating. In intentional communication, on the other hand, individuals solicited food

from the mother by using one open, cupped hand, palm up, held underneath, but

not necessarily touching, the mother’s chin. In addition, Liebal (2007a) showed that

the median number of gestures increased from 9 to 17 in one infant orangutan and

from 9 to 16 in juvenile and subadult orangutans, and decreased in adults to 12

gestures.

Investigating the development of gestures in siamangs, Liebal et al. (2004b) reported

that the gestural repertoire of siamang infants consisted of 8.5 gestures and reached a

peak at the age of 4–5 years (11 gestures). From this point on, the number of gestures

also seemed to remain quite stable, and some gestures were replaced by others.

LEARNING OF GESTURES

Focusing on learning processes, scientists distinguish between social and individual

learning. Social learning can be defined as ‘a group of learning mechanisms in

which observation of other individuals facilitates or enables the acquisition of a

novel behavior’ (Call, 1999: 317). Researchers tend to discriminate at least four

main phenomena: social facilitation, local and stimulus enhancement, emulation,

and imitation (for an overview see, e.g., Heyes, 1994; Whiten & Ham, 1992; Zentall,

2001). In contrast, in ‘individual learning’ two or more individuals independently

acquire the same behaviour through encountering and being shaped by similar

learning environments (Whiten & Ham, 1992).

Observations of wild chimpanzee populations provide evidence for the existence of

cultural variation among chimpanzee communities or unit-groups (Whiten et al.,

2001). Nishida (1980), for instance, reported the use of the gesture leaf clipping in the

Mahale K group, in Tanzania. In this gesture an individual takes 1–5 very stiff, dried

leaves and strips them in its mouth, making a distinctive and fairly loud noise. The ges-

ture was used in the sexual context, during play or frustration and was later also

recorded in the chimpanzee community of Bossou, Guinea (Sugiyama, 1981), and in

the chimpanzee community of Taï, Ivory Coast (Boesch, 1995). Interestingly, the indi-

viduals at Bossou use it mainly in the context of frustration or during play, whereas the

males at Taï use it mainly as part of a drumming display. Another group-specific ges-

ture used by chimpanzees in the wild is the grooming hand clasp. In this gesture two

chimpanzees clasp both their right or both their left hands overhead, while parallel

grooming each other with the other hand (McGrew & Tutin, 1978). This gesture has

been observed at the study sites Taï, Ivory Coast, Lopé in Gabon, Mahale in Tanzania,

and Kibale in Uganda (for an overview, see Whiten et al., 2001), and also recently in

bonobos at the study site Lui Kotal, DRC (Fruth et al., 2006).

In both these cases, social learning is likely to be involved – for instance, by local

enhancement as individuals watch others groom under the armpits of receivers or

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watch others clip leaves and receive attention. Further evidence for the possibility

of some form of social learning or imitation in the genesis of gestures has been pro-

vided by studies on captive apes (e.g., Pika et al., 2005b). Focusing on gorillas, Pika

et al. (2003) described the use of the gestures armshake and chuck-up, which were

used by multiple individuals within a particular group but were not used by the indi-

viduals in any other group.

Tomasello et al. (1994), studying the acquisition of gestures in chimpanzees in

captivity, found no evidence for a social learning process. They suggested that the

main learning process involved in the acquisition of gestures is an individual learning

process called ‘ontogenetic ritualization’. In ontogenetic ritualization, a communica-

tory signal is created by two individuals shaping each others’ behaviour in repeated

instances of an interaction (Tomasello & Call, 1997).

The general form of this type of learning is:

• individual A performs behaviour X;

• individual B reacts consistently with behaviour Y;

• subsequently, B anticipates A’s performance of X, on the basis of its initial

step, by performing Y; and

• subsequently, A anticipates B’s anticipation and produces the initial step in a

ritualized form (waiting for a response) in order to elicit Y.

This means that a behaviour which was not at first a communicative signal becomes

one by virtue of the anticipations of the interactants over time (Tomasello & Call,

1997). For example, touching is an important part of mother-infant interactions in

gorillas to request drinking, and many individuals come to use a stylized reach-arm

to indicate that they are about to touch the mother and drink (Pika et al., 2003). In

orangutans, infants suck on the mother’s lips while she is eating to obtain food

pieces from her (Bard, 1990). Not until later, at an age of about 2.5 years (Bard,

1990), do they start to produce gestures, such as approaching the mother’s face to

beg for food without actually touching her mouth (Liebal et al., 2006).

Another important comparison for understanding the processes involved in

learning is the degree of commonality of the individuals within a single social group

and between social groups, who have never been in contact with one another. High

levels of concordance of gestural repertoires within a group and group-specific ges-

tures would provide evidence for the existence of a social learning process, whereas

individual differences that overshadow group differences (i.e., a lack of systematic

group differences, idiosyncratic gestures) imply that an individual learning process

is mainly involved. To assess the degree of commonality in the performance of ges-

tures between and within groups of apes, Pika et al. (2005a) used Cohen’s Kappa

statistics, with an individual either agreeing or disagreeing on the performance of

each gesture as compared with each other individual (cf. Tomasello et al., 1997b).

Interestingly, the within-group and between-group variability of all five ape species

did not differ significantly in any species, suggesting that social learning, in the form

of some kind of group-specific cultural transmission, is not the major learning

process at work. Further support for this view was provided by the fact that all great

ape groups had multiple individuals who used idiosyncratic gestures – used by

single individuals only – presumably not learned from any other individual (but the

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siamangs had no idiosyncratic gestures). These gestures involved recurrent events in

the ape’s life (e.g., food, play), they were accompanied by the signaller’s expect-

ation to receive a response (indicated by response waiting), and they most often

received a response in the form of an action or a responding gesture. These results

imply that the idiosyncratic gestures resembled a relatively stable part of a particular

youngster’s gestural repertoire and were understood by receivers (Pika et al., 2003;

Pika et al., 2005a).

