Should I stay or should I go? Initiation of joint travel in mother–infant dyads of two chimpanzee communities in the wild

It is well established that great apes communicate via intentionally produced, elaborate and flexible gestural means. Yet relatively little is known about the most fundamental steps into this communicative endeavour—communicative exchanges of mother–infant dyads and gestural acquisition; perhaps because the majority of studies concerned captive groups and single communities in the wild only. Here, we report the first systematic, quantitative comparison of communicative interactions of mother–infant dyads in two communities of wild chimpanzees by focusing on a single communicative function: initiation of carries for joint travel. Over 156 days of observation, we recorded 442 actions, 599 cases of intentional gesture production, 51 multi-modal combinations and 80 vocalisations in the Kanyawara community, Kibale National Park, Uganda, and the Taï South community, Taï National Park, Côte d’Ivoire. Our results showed that (1) mothers and infants differed concerning the signal frequency and modality employed to initiate joint travel, (2) concordance rates of mothers’ gestural production were relatively low within but also between communities, (3) infant communicative development is characterised by a shift from mainly vocal to gestural means, and (4) chimpanzee mothers adjusted their signals to the communicative level of their infants. Since neither genetic channelling nor ontogenetic ritualization explains our results satisfactorily, we propose a revised theory of gestural acquisition, social negotiation, in which gestures are the output of social shaping, shared understanding and mutual construction in real time by both interactants.     

Gestural communication of the gorilla (Gorilla gorilla): repertoire, intentionality and possible origins

Social groups of gorillas were observed in three captive facilities and one African field site. Cases of potential gesture use, totalling 9,540, were filtered by strict criteria for intentionality, giving a corpus of 5,250 instances of intentional gesture use. This indicated a repertoire of 102 gesture types. Most repertoire differences between individuals and sites were explicable as a consequence of environmental affordances and sampling effects: overall gesture frequency was a good predictor of universality of occurrence. Only one gesture was idiosyncratic to a single individual, and was given only to humans. Indications of cultural learning were few, though not absent. Six gestures appeared to be traditions within single social groups, but overall concordance in repertoires was almost as high between as within social groups. No support was found for the ontogenetic ritualization hypothesis as the chief means of acquisition of gestures. Many gestures whose form ruled out such an origin, i.e. gestures derived from species-typical displays, were used as intentionally and almost as flexibly as gestures whose form was consistent with learning by ritualization. When using both classes of gesture, gorillas paid specific attention to the attentional state of their audience. Thus, it would be unwarranted to divide ape gestural repertoires into ‘innate, species-typical, inflexible reactions’ and ‘individually learned, intentional, flexible communication’. We conclude that gorilla gestural communication is based on a species-typical repertoire, like those of most other mammalian species but very much larger. Gorilla gestures are not, however, inflexible signals but are employed for intentional communication to specific individuals.     

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.     

Maternal gestures with 20-month-old infants in two contexts

Speech directed towards young children ("motherese") is subject to consistent systematic modifications. Recent research suggests that gesture directed towards young children is similarly modified (gesturese). It has been suggested that gesturese supports speech, therefore scaffolding communicative development (the facilitative interactional theory). Alternatively, maternal gestural modification may be a consequence of the semantic simplicity of interaction with infants (the interactional artefact theory). The gesture patterns of 12 English mothers were observed with their 20-month-old infants while engaged in two tasks, free play and a counting task, designed to differentially tap into scaffolding. Gestures accounted for 29% of total maternal communicative behaviour. English mothers employed mainly concrete deictic gestures (e.g. pointing) that supported speech by disambiguating and emphasizing the verbal utterance. Maternal gesture rate and informational gesture-speech relationship were consistent across tasks, supporting the interactional artefact theory. This distinctive pattern of gesture use for the English mothers was similar to that reported for American and Italian mothers, providing support for universality. Child-directed gestures are not redundant in relation to child-directed speech but rather both are used by mothers to support their communicative acts with infants.     

Beside the point: Mothers’ head nodding and shaking gestures during parent–child play

Understanding the context for children's social learning and language acquisition requires consideration of caregivers’ multi-modal (speech, gesture) messages. Though young children can interpret both manual and head gestures, little research has examined the communicative input that children receive via parents’ head gestures. We longitudinally examined the frequency and communicative functions of mothers’ head nodding and head shaking gestures during laboratory play sessions for 32 mother–child dyads, when the children were 14, 20, and 30 months of age. The majority of mothers produced head nods more frequently than head shakes. Both gestures contributed to mothers’ verbal attempts at behavior regulation and dialog. Mothers’ head nods primarily conveyed agreement with, and attentiveness to, children's utterances, and accompanied affirmative statements and yes/no questions. Mothers’ head shakes primarily conveyed prohibitions and statements with negations. Changes over time appeared to reflect corresponding developmental changes in social and communicative dimensions of caregiver–child interaction. Directions for future research are discussed regarding the role of head gesture input in socialization and in supporting language development.     

