Great ape gestures: intentional communication with a rich set of innate signals

Great apes give gestures deliberately and voluntarily, in order to influence particular target audiences, whose direction of attention they take into account when choosing which type of gesture to use. These facts make the study of ape gesture directly relevant to understanding the evolutionary precursors of human language; here we present an assessment of ape gesture from that perspective, focusing on the work of the “St Andrews Group” of researchers. Intended meanings of ape gestures are relatively few and simple. As with human words, ape gestures often have several distinct meanings, which are effectively disambiguated by behavioural context. Compared to the signalling of most other animals, great ape gestural repertoires are large. Because of this, and the relatively small number of intended meanings they achieve, ape gestures are redundant, with extensive overlaps in meaning. The great majority of gestures are innate, in the sense that the species’ biological inheritance includes the potential to develop each gestural form and use it for a specific range of purposes. Moreover, the phylogenetic origin of many gestures is relatively old, since gestures are extensively shared between different genera in the great ape family. Acquisition of an adult repertoire is a process of first exploring the innate species potential for many gestures and then gradual restriction to a final (active) repertoire that is much smaller. No evidence of syntactic structure has yet been detected.     

Semantics of primate gestures: intentional meanings of orangutan gestures

Great ape gesture has become a research topic of intense interest, because its intentionality and flexibility suggest strong parallels to human communication. Yet the fundamental question of whether an animal species’ gestures carry specific meanings has hardly been addressed. We set out a systematic approach to studying intentional meaning in the gestural communication of non-humans and apply it to a sample of orangutan gestures. We propose that analysis of meaning should be limited to gestures for which (1) there is strong evidence for intentional production and (2) the recipient’s final reaction matches the presumed goal of the signaller, as determined independently. This produces a set of “successful” instances of gesture use, which we describe as having goal–outcome matches. In this study, 28 orangutans in three European zoos were observed for 9 months. We distinguished 64 gestures on structural grounds, 40 of which had frequent goal–outcome matches and could therefore be analysed for meaning. These 40 gestures were used predictably to achieve one of 6 social goals: to initiate an affiliative interaction (contact, grooming, or play), request objects, share objects, instigate co-locomotion, cause the partner to move back, or stop an action. Twenty-nine of these gestures were used consistently with a single meaning. We tested our analysis of gesture meaning by examining what gesturers did when the response to their gesture did not match the gesture’s meaning. Subsequent actions of the gesturer were consistent with our assignments of meaning to gestures. We suggest that, despite their contextual flexibility, orangutan gestures are made with the expectation of specific behavioural responses and thus have intentional meanings as well as functional consequences.     

Thirty years of great ape gestures

Animal Cognition - We and our colleagues have been doing studies of great ape gestural communication for more than 30 years. Here we attempt to spell out what we have learned. Some aspects...     

How iconic gestures enhance communication: an ERP study

EEG was recorded as adults watched short segments of spontaneous discourse in which the speaker's gestures and utterances contained complementary information. Videos were followed by one of four types of picture probes: cross-modal related probes were congruent with both speech and gestures; speech-only related probes were congruent with information in the speech, but not the gesture; and two sorts of unrelated probes were created by pairing each related probe with a different discourse prime. Event-related potentials (ERPs) elicited by picture probes were measured within the time windows of the N300 (250-350 ms post-stimulus) and N400 (350-550 ms post-stimulus). Cross-modal related probes elicited smaller N300 and N400 than speech-only related ones, indicating that pictures were easier to interpret when they corresponded with gestures. N300 and N400 effects were not due to differences in the visual complexity of each probe type, since the same cross-modal and speech-only picture probes elicited N300 and N400 with similar amplitudes when they appeared as unrelated items. These findings extend previous research on gesture comprehension by revealing how iconic co-speech gestures modulate conceptualization, enabling listeners to better represent visuo-spatial aspects of the speaker's meaning.     

Embodied communication: Speakers’ gestures affect listeners’ actions

We explored how speakers and listeners use hand gestures as a source of perceptual-motor information during naturalistic communication. After solving the Tower of Hanoi task either with real objects or on a computer, speakers explained the task to listeners. Speakers’ hand gestures, but not their speech, reflected properties of the particular objects and the actions that they had previously used to solve the task. Speakers who solved the problem with real objects used more grasping handshapes and produced more curved trajectories during the explanation. Listeners who observed explanations from speakers who had previously solved the problem with real objects subsequently treated computer objects more like real objects; their mouse trajectories revealed that they lifted the objects in conjunction with moving them sideways, and this behavior was related to the particular gestures that were observed. These findings demonstrate that hand gestures are a reliable source of perceptual-motor information during human communication.     

