Attention-sensitive signalling by 7- to 20-month-old infants in a comparative perspective.

Attention-sensitive signalling is the pragmatic skill of signallers who adjust the modality of their communicative signals to their recipient's attention state. This study provides the first comprehensive evidence for its onset and development in 7-to 20-month-olds human infants, and underlines its significance for language acquisition and evolutionary history. Mother-infant dyads (N = 30) were studied in naturalistic settings, sampled according to three developmental periods (in months); [7-10], [11-14], and [15-20]. Infant's signals were classified by dominant perceptible sensory modality and proportions compared according to their mother's visual attention, infant-directed speech and tactile contact. Maternal visual attention and infant-directed speech were influential on the onset and steepness of infants' communicative adjustments. The ability to inhibit silent-visual signals towards visually inattentive mothers (unimodal adjustment) predated the ability to deploy audible-or-contact signals in this case (cross-modal adjustment). Maternal scaffolding of infant's early pragmatic skills through her infant-directed speech operates on the facilitation of infant's unimodal adjustment, the preference for oral over gestural signals, and the audio-visual combinations of signals. Additionally, breakdowns in maternal visual attention are associated with increased use of the audible-oral modality/channel. The evolutionary role of the sharing of attentional resources between parents and infants into the emergence of modern language is discussed.

Patterns of attention-sensitive communication contribute to 7-20-month-olds' emerging pragmatic skills.

The present study aimed at investigating the ability of 7- to 20-month-old infants to display attention-sensitive communication using either canonical markers of language acquisition (e.g., pointing gestures, canonical babblings) or other signals based on the physical features actually perceived by the mother in everyday interaction (e.g., body movements, mouth sounds). We studied 30 French mother-infant dyads in naturalistic settings. We assessed the infants' attention-sensitive communication through unimodal and cross-modal adjustment, defined as the capacity of infants to address visually inattentive mothers by avoiding visual communication mismatches and/or favoring communication matches through audible-or-contact signals. Unimodal and cross-modal adjustments were tested for specific signals across spontaneous "conditions" of maternal visual attention (attentive/inattentive) from video footage filmed in the home. Both canonical markers of language development and signals belonging to an extended repertoire of communication were used by infants to adjust to their mother's visual attention. Gaze-coordinated signals were overall not significantly better adjusted to maternal attention than non-gaze-coordinated signals, except for specific silent-visual signals at certain ages. Overall, these results indicate that attention-sensitive communication is relevant to the development of early pragmatic skills and that the intentional use of signals may be more reliably approximated by this capacity than by gaze-coordination with signals.

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

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.

Sensitivity to the communicative partner's attentional state: A developmental study on mother-infant dyads in wild chimpanzees (Pan troglodytes schweinfurthii).

Gestural communication permeates all domains of chimpanzees' social life and is intentional in use. However, we still have only limited information on how young apes develop the sociocognitive skills needed for intentional communication. In this cross-sectional study, we document the development of behavioral adjustment to the recipient's visual attention-considered a hallmark of intentional communication-in wild immature chimpanzees' gestural communication. We studied 11 immature chimpanzees (Pan troglodytes schweinfurthii): three infants, four juveniles, and four adolescents gesturing towards their mother. We quantified silent-visual, audible, and contact gestures indexed to maternal visual attention and inattention. We investigated unimodal adjustment, defined by the capacity of young chimpanzees to deploy fewer silent-visual signals when their mothers did not show full visual attention towards them as compared with when they did. We then examined cross-modal adjustment, defined as the capacity of chimpanzees to deploy more audible-or-contact gestures than silent-visual gestures in the condition where their mothers did not show full visual attention as compared to when they did. Our results show a gradual decline in the use of silent-visual gestures when the mother is not visually attentive with increasing age. The absence of silent-visual gesture production toward a visually inattentive recipient (complete unimodal adjustment) was not fully in place until adolescence. Immature chimpanzees used more audible-or-contact gestures than silent-visual ones when their mothers did not show visual attention and vice-versa when they did. This cross-modal adjustment was expressed in juveniles and adolescents but not in infants. Overall, this study shows that infant chimpanzees were limited in their sensitivity to maternal attention when gesturing, whereas adolescent chimpanzees adjusted their communication appropriately. Juveniles present an intermediate pattern with cross-modal adjustment preceding unimodal adjustment and with variability in the age of onset.