The repertoire and intentionality of gestural communication in wild chimpanzees

A growing body of evidence suggests that human language may have emerged primarily in the gestural rather than vocal domain, and that studying gestural communication in great apes is crucial to understanding language evolution. Although manual and bodily gestures are considered distinct at a neural level, there has been very limited consideration of potential differences at a behavioural level. In this study, we conducted naturalistic observations of adult wild East African chimpanzees (Pan troglodytes schweinfurthii) in order to establish a repertoire of gestures, and examine intentionality of gesture production, use and comprehension, comparing across manual and bodily gestures. At the population level, 120 distinct gesture types were identified, consisting of 65 manual gestures and 55 bodily gestures. Both bodily and manual gestures were used intentionally and effectively to attain specific goals, by signallers who were sensitive to recipient attention. However, manual gestures differed from bodily gestures in terms of communicative persistence, indicating a qualitatively different form of behavioural flexibility in achieving goals. Both repertoire size and frequency of manual gesturing were more affiliative than bodily gestures, while bodily gestures were more antagonistic. These results indicate that manual gestures may have played a significant role in the emergence of increased flexibility in great ape communication and social bonding.     

Why do gorillas make sequences of gestures?

Great ape gestures have attracted considerable research interest in recent years, prompted by their flexible and intentional pattern of use; but almost all studies have focused on single gestures. Here, we report the first quantitative analysis of sequential gesture use in western gorillas (Gorilla gorilla gorilla), using data from three captive groups and one African study site. We found no evidence that gesture sequences were given for reasons of increased communicative efficiency over single gestures. Longer sequences of repeated gestures did not increase the likelihood of response, and using a sequence was seldom in reaction to communicative failure. Sequential combination of two gestures with similar meanings did not generally increase effectiveness, and sometimes reduced it. Gesture sequences were closely associated with play contexts. Markov transition analysis showed two networks of frequently co-occurring gestures, both consisting of gestures used to regulate play. One network comprised only tactile gestures, the other a mix of silent, audible and tactile gestures; apparently, these clusters resulted from gesture use in play with proximal or distal contact, respectively. No evidence was found for syntactic effects of sequential combination: meanings changed little or not at all. Semantically, many gestures overlapped massively with others in their core information (i.e. message), and gesture messages spanned relatively few functions. We suggest that the underlying semantics of gorilla gestures is highly simplified compared to that of human words. Gesture sequences allow continual adjustment of the tempo and nature of social interactions, rather than generally conveying semantically referential information or syntactic structures.     

交流手势的认知特征

手势是语言交流过程中的一种重要的非语言媒介, 其不仅与语言互动间的关系密切, 而且具有不同的交流认知特征。文章重点归纳和述评了手势和语言交流的关系, 手势相对独立的交流特征, 教育情境中的手势交流。文章具体提出：首先, 手势和语言的共同表达促进了语言的发生和语言的理解、整合和记忆; 其次, 手势一定程度上具有独立的交流性, 手势和语言的“不匹配性”反映了交流信息的变化和交流认知的改变; 最后, 教育情境中教师的手势表达可以引导学生的注意并澄清语言信息, 学生的手势交流有助于促进学习认知过程。未来研究需要进一步探讨手势对于语言交流功能的影响, 语言交流过程中手势交流的优势特征和认知机制, 教育情境中手势交流高效性的认知机制, 手势交流的影响因素、一般特征和个体差异。     

Twelve‐month‐olds’ comprehension and production of pointing

This study explored whether infants aged 12 months already recognize the communicative function of pointing gestures. Infants participated in a task requiring them to comprehend an adult's informative pointing gesture to the location of a hidden toy. They mostly succeeded in this task, which required them to infer that the adult was attempting to direct their attention to a location for a reason – because she wanted them to know that a toy was hidden there. Many of the infants also reversed roles and produced appropriate pointing gestures for the adult in this same game, and indeed there was a correlation such that comprehenders were for the most part producers. These findings indicate that by 12 months of age infants are beginning to show a bidirectional understanding of communicative pointing.     