Mind knowledge in infancy: The emergence of intentional communication

When and how infants and young children start to understand that persons are entities different from ‘non-persons ’ is the central issue addressed in this paper. A critical examination is presented of empirical research inspired by the ‘theory of mind ’ approach and relative to the knowledge about the mind exhibited by pre-school children (2–5 years of age). In considering what kind of psychological knowledge pre-linguistic children may acquire, it is argued that the most significant developmental phenomenon is the grasp of the concept of intentional communication, as distinct from both agency and instrumentality. Intentional communication, so defined, implies the capacity to represent and influence the other person's attentional state about aspects of the world, and at the same time to represent the other person as capable of understanding one's communicative intentions.     

A gestural repertoire of 1- to 2-year-old human children: in search of the ape gestures

Animal Cognition - When we compare human gestures to those of other apes, it looks at first like there is nothing much to compare at all. In adult humans, gestures are thought to be a window into...     

Form and function in early communication: language and pointing gestures

Pointing gestures of verbally advanced 2-year-olds were contrasted with those of less advanced peers, in order to examine the relationships of gesture to language during the acquisition of each. Hypotheses regarding the replacement of gestural functions by speech as verbal skills improve, regarding developmental correspondences between the two communicative domains, and regarding the independence of language acquisition from nonverbal developments were drawn from evolutionary, structuralist, and nativist viewpoints, respectively. Both formal and functional aspects of each communicative skill were measured, and were shown to be largely unrelated, particularly in the gestural domain. No evidence that language replaced gesture for communication in ontogeny was obtained. Correspondences between gesture and language occurred only between functional aspects of each, and the independence of developing language from gestural advances was suggested by the findings.     

The ontogeny of intentional communication in chimpanzees in the wild

The onset of intentional communication in children's first year of life represents a major milestone in human cognitive development. Similarly, it is well established that our closest living relatives, the great apes, communicate with signals characterized by at least first‐order intentionality. Despite the well‐documented influence of developmental experiences on socio‐cognitive abilities in apes, the developmental trajectory of intentional signal use as well as effects of social exposure remain poorly understood under naturalistic conditions. Here, we addressed these issues by studying the ontogeny of intentional communication in chimpanzee infants of two subspecies (Pan troglodytes schweinfurthii/verus) and communities living in their natural environments. Overall, we found that gestures and bimodal signal combinations were most commonly accompanied by markers of intentional communication: audience checking, persistence to the goal, and sensitivity to recipient’s attentional state. Within individuals, the proportion of communicative behaviours associated with goal persistence and sensitivity to attention increased with age. Cross‐sectional comparisons between infants revealed an age effect on the use of audience checking. Context, interaction partner and site affiliation affected the production of specific markers irrespective of infants' age. The present study provided hitherto undocumented evidence for the development of three important markers of intentional communication in great apes. Moreover, our results suggest that social exposure impacts early intentional signal use.     

Correspondence effects with manual gestures and postures: a study of imitation

In this study, the authors applied methods and theories from research of stimulus-response compatibility (SRC) to action imitation. In 6 experiments, they adopted the logic of the Simon paradigm (B. Hommel & W. Prinz, 1996) to explore interference between task-relevant symbolic stimulus features (color) and task-irrelevant iconic stimulus features (2 hand gestures and 2 postures). The same 2 hand gestures served as responses. Pronounced correspondence effects for both gestures and postures showed up throughout. In line with theories of SRC, the authors account for these correspondence effects in terms of overlap arising between stimulus and response features in a common representational domain. As a specific extension of this approach, they propose 2 functionally independent mechanisms: One operates movement-based when dynamic information is provided, and the other operates state-based with static postures as stimuli. Implications for theories of both SRC and action imitation are discussed.     