Schoolchildren cooperate more successfully with non-kin than with siblings.

Cooperation plays a key role in the development of advanced societies and can be stabilized through shared genes (kinship) or reciprocation. In humans, cooperation among kin occurs more readily than cooperation among non-kin. In many organisms, cooperation can shift with age (e.g. helpers at the nest); however, little is known about developmental shifts between kin and non-kin cooperation in humans. Using a cooperative game, we show that 3- to 10-year-old French schoolchildren cooperated less successfully with siblings than with non-kin children, whether or not non-kin partners were friends. Furthermore, children with larger social networks cooperated better and the perception of friendship among non-friends improved after cooperating. These results contrast with the well-established preference for kin cooperation among adults and indicate that non-kin cooperation in humans might serve to forge and extend non-kin social relationships during middle childhood and create opportunities for future collaboration beyond kin. Our results suggest that the current view of cooperation in humans may only apply to adults and that future studies should focus on how and why cooperation with different classes of partners might change during development in humans across cultures as well as other long-lived organisms.

Is Conceptual Diversity an Advantage for Scientific Inquiry? A Case Study on the Concept of 'Gesture' in Comparative Psychology.

Growing scientific fields often involve multidisciplinary investigations in which the same concepts may have different meanings. Here, we examine the case of 'gesture' in comparative research to depict how conceptual diversity hidden by the label 'gesture' can lead to consistently divergent interpretations in humans and nonhuman primates. We show that definitions of 'gesture' drastically differ regarding the forms of a gesture and the cognitive processes inferred from it, and that these differences emerge from implicit assumptions which have pervasive consequences on the interpretations claimed by researchers. We then demonstrate that implicit assumptions about scientific concepts can be made explicit using a finite set of operational criteria. We argue that developing theoretical definitions systematically associated with operational conceptual boundaries would allow to tackle both the challenges of maintaining high internal coherence within studies and of improving comparability and replicability of scientific results. We thus offer an easy-to-implement conceptual tool that should help ground valid comparisons between studies and serve scientific inquiry.

Gestural communication in olive baboons (Papio anubis): repertoire and intentionality.

Gesturing is a widespread phenomenon in the animal kingdom, as well as an important facet of human language. As such, studying the communicative gestures of our close phylogenetic relatives is essential to better understand its evolution. While recent studies have shown that ape gestural communication shares some properties with human language, very little is known about the properties of gestural communication in monkeys. The aims of this study were to establish the first quantitative repertoire of gestural communication in a species of old-world monkeys, the olive baboon Papio anubis, and to determine its properties in terms of variability, flexibility, and intentionality. Gestural communication was continuously recorded on 47 captive olive baboons over 1 year. Their gestural repertoire was composed of 67 visual, tactile, and audible gestures, which were used flexibly across different contexts, indicating means-ends dissociation. We found that the use of gestures was variable across individuals and ages, notably with repertoire size decreasing with age. Baboons used their gestures intentionally; gesturers looked at the recipient, waited for a response, and took into account the attentional state of their recipient. Particularly, they actively adjusted the modality of their gesture to the recipient's visual attention, using more visual gestures when the recipient was attending and more tactile gestures when the recipient was not. Thus, the gestural communicative system of olive baboons possesses properties which are similar to the ones of apes and to human language. These intentional features of gestural communication, that may constitute a prerequisite of language evolution, may have been present in the common ancestor of baboons and humans, around 30-40 million years ago.

Acquisition of joint attention by olive baboons gesturing toward humans.

Joint attention is a core ability of human social cognition which broadly refers to the coordination of attention with both the presence and activity of social partners. In both human and non-human primates, joint attention can be assessed from behaviour; gestures and gaze alternation between the partner and a distal object are standard behavioural manifestations of joint attention. Here we examined the acquisition of joint attention in olive baboons as a function of their individual experience of a human partner's attentional states during training regimes. Eleven olive baboons (Papio anubis) were observed during their training to perform food-requesting gestures, which occurred either by (1) a human facing them (face condition), or (2) by a human positioned in profile who never turned to them (profile condition). We found neither gestures nor gaze alternation were present at the start of the training but rather developed over the training period. Only baboons in the face condition showed an increase in the number of gaze alternations, and their gaze pattern progressively shifted to a coordinated sequence in which gazes and gestures were coordinated in time. In contrast, baboons trained by a human in profile showed significantly less coordination of gazes with gestures but still learned to request food with their gestures. These results suggest that the partner's social attention plays an important role in the acquisition of visual joint attention and, to a lesser extent, in gesture learning in baboons. Interspecific interactions appear to offer rich opportunities to manipulate and thus identify the social contexts in which socio-communicative skills develop.