Furthermore, great apes seem to be able to copy gestures based on facilitation

of pre-existing repertoire (Byrne & Tanner, 2006). The first report stems

from an experiment with a single home-reared chimpanzee (Hayes & Hayes, 1952),

using a so-called ‘do-as-I-do’ design: the individual is first trained to copy ges-

tures that are demonstrated to her by the experimenter; then ‘arbitrary gestures’,

not previously demonstrated, are introduced as a test of the ability to imitate.

Custance et al. (1995) replicated the experiments with two nursery-reared chim-

panzees and confirmed the basic phenomenon. In the report of Hayes & Hayes

(1952), sparse documentation of the results had made interpretation problematic,

but Custance et al. (1995) asked two independent, naïve observers to judge after

each demonstration which of 48 possible actions the behaviour of the chimpanzee

most resembled. They found significant matching, although the chimpanzees’ copy

was often imperfect. In addition, the same set of stimuli were used with another

ape species, a language-trained orangutan (Miles, 1986). The orangutan received

spoken commands in English and showed detectable but imperfect copying (Call,

2001). More recently, Byrne & Tanner (2006) reported a version of the do-as-I-do

procedure with a nursery-reared gorilla. However, whereas previous experiments

used reinforcement techniques to teach the procedure to the apes, the gorilla was

not rewarded and copied the gestures spontaneously. This gorilla’s gestural per-

formance was very similar to that of the other great apes. However, note that none

of the apes was raised by its natural mother, suggesting that a high orientation of

behaviour towards humans may be essential to elicit this ability (Byrne & Tanner,

2006).

Overall, the reviewed data therefore suggest that individual learning is the main

learning process involved in the acquisition of gestures. But the possibility of some

form of social learning in the genesis of special gestures cannot be denied.

REFERENTIAL USE OF GESTURES

So far we have looked at gestures in terms of gestural repertoires, development,

commonalities and individual differences. One other important question is whether

apes use gestures referentially, i.e., that they use them to attract the attention of

others to some outside entity, for example, an event or an object. This aspect is of

special importance because the recipient must infer the signaller’s intended meaning,

which might indicate some important skills in the ability to share attention with

others (Camaioni, 1993; Tomasello, 1995).

Referential gestures are always triadic, because they include a signaller, a recipi-

ent and a third entity or event. Although this ‘third entity’ mainly denotes an

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outside entity (Bates, 1976), it can also include an inside entity, e.g., referring to

one’s own nose. In addition, Bates et al. (1975) differentiated between protoimper-

ative and protodeclaratives. Protoimperatives are defined as the child’s preverbal

intentional use of the listener as an agent or tool in achieving some end (e.g., to

request an object). Protodeclaratives are defined as the child’s preverbal effort to

direct the adult’s attention to some event or object in the world. This approach sug-

gests continuity between preverbal and later verbal communication and is useful

when focusing on human children whose gestures precede speech (Bates et al.,

1979). However, it is not coherent to use the term ‘proto-’ imperatives or declara-

tives in species who will never exhibit symbolic communication (Leavens, 2004;

Leavens & Hopkins, 1998). I will therefore use the term imperative to refer to ges-

tures being used to get another individual to help in attaining a physical goal, such

as getting an object, playing, etc., and the term declarative to characterize those

gestures which are used to attain a non-physical goal, namely to draw another’s

attention to an object or entity merely for the sake of sharing attention.

Referential gestures, such as imperative pointing, have been reported for captive

chimpanzees interacting with their human experimenters (Leavens, Hopkins & Bard,

1996; Leavens, Hopkins & Thomas, 2004). This ability was discovered by accident

while testing a chimpanzee on a matching-to-sample task, in which correct res-

ponses resulted in the delivery of a food reward by a feeder to a tube connected to

the cage mesh (Leavens et al., 1996). Occasionally, a food reward would overshoot

the pipe and land on the floor outside the cage. One day, the chimpanzee Clint was

observed to repetitively vocalize, point with his index finger (sticking his index

finger through the cage mesh), and alternate his gaze between a fallen food reward

and the experimenter. This observation led to controlled experiments, which clearly

showed that chimpanzees use intentionally-produced pointing gestures to request

food (e.g., Leavens & Hopkins, 1999). Further evidence for imperative pointing has

been provided by human-raised individuals, who were first trained in some kind of

communication with humans that involved close-range pointing (e.g., Call &

Tomasello, 1994; Gardner & Gardner, 1969; Krause & Fouts, 1997; Miles, 1990;

Patterson, 1978a; Savage-Rumbaugh et al., 1986; Woodruff & Premack, 1979). In all

cases, however, the apes then began spontaneously to point for humans in more flex-

ible ways, e.g. to more distant objects they wished to have or to locations that they

wished to visit, or even in a declarative way to share attention (see Miles, 1990, 1999).

Focusing on the use of pointing gestures of individuals in populations in the wild,

anecdotal observations indicate that chimpanzees of the Bossou community in Guinea,

where animals use stones in a hammer and anvil fashion to crack oil-palm nuts, have

been observed to point to a stone (once) and to nuts (nine times) (Inoue-Nakamura &

Matsuzawa, 1997). Interestingly, a report by Vea & Sabater-Pi (1998) provided the only

anecdotal evidence for the use of a declarative pointing gesture by a bonobo male in

the wild: he was sitting in a tree and pointed to the position of two groups of human

observers, who tried to hide in nearby undergrowth. He alternated his gaze between

his group members and the humans then repeated the pointing gesture twice while

emitting vocalizations. Considerable debate continues about whether apes point in a

referential way, and it remains unclear whether pointing represents a natural commu-

nication ability or is simply a by-product of living in a human encultured environment

(Tomasello & Call, 1997).