The mnemonic effect of speech gestures: Pantomimic and non-pantomimic gestures compared

Abstract

A video-taped model presented subjects with sets of sentences to be free-recalled. under three presentation conditions: (1) accompanied by pantomimic gestures; (2) accompanied by non-pantomimic gestures; and (3) no gestures present. When the sentences formed a narrative, the gestures did not affect recall. When the sentences were unconnected, recall was higher for the gestured than for tbe non-gestured sentences. The pantomimic and non-pantomimic gestures showed about the same mnemonic effect. The subjects were given a second test, either recall-cued by the gestures, or else free recall of the gestured Sentences only. The pantomimic conditions were superior to the non-pantomimic conditions in both these tests. Possible explanations for the mnemonic effects of the gestures are discussed.     

The ‘circumstances’ of gestures: Proto-interrogatives and private gestures

The later Wittgenstein's emphasis on the social usage of language has been very influential in psychology, particularly in language acquisition research. This move toward a pragmatic position should also be applied to gestures in pre-linguistic children and to objects in the everyday contexts of use. The shared ‘forms of life’ presupposed by language involve pre-linguistic gestures and material ‘things’.Research on early communication has focused on proto-declarative and proto-imperative gestures. I extend this focus and propose further types of gestures: ‘proto-interrogatives’ - in which children “ask” for help or regulation from adults, and three types of ‘private gestures’ - ostensive, indexical and symbolic - in which children regulate their own behaviour. This diversity of gestures becomes apparent when objects are taken seriously. Wittgenstein's ‘language-games’ necessarily apply to games with objects and gestures as well: social meaning in all cases is emergent within the context of these ‘sign games’ and ‘circumstances.’     

The semantic specificity of gestures when verbal communication is not possible: The case of emergency evacuation

The aim of the present study was to examine the comprehension of gesture in a situation in which the communicator cannot (or can only with difficulty) use verbal communication. Based on theoretical considerations, we expected to obtain higher semantic comprehension for emblems (gestures with a direct verbal definition or translation that is well known by all members of a group, or culture) compared to illustrators (gestures regarded as spontaneous and idiosyncratic and that do not have a conventional definition). Based on the extant literature, we predicted higher semantic specificity associated with arbitrarily coded and iconically coded emblems compared to intrinsically coded illustrators. Using a scenario of emergency evacuation, we tested the difference in semantic specificity between different categories of gestures. 138 participants saw 10 videos each illustrating a gesture performed by a firefighter. They were requested to imagine themselves in a dangerous situation and to report the meaning associated with each gesture. The results showed that intrinsically coded illustrators were more successfully understood than arbitrarily coded emblems, probably because the meaning of intrinsically coded illustrators is immediately comprehensible without recourse to symbolic interpretation. Furthermore, there was no significant difference between the comprehension of iconically coded emblems and that of both arbitrarily coded emblems and intrinsically coded illustrators. It seems that the difference between the latter two types of gestures was supported by their difference in semantic specificity, although in a direction opposite to that predicted. These results are in line with those of Hadar and Pinchas‐Zamir (2004), which showed that iconic gestures have higher semantic specificity than conventional gestures.     

The intentional spring: a strategy for modeling systems that learn to perform intentional acts

In motor task learning by instruction, the instructor's skill and intention, which, initially, are extrinsic constraints on the learner's perceiving and acting, eventually become internalized as intrinsic constraints by the learner. How is this process to be described formally? This process takes place via a forcing function that acts both as an anticipatory (informing) influence and a hereditary (controlling) influence. A mathematical strategy is suggested by which such intentions and skills might be dynamically learned. A hypothetical task is discussed in which a blindfolded learner is motorically instructed to pull a spring to a specific target in a specific manner. The modeling strategy involves generalizing Hooke's law to the coupled instructor-spring-Learner system. Specifically, dual Volterra functions express the anticipatory and hereditary influences passed via an instructor-controlled forcing function on the shared spring. Boundary conditions (task goals) on the instructor-spring system, construed as a mathematical (self-adjoint) operator, are passed to the learner-spring system. Psychological interpretation is given to the involved mathematical operations that are passed, and mathematical (Hilbert-Schmidt's and Green's function) techniques are used to account for the release of the boundary conditions by the instructor and their absorption by the learner, and an appropriate change of their power spectra.     