Baboon (Papio anubis) chimeric face processing by human (Homo sapiens) judges: Influence of stimuli complexity on the perception of oro-facial asymmetries.

Two methodologies have traditionally been used to measure hemispheric specialization for perception and expression of emotions in human and nonhuman primates. The first refers to objective measures, that is, measures of area and length of facial features, and the second concerns subjective "measures," that is, assessment of chimeric faces by human judges. We proposed a refined approach to the subjective assessment of hemispheric specializations, which aims at delimiting methodological issues in the study of orofacial asymmetries. The study focused on a baboon threat orofacial expression, which has led to discordant results according to the methodology used (Wallez & Vauclair, 2011, 2013). We presented human participants with two sets of chimeric stimuli varying the regions of the face likely to be processed. The whole face set was composed of classical chimeric faces, and the upper face set was made of chimeric faces for which the lower part was blurred. The purpose of this new procedure was to shed light on the perception process of baboon faces by human participants during a free-viewing chimeric task. Results showed a concomitant influence of the chimera structure depending on the order of the presentation of the set, revealing a training effect in our human judges. These factors combined together allowed the appearance of an overall left-left chimeric choice by human judges (i.e., which indicates a right hemisphere involvement in baboon threat expression). These findings bring novel insights into the study of orofacial asymmetries in nonhuman primates by human judgments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Manipulating social cues in baboon gesture learning: what does it tell us about the evolution of communication?

Reading the attentional state of an audience is crucial for effective intentional communication. This study investigates how individual learning experience affects subsequent ability to tailor gestural communication to audience visual attention. Olive baboons were atypically trained to request food with gestures by a human standing in profile, while not having access to her face. They were tested immediately after training, and then 1 year later in conditions that varied the human's cues to attention. In immediate testing, these baboons (profile group baboons) gestured towards untrained cues regardless of their relevance for visual communication. They were also less discriminant towards trained versus untrained cues than baboons trained by a human facing them (face group baboons, tested in Bourjade et al. Anim Behav 87:121-128; Bourjade et al., Anim Behav 87:121-128, 2014). In delayed testing, the number of gestures towards meaningful untrained cues increased and profile group baboons discriminated the orientation of the human body, a conspicuous proxy of visual attention. Our results provide support for the primary interplay between implicit learning and systematically reinforced associations made through explicit training in the scaffolding of intentional gesturing tuned to audience attention.

Investigating determinants of yawning in the domestic (Equus caballus) and Przewalski (Equus ferus przewalskii) horses.

Yawning is rare in herbivores which therefore may be an interesting group to disentangle the potential function(s) of yawning behaviour. Horses provide the opportunity to compare not only animals living in different conditions but also wild versus domestic species. Here, we tested three hypotheses by observing both domestic and Przewalski horses living in semi-natural conditions: (i) that domestic horses may show an elevated rate of yawning as a result of the domestication process (or as a result of life conditions), (ii) that individuals experiencing a higher level of social stress would yawn more than individuals with lower social stress and (iii) that males would yawn more often than females. The study involved 19 Przewalski horses (PHs) and 16 domestic horses (DHs) of different breeds living in large outdoor enclosures. The results showed that there was no difference between the PH and DH in yawning frequency (YF). PHs exhibited much higher levels of social interactions than DHs. There was a positive correlation between yawning frequency and aggressive behaviours in PHs, especially males, supporting the idea that yawning may be associated with more excitatory/stressful social situations. A correlation was found between yawning frequency and affiliative behaviours in DHs, which supports the potential relationship between yawning and social context. Finally, the entire males, but not castrated males, showed much higher levels of yawning than females in both species. The intensity (rather than the valence) of the interaction may be important in triggering yawning, which could therefore be a displacement activity that helps reduce tension.

Social interaction is associated with changes in infants' motor activity.