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Patterson (1978b), Savage-Rumbaugh (1988) and Savage-Rumbaugh,

Rumbaugh & McDonald (1985) described the use of a declarative gesture: the ges-

ture ‘showing’ in one human-raised gorilla, and in one human-raised bonobo. It

should be noted, however, that in all cases interpretation is an issue and that the

declarativeness might only exist in the eyes of the human beholder. In addition,

Savage-Rumbaugh and colleagues (Savage & Bakeman, 1978; Savage-Rumbaugh

et al., 1977) and Tanner & Byrne (1996) reported the use of several gestures that

they consider iconic uses of gestures. Iconic gestures are related to their referent by

virtue of some actual physical resemblance between the two (Bates, Benigni,

Bretherton, Camaioni & Volterra, 1979), such as a desired motion in space or the

form of an action. One male bonobo and one male gorilla seemed to signal

with their hand, arm or head to a playmate the direction in which he wanted her

to move, the action he wanted her to perform, or the position he wanted her to

take. Roth (1995) and Pika et al. (2003) tried to find evidence to support these find-

ings by studying three groups of bonobos and two groups of gorillas in captivity,

but did not observe any instances of the iconic use of gestures. There might be several

explanations: (a) the iconicity existed in the eyes of the human observers only

(Tomasello & Call, 1997) and did not fulfil a function for the sender and the

recipient; (b) the analyses of Roth (1995) and Pika et al. (2003) did not focus in sufficient

detail on the receiver’s response to detect gestures of an iconic nature; or (c) gesturing

of an iconic nature represents a developmental phenomenon and appears only at ado-

lescence, promoted by special social and physical conditions (Tanner & Byrne, 1999).

In a recent paper, Pika & Mitani (2006) describe the first observation of a widespread

use of an indicative gesture by chimpanzees in the wild. The so-called directed scratch

gesture was observed between adult males of the Ngogo community, Kibale National

Park, Uganda. It involved one male chimpanzee making a relatively loud and/or exag-

gerated scratching movement on a part of his body, which could be seen by his groom-

ing partner (see Fig. 2). In the majority of the observed cases the grooming individual

immediately stopped grooming and started to groom the indicated spot.

Pika & Mitani (2006) therefore suggest that: (1) the gesture may be used com-

municatively to indicate a precise spot on the body and to depict a desired future

action, namely grooming, and (2) the recipient of the signal has an understanding

of the intended meaning of the gesture. They concluded that directed scratches

therefore may qualify as referential.

In sum, the evidence provided shows that apes use referential gestures, such as

imperative pointing, or declarative gestures with human experimenters or caretakers.

In addition, apes use imperative, referential gestures in their natural communication

with conspecifics.

SIMILARITIES AND DIFFERENCES BETWEEN THE GESTURES

OF APES AND PRE- OR JUST-LINGUISTIC HUMAN INFANTS

The studies reviewed above provide evidence that apes develop multifaceted

gestural repertoires and, similar to human children, they use their gestures as inten-

tional acts. The majority of their intentional gestures are dyadic, i.e., used to attract

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the attention of others to the self, not triadic, to attract the attention of others to

some outside entity. Exceptions are the gestures directed scratch (Pika & Mitani,

2006), food begging (i.e., an animal holds out the hand, palm up to obtain food

from another; for chimpanzees, see Tomasello et al., 1994; for orangutans, see

Bard, 1992), food offer (an animal offers food placed on her arm to another one;

Liebal et al., 2006) and pointing. These gestures are clearly triadic – a request to

another for grooming or food, or an offer of food to another.

Human children, however, gesture from their very first attempts at gestural com-

munication before language, using both dyadic and triadic gestures (Carpenter

et al., 1998), but a quantitative comparison between the gestural performance of

apes and pre-linguistic children has not yet been made. Such an approach could

clarify in much more detail the role different types of gestures play in the commu-

nication of apes and of pre-linguistic children.

Concerning the type of gestures produced, researchers of pre-linguistic com-

munication distinguish between ritualizations, deictics and symbolic gestures

(Lock, 1978; for more detailed categorization, see also: Acredelo & Goodwyn, 1988;

Iverson, Capirci & Caselli, 1994; Pizzuto, Cameracann, Corazza & Volterra, 1994). Apes

perform ritualizations, in which the signaller uses an effective behaviour for a request.

Figure 2 The directed scratch (© Dorothee Classen)

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For instance, apes often use a stylized arm-raise to initiate play, ritualized from actual

acts of play hitting in the context of rough-and-tumble play. In addition, many young-

sters ritualize signals for asking the mother to lower her back so that they can climb

on, for example, a brief touch on the top of the rear end, ritualized from occasions on

which they pushed her rear end down mechanically. Human children often use similar

gestures, such as raising their arms to be picked up. Ontogenetic ritualization seems

to be the learning process involved, which does not involve understanding of commu-

nicative intentions or cultural (imitative) learning of any sort. Thus, it does not create a

shared communicative symbol (Tomasello, 2003).

The second type of gestures, deictics, involves a signaller, a recipient and some

outside entity, and typically begins in human children around the age of 10 months.

Although a third entity is involved, the use of deictics does not automatically imply

that the human infant is using them in order to share attention with the adult on

that third entity. For example, Moore & D’Etremont (2001) showed that many infants

use arm and index finger extension to orient their own attention to things. Thus,

pointing is for some infants just another ritualization and they produce the signal

although they still do not understand the function of it (Carpenter et al., 1998;

Franco & Butterworth, 1996). The reverse dissociation also exists in which infants

visually follow adult pointing but do not themselves produce the gesture (Carpenter

et al., 1998; Franco & Butterworth, 1996). Therefore, infants who learn to point via

ritualization understand their pointing simply as a procedure to achieve a certain goal

and not as a mutually understood communicative symbol to share attention.