Functionally referential and intentional communication in the domestic dog: effects of spatial and social contexts

In apes, four criteria are set to explore referential and intentional communication: (1) successive visual orienting between a partner and distant targets, (2) the presence of apparent attention-getting behaviours, (3) the requirement of an audience to exhibit the behaviours, and (4) the influence of the direction of attention of an observer on the behaviours. The present study aimed at identifying these criteria in behaviours used by dogs in communicative episodes with their owner when their toy is out of reach, i.e. gaze at a hidden target or at the owner, gaze alternation between a hidden target and the owner, vocalisations and contacts. In this study, an additional variable was analysed: the position of the dog in relation to the location of the target. Dogs witnessed the hiding of a favourite toy, in a place where they could not get access to. We analysed how dogs engaged in communicative deictic behaviours in the presence of their owner; four heights of the target were tested. To control for the motivational effects of the toy on the dogs’ behaviour and for the referential nature of the behaviours, observations were staged where only the toy or only the owner was present, for one of the four heights. The results show that gazing at the container and gaze alternation were used as functionally referential and intentional communicative behaviours. Behavioural patterns of dog position, the new variable, fulfilled the operational criteria for functionally referential behaviour and a subset of operational criteria for intentional communication: the dogs used their own position as a local enhancement signal. Finally, our results suggest that the dogs gazed at their owner at optimal locations in the experimental area, with respect to the target height and their owner’s (or their own) line of gaze.     

Shared minds: How mothers and infants co-construct early patterns of choice within intentional communication partnerships

The qualitative research method of case study inquiry is employed to investigate different patterns observed in early communicative interactions between two infants and their mothers. These mothers and babies were similar in significant ways: Both mothers were observed to be competent, well-functioning adults and reported no communicative or parenting dysfunction: both infants were evaluated as developing normally in terms of their cognitive level and acquisition of communication behaviors. However, a difference was observed between the dyads in their effectiveness in contributing to the infants' development as intentional communicators. The extent to which an infant and mother “share minds” is proposed as accounting for the observed difference. This phenomenon of “shared minds” is examined by observing the process of choice co-construction engaged in by mothers and infants during communication. It is concluded that characteristics of these early co-constructions influence the way in which the young child begins to act with intention and to interpret him- or herself and others as intentional communicative beings. © 1997 Michigan Association for Infant Mental Health     

A cross-cultural study of the communication of extra-verbal meaning by gestures(1)

English and Italian encoders were asked to communicate two-dimensional shapes to decoders of their own culture, with and without the use of hand gestures, for materials of high and low verbal codability. The decoders drew what they thought the shapes were and these were rated by English and Italian judges, for similarity to the originals. Higher accuracy scores were obtained by both the English and the Italians, when gestures were allowed, for materials of both high and low codability; but the effect of using gestures was greater for materials of low codability. Improvement in performance when gestures were allowed was greater for the Italians than for the English for both levels of codability. An analysis of the recorded verbal utterances has shown that the detriment in communication accuracy with the elimination of gestures cannot be attributed to disruption of speech performance; rather, changes in speech content occur indicating an increased reliance on verbal means of conveying spatial information. Nevertheless, gestures convey this kind of semantic information more accurately and evidence is provided for the gestures of the Italians communicating this information more effectively than those of the English.     

The gestures of a gorilla: language acquisition in another pongid

A female lowland gorilla, Koko, has been engaged in an ongoing language program since July 1972 when she was 1 year old. During the first 30 months of training she acquired a vocabulary of 100 words in American Sign Language which she spontaneously combined into meaningful and often novel statements of up to 11 signs in length. The gorilla is using a rapidly expanding vocabulary of signs to express semantic and possibly grammatical relations similar to those expressed by human children in the early stages of language acquisition. Patterns of generalization, gradual increase in mean length of utterance, and innovative use of gestural language are discussed in relation to data available on children and chimpanzees.     

Embodying gestures: The Social Orienting Model and the study of early gestures in autism

Autistic spectrum disorders impair the ability to interact socially. Detecting and understanding their onset is not only an empirical enterprise, but also a theoretical one, often linked to studies on intersubjectivity. Different theoretical perspectives have been elaborated in the past to account for the deficit. The main purpose of this paper is to reinforce and offer empirical grounding to a recent approach, termed Social Orienting Model, by presenting the main theoretical approaches to autism and contrasting them to this view, as well as considering its possible effect on empirical research, focusing on current literature analyzing gestures in children with autism.