BACKGROUND: In developmental research, infants are commonly assumed to be early stakeholders in interactions with their caregivers. The tools that infants can use to interact with others vary from visual contact to smiling or vocalizing, and also include motor activity. However, surprisingly few studies have explored how the nature and context of social interactions affect infants' engagement in motor activity. METHODS: We investigated the kinematic properties of foot and face movements produced by 11 infants aged between 5 and 9 months during six contrasting dyadic episodes (i.e. passive presence of a stranger or the infant's mother, weak or intense interaction with the stranger/mother as she sings a nursery play song). RESULTS: The infants' face and foot motor activity was significantly reduced during the interactive episodes, compared with the episodes without any interaction, in both the mother and stranger conditions. Furthermore, the level of their motor activity was significantly lower in the stranger condition than in the mother one for some parameters. CONCLUSION: These results are in line with those reported by previous studies and confirm the relevance of using motor activity to delineate the early forms of interactive episodes in infants.

Is leadership a reliable concept in animals? An empirical study in the horse.

Leadership is commonly invoked when accounting for the coordination of group movements in animals, yet it remains loosely defined. In parallel, there is increased evidence of the sharing of group decisions by animals on the move. How leadership integrates within this recent framework on collective decision-making is unclear. Here, we question the occurrence of leadership in horses, a species in which this concept is of prevalent use. The relevance of the three main definitions of leadership--departing first, walking in front travel position, and eliciting the joining of mates--was tested on the collective movements of two semi-free ranging groups of Przewalski horses (Equus ferus przewalskii). We did not find any leader capable of driving most group movements or recruiting mates more quickly than others. Several group members often displayed pre-departure behaviours at the same time, and the simultaneous departure of several individuals was common. We conclude that the decision-making process was shared by several group members a group movement (i.e., partially shared consensus) and that the leadership concept did not help to depict individual departure and leading behaviour across movements in both study groups. Rather, the different proxies of leadership produced conflicting information about individual contributions to group coordination. This study discusses the implications of these findings for the field of coordination and decision-making research.

Training experience in gestures affects the display of social gaze in baboons' communication with a human.

Gaze behaviour, notably the alternation of gaze between distal objects and social partners that accompanies primates' gestural communication is considered a standard indicator of intentionality. However, the developmental precursors of gaze behaviour in primates' communication are not well understood. Here, we capitalized on the training in gestures dispensed to olive baboons (Papio anubis) as a way of manipulating individual communicative experience with humans. We aimed to delineate the effects of such a training experience on gaze behaviour displayed by the monkeys in relation with gestural requests. Using a food-requesting paradigm, we compared subjects trained in requesting gestures (i.e. trained subjects) to naïve subjects (i.e. control subjects) for their occurrences of (1) gaze behaviour, (2) requesting gestures and (3) temporal combination of gaze alternation with gestures. We found that training did not affect the frequencies of looking at the human's face, looking at food or alternating gaze. Hence, social gaze behaviour occurs independently from the amount of communicative experience with humans. However, trained baboons-gesturing more than control subjects-exhibited most gaze alternation combined with gestures, whereas control baboons did not. By reinforcing the display of gaze alternation along with gestures, we suggest that training may have served to enhance the communicative function of hand gestures. Finally, this study brings the first quantitative report of monkeys producing requesting gestures without explicit training by humans (controls). These results may open a window on the developmental mechanisms (i.e. incidental learning vs. training) underpinning gestural intentional communication in primates.

Bonobos and orangutans, but not chimpanzees, flexibly plan for the future in a token-exchange task.

Non-human animals, including great apes, have been suggested to share some of the skills for planning that humans commonly exhibit. A crucial difference between human and non-human planning may relate to the diversity of domains and needs in which this skill is expressed. Although great apes can save tools for future use, there is little evidence yet that they can also do so in other contexts. To investigate this question further, we presented the apes with a planning token-exchange task that differed from standard tool-use tasks. Additionally, we manipulated the future outcome of the task to investigate planning flexibility. In the Exchange condition, subjects had to collect, save and transport tokens because they would need them 30 min later to exchange them for food with a human, i.e., "bring-back" response. In the Release condition, the collection and transport of tokens were not needed as no exchange took place after 30 min. Out of 13 subjects, eight solved the task at least once in the Exchange condition, with chimpanzees appearing less successful than the other species. Importantly, three individuals showed a clear differential response between conditions by producing more "bring-back" responses in the Exchange than in the Release conditions. Those bonobo and orangutan individuals hence adapted their planning behavior according to changing needs (i.e., they brought tokens back significantly more often when they would need them). Bonobos and orangutans, unlike chimpanzees, planned outside the context of tool-use, thus challenging the idea that planning in these species is purely domain-specific.