I See Your Point: Infants Under 12 Months Understand That Pointing Is Communicative

Do young infants understand that pointing gestures allow the pointer to change the information state of a recipient? We used a third-party experimental scenario to examine whether 9- and 11-month-olds understand that a pointer's pointing gesture can inform a recipient about a target object. When the pointer pointed to a target, infants subsequently looked longer when the recipient selected the nontarget rather than the target object. In contrast, infants looked equally long whether the recipient selected the target or nontarget object when the pointer used a noncommunicative gesture, a fist. Finally, when the recipient had no perceptual access to the pointing gesture, infants looked longer when the recipient selected the target rather than the nontarget object. Young infants understand a fundamental aspect of the communicative function of pointing: Pointing, but not all gestures, can transfer information. Gestures may thus be one of the tools infants use for an early understanding of communication.     

The gestural repertoire of the wild chimpanzee

Great ape gestural communication is known to be intentional, elaborate and flexible; yet there is controversy over the best interpretation of the system and how gestures are acquired, perhaps because most studies have been made in restricted, captive settings. Here, we report the first systematic analysis of gesture in a population of wild chimpanzees. Over 266 days of observation, we recorded 4,397 cases of intentional gesture use in the Sonso community, Budongo, Uganda. We describe 66 distinct gesture types: this estimate appears close to asymptote, and the Sonso repertoire includes most gestures described informally at other sites. Differences in repertoire were noted between individuals and age classes, but in both cases, the measured repertoire size was predicted by the time subjects were observed gesturing. No idiosyncratic usages were found, i.e. no gesture type was used only by one individual. No support was found for the idea that gestures are acquired by ‘ontogenetic ritualization’ from originally effective actions; moreover, in detailed analyses of two gestures, action elements composing the gestures did not closely match those of the presumed original actions. Rather, chimpanzee gestures are species-typical; indeed, many are ‘family-typical’, because gesture types recorded in gorillas, orangutans and chimpanzee overlap extensively, with 24 gestures recorded in all three genera. Nevertheless, chimpanzee gestures are used flexibly across a range of contexts and show clear adjustment to audience (e.g. silent gestures for attentive targets, contact gestures for inattentive ones). Such highly intentional use of a species-typical repertoire raises intriguing questions for the evolution of advanced communication.     

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     

Communicative gestures of the hand and arm when 4-year-old sons and their mothers interact

This study investigated a wide range of communicative hand/arm gestures of 4-year-old males when interacting with their mothers. The types of gesture categories observed were in keeping with the predicted encoding ability of this aged child. Pantomimic and deictic gestures were observed in significantly greater numbers than semantic modifying and relational gestures. Although it was found that the mothers' gestural usage reflected the type of gesture categories seen in the children's group, no correlation was found between gesture usage of individual mother-child pairs.     

The development of referential offering in the first year

The ontogeny of referential offers was examined in a longitudinal, within dyad case study of two mother–infant pairs. A combination of microanalytic and qualitative methodologies was employed in describing the functions and morphology of this gesture, as well as its temporal and sequential organization with a number of infant and maternal behaviours. Offers were found to emerge from repetitive, exploratory play routines that provide infants with alternative visual perspectives on objects, and were facilitated by mothers' support of infants' immature attentional, motoric and arousal regulation capacities. Offers were observed to co. occur with maternal behaviours that direct and maintain infants' attention to objects. Our observations suggest that offers are transformed through guided interactions into conventional communicative gestures. Offering arises as mothers become part of the infants' exploratory play routines, gradually changing the function of the behaviour of the infants. These observations are consistent with dynamic systems models of development.     

Rhythmic ostensive gestures: How adults facilitate infants’ entrance into early triadic interactions

For decades, the literature on the emergence of triadic interactions considers the end of the first year of life as the time when children become able to communicate with others intentionally about a referent. Prior to that, children only relate in dyads, either with someone else or with an object. However, several researchers claim that referents are not naturally given in human communication and that they need to be established in interaction with others.In this study, we focus on earlier triadic interactions initiated by adults, when young babies still require an adult to bring the material world within their reach. In these early triadic interactions, ostensive gestures (with the object in the hand) are one of the first means of enabling the establishment of shared reference. Such gestures are easier to understand since sign (gesture) and referent (object) coincide. We conducted a longitudinal study with 6 babies filmed at 2, 3 and 4 months old in interaction with their mothers and a sounding object (a maraca). We analyzed different communicative initiatives by the adult and the child’s responses.The results show that children come to understand the adult’s communicative intention gradually through interaction. Adults include children in organized communicative “niches” based on ostensive actions, both through ostensive gestures and demonstrations of the use of the object. Consequently, the first shared understandings between adult and child take place around the object and its uses. Rhythm is a powerful tool used to structure the interaction. Eventually, adults provide space to children to actively interact with the sounding object themselves. These results highlight the importance of considering ostensive actions as a communicative tool that favors joint attention and action. They also bring some light to the interdependence between a child who actively perceives and acts, and the structured situation that the adult organizes for them.     