However, if infants learn to point via imitation, they are learning by understanding

an adult’s communicative intention in using the gesture first and then engaging in

role reversal imitation to use the gesture her/himself when s/he has ‘the same’ com-

municative intention. To date, there has been no systematic research investigating

which learning process is involved in the acquisition of deictics or if infants use in-

dividual learning strategies.

Substantially more studies have been made on the motives of pointing. Researchers

differentiate three main motivations:

1. Pointing for imperative purposes, e.g., to request an object which is out of

reach; Bates et al., 1975.

2. Pointing for declarative purposes, e.g., holding up an object and showing

it; Bates et al., 1975.

3. Pointing to inform another person, e.g., of the location of an object;

Liszkowski, 2005.

Imperative pointing requires only conceiving the other person as an animate ‘agent’

of action and is used simply to influence the other’s behaviour. Declarative pointing,

on the other hand, has been defined as a means to obtain adult’s attention (‘laugh-

ter, comment, smiles and eye contact – which we have termed “attention”’; Bates

et al., 1975: 216). However, note that the most recent formulations of imperative and

declarative communication define these modes of communication by reference to

underlying psychological processes, or mental states (Liszkowski, Carpenter, Henning,

Striano & Tomasello, 2004; Tomasello, 1995; Tomasello, Carpenter & Liszkowski, 2007).

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In informative pointing, the providing of information is not to engage mutually about

an event or referent but, instead, mainly to benefit the other person (Liszkowski,

Carpenter, Striano & Tomasello, 2006). Informative pointing therefore reflects sensi-

tivity to others as agents with informational states (Liszkowski, Carpenter & Tomasello

et al., 2007).

Some gestures of great apes such as pointing are clearly deictic, and some gestures

such as food offer, food-begging and directed scratches seem to bear some resem-

blance to deictics: food offer and food-begging are clearly triadic, somehow distal

(because the signaller is not touching the recipient) and are used to point out

something specific. In addition, the gesture directed scratch clearly involves some

form of reference, but this reference is, in contrast to the other examples,

self-directed. Overall, however, all these gestures are used as effective procedures to

achieve a certain goal, but examples of apes using declarative or informative deictics

in their natural communication are so far unknown.

The third gesture type are symbolic gestures that are either associated with a

referent metonymically (the gesture refers to an element or attribute of something

to mean the thing itself) or iconically (Acredelo & Goodwyn, 1988; Pizzuto &

Volterra, 2000). Examples for human children are sniffing for a flower, panting for

a dog, holding arms out for an airplane, raising arms for big things, and blowing

for hot things. There is no research so far investigating whether symbolic gestures

are acquired via ritualization or via imitation (Lock, 1978). However, it seems much

more likely that in most cases infants are learning these symbolic gestures via

imitative learning.

On the surface there seems to be no example of apes’ gestures that bear some

resemblance to symbolic gestures. Nevertheless, group specific gestures such as

leaf clipping (Nishida, 1980), the grooming hand clasp (McGrew & Tutin, 1978),

somersault (Pika et al., 2005b) and armshake (Pika et al., 2003) suggest that social

learning, in the form of some kind of group-specific cultural transmission is

involved. Furthermore, directed scratches used by chimpanzees in the wild provide

evidence that (a) chimpanzees have an understanding of the intended meaning of

the gestures, and (b) signallers might be able to signal the action they want a

receiver to do. It is therefore possible that they constitute the first step towards

symbolic gestures.

Interestingly, although the most recent studies on gestural communication in apes

were inspired by the study of gestural communication in human children, there is

one intriguing difference in approaches to this topic: researchers investigating ges-

tural signals in apes include those gestures which incorporate the use of objects, for

instance, move (Pika et al., 2003), object shake (Liebal, 2007a; Liebal, 2007b; Pika et

al., 2003), present object (Liebal, 2007a), straw wave (Pika et al., 2003), wave object

(Pika et al., 2005b; Tomasello et al., 1985). Moreover, some of the gestures

described, incorporate repeated movements on objects or on the ape’s own body,

such as the gestures chest beat, body beat, slap ground and object drum (Pika et al.,

2003). In contrast, researchers working on gestures of human children focus mainly

on gestures that are performed in space (Bates et al., 1975; Capirci, Montanari &

Volterra, 1998; Nicoladis et al., 1999) and may only in specific cases include touch-

ing an object (e.g., pointing by touching the referent; Iverson et al., 1994). Research

on gestures in human children is therefore biased towards so-called ‘empty-handed’

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gestures (Petitto, 1988). Many studies exclude gestures that are performed on

objects or gestures with an object-referent in hand, denoting them as functional

object use play or meaningful action (e.g., Acredelo & Goodwyn, 1988; Goldin-

Meadow & Morford, 1990; Guidetti, 2002; Iverson & Goldin-Meadow, 2005).

However, Iverson et al. (1994) correctly noted that this exclusion procedure leads to

an underestimation of the production of gestures. They suggest that in order to

employ comparable criteria for communicative gestures, gestures incorporating

objects should be included if they appear to be truly communicative (which means

they have to be accompanied by eye contact, vocalization, or other clear evidence of

an effort to direct the attention of another person present in the room; Thal &

Tobias, 1992). Similarly, Capirci, Contaldo, Caselli & Volterra (2005: 162) note that

‘actions and gestures produced in a communicative context are not clearly separate

categories. Rather they should be considered a continuum and even adults can

produce gestures with an object in hand for communicative purposes.’