Baboons' hand preference resists to spatial factors for a communicative gesture but not for a simple manipulative action.

Olive baboons (Papio anubis) do acquire and use intentional requesting gestures in experimental contexts. Individual's hand preference for these gestures is consistent with that observed for typical communicative gestures, but not for manipulative actions. Here, we examine whether the strength of hand preference may also be a good marker of hemispheric specialization for communicative gestures, hence differing from the strength of hand preference for manipulative actions. We compared the consistency of individuals' hand preference with regard to the variation in space of either (i) a communicative partner or (ii) a food item to grasp using a controlled set-up. We report more consistent hand preference for communicative gestures than for grasping actions. Established hand preference in the midline was stronger for gesturing than for grasping and allowed to predict the consistency of hand preference across positions. We found no significant relation between the direction of hand preference and the task.

To beg, or not to beg? That is the question: mangabeys modify their production of requesting gestures in response to human's attentional states.

BACKGROUND: Although gestural communication is widespread in primates, few studies focused on the cognitive processes underlying gestures produced by monkeys. METHODOLOGY/PRINCIPAL FINDINGS: The present study asked whether red-capped mangabeys (Cercocebus torquatus) trained to produce visually based requesting gestures modify their gestural behavior in response to human's attentional states. The experimenter held a food item and displayed five different attentional states that differed on the basis of body, head and gaze orientation; mangabeys had to request food by extending an arm toward the food item (begging gesture). Mangabeys were sensitive, at least to some extent, to the human's attentional state. They reacted to some postural cues of a human recipient: they gestured more and faster when both the body and the head of the experimenter were oriented toward them than when they were oriented away. However, they did not seem to use gaze cues to recognize an attentive human: monkeys begged at similar levels regardless of the experimenter's eyes state. CONCLUSIONS/SIGNIFICANCE: These results indicate that mangabeys lowered their production of begging gestures when these could not be perceived by the human who had to respond to it. This finding provides important evidence that acquired begging gestures of monkeys might be used intentionally.

Are monkeys able to plan for future exchange?

Whether or not non-human animals can plan for the future is a hotly debated issue. We investigate this question further and use a planning-to-exchange task to study future planning in the cooperative domain in two species of monkeys: the brown capuchin (Cebus apella) and the Tonkean macaque (Macaca tonkeana). The rationale required subjects to plan for a future opportunity to exchange tokens for food by collecting tokens several minutes in advance. Subjects who successfully planned for the exchange task were expected to select suitable tokens during a collection period (5/10 min), save them for a fixed period of time (20/30 min), then take them into an adjacent compartment and exchange them for food with an experimenter. Monkeys mostly failed to transport tokens when entering the testing compartment; hence, they do not seem able to plan for a future exchange with a human partner. Three subjects did however manage to solve the task several times, albeit at very low rates. They brought the correct version of three possible token types, but rarely transported more than one suitable token at a time. Given that the frequency of token manipulation predicted transport, success might have occurred by chance. This was not the case, however, since in most cases subjects were not already holding the token in their hands before they entered the testing compartment. Instead, these results may reflect subjects' strengths and weaknesses in their time-related comprehension of the task.

On the significance of adult play: what does social play tell us about adult horse welfare?

Play remains a mystery and adult play even more so. More typical of young stages in healthy individuals, it occurs rarely at adult stages but then more often in captive/domestic animals, which can imply spatial, social and/or feeding deprivations or restrictions that are challenging to welfare, than in animals living in natural conditions. Here, we tested the hypothesis that adult play may reflect altered welfare states and chronic stress in horses, in which, as in several species, play rarely occurs at adult stages in natural conditions. We observed the behaviour (in particular, social play) of riding school horses during occasional outings in a paddock and measured several stress indicators when these horses were in their individual home boxes. Our results revealed that (1) the number of horses and rates of adult play appeared very high compared to field report data and (2) most stress indicators measured differed between 'players' and 'non-players', revealing that most 'playful' animals were suffering from more chronic stress than 'non-playful' horses. Frequency of play behaviour correlated with a score of chronic stress. This first discovery of a relationship between adult play and altered welfare opens new lines of research that certainly deserves comparative studies in a variety of species.