Where have all the (ape) gestures gone?

Comparative analysis of the gestural communication of our nearest animal relatives, the great apes, implies that humans should have the biological potential to produce and understand 60–70 gestures, by virtue of shared common descent. These gestures are used intentionally in apes to convey separate requests, rather than as referential items in syntactically structured signals. At present, no such legacy of shared gesture has been described in humans. We suggest that the fate of “ape gestures” in modern human communication is relevant to the debate regarding the evolution of language through a possible intermediate stage of gestural protolanguage.     

Individual differences in the linguistic competence of referential and expressive subjects

The aim of this work was to examine individual differences in referential and expressive style through a longitudinal study. The composition of the first 50 words, communicative gestures, the conversational style of dyads and the percentage of vocabulary produced from 12 to 24 month-olds were analyzed. The vocabulary was collected through interviews to parents and sessions of mother-infant interaction in the laboratory. Significant differences in the proportion of common nouns and frozen phrases between referential and expressive children in the frequency of communicative gestures and style conversation were found. Thus, referential children and their mothers used more pointing gestures than the expressive children and their mothers. Additionally, mothers of referential children used completing more frequently.     

Young children use their hands to tell their mothers what to say

Children produce their first gestures before their first words, and their first gesture+word sentences before their first word+word sentences. These gestural accomplishments have been found not only to predate linguistic milestones, but also to predict them. Findings of this sort suggest that gesture itself might be playing a role in the language‐learning process. But what role does it play? Children's gestures could elicit from their mothers the kinds of words and sentences that the children need to hear in order to take their next linguistic step. We examined maternal responses to the gestures and speech that 10 children produced during the one‐word period. We found that all 10 mothers ‘translated’ their children's gestures into words, providing timely models for how one‐ and two‐word ideas can be expressed in English. Gesture thus offers a mechanism by which children can point out their thoughts to mothers, who then calibrate their speech to those thoughts, and potentially facilitate language‐learning.     

When do gestures communicate? A meta-analysis

Do the gestures that speakers produce while talking significantly benefit listeners' comprehension of the message? This question has been the topic of many research studies over the previous 35 years, and there has been little consensus. The present meta-analysis examined the effect sizes from 63 samples in which listeners' understanding of a message was compared when speech was presented alone with when speech was presented with gestures. It was found that across samples, gestures do provide a significant, moderate benefit to communication. Furthermore, the magnitude of this effect is moderated by 3 factors. First, effects of gesture differ as a function of gesture topic, such that gestures that depict motor actions are more communicative than those that depict abstract topics. Second, effects of gesture on communication are larger when the gestures are not completely redundant with the accompanying speech; effects are smaller when there is more overlap between the information conveyed in the 2 modalities. Third, the size of the effect of gesture is dependent on the age of the listeners, such that children benefit more from gestures than do adults. Remaining questions for future research are highlighted.     

Socially guided attention influences infants’ communicative behavior

For effective prelinguistic communication, infants must be able to direct their attention, vocalizations, and nonverbal gestures in social interactions. The purpose of our study was to examine how different styles of caregiver responses influenced infant attentional and communicative behavior in social interactions, based on prior studies that have shown influences of responsiveness on attention, language and cognitive outcomes. Infants were exposed to redirective and sensitive behavior systematically using an ABA design to examine real-time changes in infants’ behavior as a function of caregiver responses. During the two baseline “A” periods, caregivers were instructed to play as they would at home. During the social response “B” period, caregivers were instructed to respond sensitively to infants’ behavior on one visit and redirectively on the other visit. Results demonstrated that when caregivers behaved redirectively, infants shifted their attention more frequently and decreased the duration of their visual attention. Caregiver responses also resulted in changes in vocal and gesture production. Infants decreased their production of caregiver-directed vocalizations, gestures, and gesture-vocal combinations during in the redirective condition. Results suggest that caregiver sensitive responding to infants’ attentional focus may be one influence on infants’ attentional and prelinguistic communicative behavior.