Overall, the crucial difference between gestures of apes and of pre- and just-

linguistic human children seems to be the obvious focusing on the function of

gestures. In their natural communication, apes mainly use imperative gestures to

communicate with their conspecifics, while all examples of declarative gesturing

are from apes interacting with their caretakers or from human-raised or language-

trained individuals (see also Leavens et al., 2004). Human children gesture for imper-

ative purposes but also, from very early on, for declarative purposes to direct the

attention of others to some third entity, simply for the sake of sharing interest in it

or commenting on it (Bates et al., 1975; Liszkowski et al., 2004), and later for

informative purposes (Liszkowski, 2005). These abilities seem to be unique for

human beings and might have triggered the onset of symbolic communication, i.e.,

language. It is therefore quite puzzling why only human beings comment on outside

entities simply to share experiences. One possibility is that this behaviour is linked

with the cognitive ability that enables humans to understand other persons as inten-

tional agents with whom they may share experience (Tomasello, Carpenter, Call,

Behne & Moll, 2005). This propensity derived from the need to create a new medium

for social bonding triggered by an increase of group size, superseding grooming as

a servicing tool for social relationships (Dunbar, 1996; Pika, in press). During groom-

ing the social relationships of (mainly) two individuals can be established and serv-

iced at the same time, but the medium of declarative gestures offers two key

features, which make communication in larger groups more efficient. First, it is pos-

sible to gesture to several people at the same time, thereby increasing the rate

at which signallers interact with recipients. Second, gesturing about third entities

allows the exchange of information about evolutionary urgent (e.g., predators,

food) and other relevant things in the world, thereby creating a wider network of

individuals and relevant facts than is possible for monkeys and apes.

CONCLUSION

Many human gestures are used functionally in ways very similar to language. They

are, in their essence, individually learned and intersubjectively shared social con-

ventions used to direct the attentional and mental states of others to outside

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entities referentially (Pika et al., 2005a). Apes also gesture on a regular basis in their

natural communication but use these communicative means mainly as effective

procedures in dyadic interactions to request actions from others. However, many

of these gestures are used intentionally and are clearly learned. Thus, this review

provides further support for the hypothesis that the gestural modality of our closest

living relatives might have been the crucial modality within which the evolutionary

precursors of symbolic communication evolved. Future studies, comparing the com-

municative skills of humans and apes in natural settings and the cognitive capaci-

ties that are thus demonstrated will, it is hoped, shed further light on the skills that

were available during the dawn of language.

ACKNOWLEDGEMENTS

I am grateful to J. Call, K. Liebal and M. Tomasello, who shared their data with me. I am

indebted to Dorothee Classen, who let me use her drawing of the directed scratch. For com-

ments on an earlier draft and lively discussions, I would like to thank Michèle Guidetti and

two anonymous reviewers. I was also inspired by valuable discussions with participants of the

Cradle of Language Conference in Stellenbosch, South Africa.

NOTES

1. See also the website for the Primate Gesture Center: http://www.primate-gesture-

center.eu

2. Auditory gestures generate sound while performed.

3. Defined in the next paragraph.

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ADDRESS FOR CORRESPONDENCE

Dr Simone Pika

University of Manchester, School of Psychological Sciences,

Coupland 1 Building, Oxford Road, Manchester, M13 9PL, UK

E: simone.pika@manchester.ac.uk

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Dec 2022
INT J PRIMATOL

Gestural communication is crucial for primates. However, little is known about how gestural repertoires emerge through development. We conducted behavioural observations on captive apes, including 18 siamangs ( Symphalangus syndactylus ), 16 Sumatran orangutans ( Pongo abelii ), and 19 chimpanzees ( Pan troglodytes ), to test different hypotheses for the emergence of gestures (i.e., Phylogenetic Ritualization, Ontogenetic Ritualization, Social Negotiation, and Social Transmission hypotheses). Our results showed little variation in individual gestural repertories, and only one idiosyncratic gesture. Moreover, across subjects (N = 53), repertoire size did not increase with age and social centrality. When comparing repertoires across all possible combinations of conspecifics, including apes in different groups (N=273) for the four groups of siamangs and the two of orangutans, repertoire similarity was higher in dyads of the same group than of different groups, but it also increased with more observational effort and lower age difference between group members. Finally, when comparing repertoires across all dyads of conspecifics in the same group (N = 260), we found no differences in repertoire similarity depending on dyadic relationship quality. Overall, these results provide support for the Phylogenetic Ritualization hypothesis, according to which individuals are endowed with complete gestural repertories from birth. These repertoires are largely similar across individuals and groups, although they may be partially refined through social experiences.

Shared semantics: Exploring the interface between human and chimpanzee gestural communication

Article

Full-text available

Feb 2024

Striking similarities across ape gestural repertoires suggest shared phylogenetic origins that likely provided a foundation for the emergence of language. We pilot a novel approach for exploring possible semantic universals across human and nonhuman ape species. In a forced‐choice task, n = 300 participants watched 10 chimpanzee gesture forms performed by a human and chose from responses that paralleled inferred meanings for chimpanzee gestures. Participants agreed on a single meaning for nine gesture forms; in six of these the agreed form‐meaning pair response(s) matched those established for chimpanzees. Such shared understanding suggests apes' (including humans') gesturing shares deep evolutionary origins.

Bodies at play: the role of intercorporeality and bodily affordances in coordinating social play in chimpanzees in the wild

Article

Full-text available

Jan 2024

The comparative approach is a crucial method to gain a better understanding of the behavior of living human and nonhuman animals to then draw informed inferences about the behavior of extinct ancestors. One focus has been on disentangling the puzzle of language evolution. Traditionally, studies have predominantly focused on intentionally produced signals in communicative interactions. However, in collaborative and highly dynamic interactions such as play, underlying intentionality is difficult to assess and often interactions are negotiated via body movements rather than signals. This “lack” of signals has led to this dynamic context being widely ignored in comparative studies. The aim of this paper is threefold: First, we will show how comparative research into communication can benefit from taking the intentionality-agnostic standpoint used in conversation analysis. Second, we will introduce the concepts of ‘intercorporeality’ and ‘bodily affordance’, and show how they can be applied to the analysis of communicative interactions of nonhuman animals. Third, we will use these concepts to investigate how chimpanzees (Pan troglodytes) initiate, end, and maintain ‘contact social play’. Our results showed that bodily affordances are able to capture elements of interactions that more traditional approaches failed to describe. Participants made use of bodily affordances to achieve coordinated engagement in contact social play. Additionally, these interactions could display a sequential organization by which one ‘move’ by a chimpanzee was responded to with an aligning ‘move’, which allowed for the co-construction of the activity underway. Overall, the present approach innovates on three fronts: First, it allows for the analysis of interactions that are often ignored because they do not fulfil criteria of intentionality, and/or consist of purely body movements. Second, adopting concepts from research on human interaction enables a better comparison of communicative interactions in other animal species without a too narrow focus on intentional signaling only. Third, adopting a stance from interaction research that highlights how practical action can also be communicative, our results show that chimpanzees can communicate through their embodied actions as well as through signaling. With this first step, we hope to inspire new research into dynamic day-to-day interactions involving both “traditional” signals and embodied actions, which, in turn, can provide insights into evolutionary precursors of human language.

Wild and captive immature orangutans differ in their non-vocal communication with others, but not with their mothers

Article

Full-text available

Jan 2024
BEHAV ECOL SOCIOBIOL

In many group-living species, individuals are required to flexibly modify their communicative behaviour in response to current social challenges. To unravel whether sociality and communication systems co-evolve, research efforts have often targeted the links between social organisation and communicative repertoires. However, it is still unclear which social or interactional factors directly predict communicative complexity. To address this issue, we studied wild and zoo-housed immature orangutans of two species to assess the impact of the socio-ecological setting on the production of non-vocal signal repertoires. Specifically, we compared repertoire size, dyadic repertoire similarity, and number of social goals (i.e. observer’s estimate of the signaller’s intended interaction outcome) for communicative interactions with mothers versus other conspecifics, controlling for critical individual and environmental factors. In this small sample of immature orangutans, wild-captive contrasts were statistically significant only for other-directed repertoires, but not for mother-directed repertoires, and not for the number of social goals that immatures communicated towards. While the repertoires of individuals living in the same research setting were more similar than those living in contrasting settings, this difference was most pronounced for other-directed repertoires of the less socially tolerant orangutan species. These results suggest that the boosted interactional opportunities in captivity rather than mere differences in environmental affordances or communicative needs drive the wild-captive contrast in orangutan communicative repertoires. Overall, this fine-grained analysis of repertoires further underscores that not only a species’ social organisation but also the targeted audience may have a profound impact on communicative behaviour. Significance statement Navigating a dynamic social environment often requires flexible signal use. While it has repeatedly been shown that the social organisation and structure of species predict the complexity of their communication systems, the mechanisms underlying these relationships are largely unknown. Because targeted studies to assess this issue in great apes are difficult, we take an alternative approach here: we compare the same species living in the wild and in artificial habitats in captivity. This contrast allows a direct test of how repertoires respond to the relevant difference in socio-ecological conditions. Our results show that the diversity of interaction partners (i.e. social opportunities), but not the diversity of social goals (i.e. possible interaction outcomes) or the broader physical opportunities (i.e. safe ground use), predict the size and consistency of wild and captive signalling repertoires.

Chimpanzees communicate to coordinate a cultural practice

Article

Full-text available

Jan 2023

Human culture thrives by virtue of communication, yet whether communication plays an influential role in the cultural lives of other animals remains understudied. Here, we investigated whether chimpanzees use communication to engage in a cultural practice by analysing grooming handclasp (GHC) interactions-a socio-cultural behaviour requiring interindividual coordination for successful execution. Previous accounts attributed GHC initiations to behavioural shaping, whereby the initiator physically moulds the partner's arm into the desired GHC posture. Using frame-by-frame analysis and matched-control methodology, we find that chimpanzees do not only shape their partner's posture (22%), but also use gestural communication to initiate GHC (44%), which requires an active and synchronized response from the partner. Moreover, in a third (34%) of the GHC initiations, the requisite coordination was achieved by seemingly effortless synchrony. Lastly, using a longitudinal approach, we find that for GHC initiations, communication occurs more frequently than shaping in experienced dyads and less in mother-offspring dyads. These findings are consistent with ontogen-etic ritualization, thereby reflecting first documentation of chimpanzees communicating to coordinate a cultural practice. We conclude that chimpanzees show interactional flexibility in the socio-cultural domain, opening the possibility that the interplay between communication and culture is rooted in our deep evolutionary history.

Neuroanatomical correlates of individual differences in the object choice task in chimpanzees (Pan troglodytes)

Article

Full-text available

Nov 2022

Declarative and imperative joint attention or joint engagement are important milestones in human infant development. These have been shown to be a significant predictor of later language development and are impaired in some individuals with, or at risk for, a diagnosis of autism spectrum disorder. Comparatively, while chimpanzees and other great apes have been reported to engage in imperative joint attention, evidence of declarative joint attention remains unclear based on existing studies. Some have suggested that differences in methods of assessing joint attention may have an influence on performance in nonhuman primates. Here, we report data on a measure of receptive joint attention (object choice task) in a sample of captive chimpanzees. Chimpanzees, as a group, performed significantly better than chance. By contrast, when considering individual performance, there was no significant difference in the number of those who passed and those who failed. Using quantitative genetic analyses, we found that performance on the object choice task was not significantly heritable nor were there any significant effects of sex, rearing history, or colony. Lastly, we found significant differences in gray matter covariation, between those who passed or failed the task. Those who passed contributed more to gray matter covariation in several brain regions within the social brain network, consistent with hypotheses regarding the importance of these regions in human and nonhuman primate social cognition.

Social tolerance and interactional opportunities as drivers of gestural redoings in orang-utans

Article

Full-text available

Jul 2022

Communicative repair is a fundamental and universal element of interactive language use. It has been suggested that the persistence and elaboration after communicative breakdown in nonhuman primates constitute two evolutionary building blocks of this capacity, but the conditions favouring it are poorly understood. Because zoo-housed individuals of some species are more social and more terrestrial than in the wild, they should be more likely to show gestural redoings (i.e. both repetition and elaboration) after communicative failure in the coordination of their joint activities. Using a large comparative sample of wild and zoo-housed orang-utans of two different species, we could confirm this prediction for elaboration, the more flexible form of redoings. Specifically, results showed that gestural redoings in general were best predicted by the specific social action context (i.e. social play) and interaction dyad (i.e. beyond mother–offspring), although they were least frequent in captive Bornean orang-utans. For gestural elaboration, we found the expected differences between captive and wild research settings in Borneans, but not in Sumatrans (the more socially tolerant species). Moreover, we found that the effectiveness of elaboration in eliciting responses was higher in Sumatrans, especially the captive ones, whereas effectiveness of mere repetition was influenced by neither species nor setting. We conclude that the socio-ecological environment plays a central role in the emergence of communicative repair strategies in great apes. This article is part of the theme issue ‘Revisiting the human ‘interaction engine’: comparative approaches to social action coordination’.

Individual variation and plasticity in the infant-directed communication of orang-utan mothers

Article

Full-text available

May 2022

Between-individual variation in behavioural expression, such as social responsiveness, has been shown to have important eco-evolutionary consequences. However, most comparative research on non-human primate communication has focused on species- or population-level variation, while among- and within-individual variation has been largely ignored or considered as noise. Here, we apply a behavioural reaction norm framework to repeated observations of mother–offspring interactions in wild and zoo-housed orang-utans ( Pongo abelii, P. pygmaeus ) to tease apart variation on the individual level from population-level and species-level differences. Our results showed that mothers not only differed in the composition of their infant-directed gestural repertoires, but also in communicative tactics, such as gestural redoings (i.e. persistence) and responsiveness to infants' requests. These differences remained after controlling for essential moderators, including species, setting, parity and infant age. Importantly, mothers differed in how they adjusted their behaviour across social contexts, making a strong case for investigating within-individual variation. Our findings highlight that partitioning behavioural variation into its within-individual, between-individual and environmental sources allows us to estimate the extent of plastic responses to the immediate environment in great ape communication.

Six-month-old infants’ communication in a comparative perspective: Do maternal attention and interaction matter?

Article

Feb 2023
J EXP CHILD PSYCHOL

Developmental precursors of the prelinguistic transition from gestures to word use can be found in the early pragmatic usage of auditory and visual signals across contexts. This study examined whether 6-month-old infants are capable of attention-sensitive communication with their mother, that is, adjusting the sensory modality of their communicative signals to their mother’s attention. Proxies of maternal attention implemented in experimental conditions were the mother’s visual attention (attentive/inattentive), interaction directed at the infant (interactive/non-interactive), and distance (far/close). The infants’ signals were coded as either visual or auditory, following an ethological coding. Infants adjusted the sensory modality of their communicative signals mostly to maternal interaction. More auditory signals were produced when the mother was non-interactive than when she was interactive. Interactive conditions were characterized by higher rates of visual signaling and of gaze-coordinated non-vocal oral sounds. The more time infants spent looking at their attentive mother, the more they produced auditory signals, specifically non-vocal oral sounds. These findings are discussed within the articulated frameworks of evolutionary developmental psychology and early pragmatics. Temporary download link: https://authors.elsevier.com/a/1gevB51Y-PtdN

Communication gestuelle et multimodale chez les mangabeys à collier (Cercocebus torquatus)

Thesis

Full-text available

Dec 2020

Juliette Aychet

Ce travail s’inscrit dans l’étude des origines évolutives du langage, par la recherche de propriétés langagières dans la communication gestuelle et multimodale de primates cercopithécidés en captivité, les mangabeys à collier. Par une double approche observationnelle et expérimentale, nous avons montré que les gestes des mangabeys remplissent les critères de définition d’une communication intentionnelle, et peuvent être produits de manière flexible dans différents contextes. Nos observations fournissent également de premiers éléments en faveur d’une intentionnalité des expressions faciales des cercopithécidés, souvent considérées comme de simples indices d’état émotionnel. Cette propriété sociocognitive langagière pourrait ainsi être plus ancienne que ce que nous pensions dans l’histoire évolutive des primates, et être héritée de la communication gestuelle des ancêtres des catarrhiniens, il y a environ 29 millions d’années. De plus, nous avons mis en évidence un effet significatif du contexte interactionnel sur la latéralité gestuelle des mangabeys, suggérant une importance particulière de facteurs sociaux dans l’émergence d’une spécialisation hémisphérique pour la communication intentionnelle, dont le langage humain. Enfin, par une méthode originale, reposant sur des analyses de séquences et de réseau, nous avons décrit la communication multimodale et multicomposante des mangabeys à collier, et montré qu’ils combinent de manière flexible différents types et modalités de signaux en fonction du contexte et de facteurs sociodémographiques. Nos résultats soulignent l’importance d’une approche multimodale pour comprendre la complexité de la communication des primates, et apportent de premier éléments de compréhension sur la fonction des combinaisons de signaux. De futures comparaisons à d’autres espèces et dans différents environnements pourraient permettre d’affiner nos connaissances quant aux possibles contraintes évolutives ayant favorisé une telle complexité de la communication des primates humains et non-humains.

Indexical and Referential Pointing in Chimpanzees (Pan troglodytes )

Article

Full-text available

Dec 1996

The spontaneous index finger and other referential pointing in 3 adult, laboratory chimpanzees (Pan troglodytes) who have not received language training is reported. Of 256 total observed points, 254 were emitted in the presence of a human to objects in the environment; therefore, the points were communicative. Indicators of intentional communication used by the subjects included attention-getting behaviors, gaze alternation, and persistence until reward. Thus, pointing by these chimpanzees was intentionally communicative. These data imply that perspective-taking and referential communication are generalized hominoid traits, given appropriate eliciting contexts. Index finger pointing was more frequent with the subjects' dominant hands. This study refutes claims that indexical or referential pointing is species-unique to humans or dependent on linguistic competence or explicit training.

Production and Comprehension of Referential Pointing by Orangutans (Pongo pygmaeus )

Article

Full-text available

Dec 1994

We report 3 studies of the referential pointing of 2 orangutans (Pongo pygmaeus). Chantek was raised in an enculturated environment; Puti, raised in a nursery, had a more typical captive life. In Experiment 1, flexibility of pointing behavior was investigated by requiring subjects to point in novel circumstances (for an out-of-sight tool, not food). In Experiment 2, we investigated the orangutans' comprehension of the significance of a human point in helping them to locate food. In Experiment 3, we investigated whether these pointing subjects comprehended that a human recipient must be looking for the point to achieve its attention-directing goal. In all experiments the enculturated orangutan showed better understanding of pointing than the captive orangutan. This finding is consistent with recent studies that have found differences in the cognitive and social–cognitive abilities of apes that have had different types of experience with humans.

The development of spontaneous gestural communication in a group of zoo-living lowland gorillas

Chapter

Full-text available

Aug 1999

Research on the mental abilities of chimpanzees and bonobos has been widely celebrated and used in reconstructions of human evolution. In contrast, less attention has been paid to the abilities of gorillas and orangutans. This 1999 volume aims to help complete the picture of hominoid cognition by bringing together the work on gorillas and orangutans and setting it in comparative perspective. The introductory chapters set the evolutionary context for comparing cognition in gorillas and orangutans to that of chimpanzees, bonobos and humans. The remaining chapters focus primarily on the kinds and levels of intelligence displayed by orangutans and gorillas compared to other great apes, including performances in the classic domains of tool use and tool making, imitation, self-awareness, social communication and symbol use. All those wanting more information on the mental abilities of these sometimes neglected, but important primates will find this book a treasure trove.

The Mirror System, Imitation, and the Evolution of Language

Chapter

Jun 2002

Michael A Arbib

An interdisciplinary overview of current research on imitation in animals and artifacts. The effort to explain the imitative abilities of humans and other animals draws on fields as diverse as animal behavior, artificial intelligence, computer science, comparative psychology, neuroscience, primatology, and linguistics. This volume represents a first step toward integrating research from those studying imitation in humans and other animals, and those studying imitation through the construction of computer software and robots. Imitation is of particular importance in enabling robotic or software agents to share skills without the intervention of a programmer and in the more general context of interaction and collaboration between software agents and humans. Imitation provides a way for the agent—whether biological or artificial—to establish a "social relationship" and learn about the demonstrator's actions, in order to include them in its own behavioral repertoire. Building robots and software agents that can imitate other artificial or human agents in an appropriate way involves complex problems of perception, experience, context, and action, solved in nature in various ways by animals that imitate. Bradford Books imprint

From Hand to Mouth: The Origins of Language

Book

Jan 2002

Michael C. Corballis

Gesture and the Nature of Language

Book

Mar 1995

This book proposes a radical alternative to dominant views of the evolution of language, and in particular the origins of syntax. The authors argue that manual and vocal communication developed in parallel, and that the basic elements of syntax are intrinsic to gesture. They draw on evidence from areas such as primatology, anthropology, and linguistics, to present a groundbreaking account of the notion that language emerged through visible bodily action. They go on to examine the implications of their findings for linguistic theory and theories of the biological evolution of the capacity for language. Written in a clear and accessible style, Gesture and the Nature of Language will be indispensable reading for all those interested in the origins of language.

Animal Vocal Communication: A New Approach

Book

Apr 1998

This book will be a landmark text for all those interested in animal communication. Animal Vocal Communication explicitly avoids human-centred concepts and approaches and links communication to fundamental biological processes instead. It offers a conceptual framework - assessment/management - that allows us to integrate detailed studies of communication with an understanding of evolutionary perspectives. Self-interested assessment is placed on par with the signal production (management) side of communication, and communication is viewed as reflecting regulatory processes. Signals are used to manage the behaviour of others by exploiting their active assessment. The authors contend that it is this interplay between management and assessment that results in the functioning and evolution of animal communication; it is what communicative behaviour accomplishes that is important, not what information is conveyed.

The mentalities of gorillas and orangutans in phylogenetic perspective

Chapter

Aug 1999

Levels of imitation and cognitive mechanisms in orangutans

Chapter

Aug 1999

Joseph Call

How Monkeys See the World: Inside the Mind of Another Species

Book

Jan 1990

Gestures of apes and pre-linguistic human children: Similar or different?

Abstract and Figures

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