Embodying Similarity and Difference: The Effect of Listing and Contrasting Gestures During U.S. Political Speech

Public speakers like politicians carefully craft their words to maximize the clarity, impact, and persuasiveness of their messages. However, these messages can be shaped by more than words. Gestures play an important role in how spoken arguments are perceived, conceptualized, and remembered by audiences. Studies of political speech have explored the ways spoken arguments are used to persuade audiences and cue applause. Studies of politicians' gestures have explored the ways politicians illustrate different concepts with their hands, but have not focused on gesture's potential as a tool of persuasion. Our paper combines these traditions to ask first, how politicians gesture when using spoken rhetorical devices aimed at persuading audiences, and second, whether these gestures influence the ways their arguments are perceived. Study 1 examined two rhetorical devices-contrasts and lists-used by three politicians during U.S. presidential debates and asked whether the gestures produced during contrasts and lists differ. Gestures produced during contrasts were more likely to involve changes in hand location, and gestures produced during lists were more likely to involve changes in trajectory. Study 2 used footage from the same debates in an experiment to ask whether gesture influenced the way people perceived the politicians' arguments. When participants had access to gestural information, they perceived contrasted items as more different from one another and listed items as more similar to one another than they did when they only had access to speech. This was true even when participants had access to only gesture (in muted videos). We conclude that gesture is effective at communicating concepts of similarity and difference and that politicians (and likely other speakers) take advantage of gesture's persuasive potential.

Overcoming bias in the comparison of human language and animal communication

Human language is a powerful communicative and cognitive tool. Scholars have long sought to characterize its uniqueness, but each time a property is proposed to set human language apart (e.g., reference, syntax), some (attenuated) version of that property is found in animals. Recently, the uniqueness argument has shifted from linguistic rules to cognitive capacities underlying them. Scholars argue that human language is unique because it relies on ostension and inference, while animal communication depends on simple associations and largely hardwired signals. Such characterizations are often borne out in published data, but these empirical findings are driven by radical differences in the ways animal and human communication are studied. The field of animal communication has been dramatically shaped by the "code model," which imagines communication as involving information packets that are encoded, transmitted, decoded, and interpreted. This framework standardized methods for studying meaning in animal signals, but it does not allow for the nuance, ambiguity, or contextual variation seen in humans. The code model is insidious. It is rarely referenced directly, but it significantly shapes how we study animals. To compare animal communication and human language, we must acknowledge biases resulting from the different theoretical models used. By incorporating new approaches that break away from searching for codes, we may find that animal communication and human language are characterized by differences of degree rather than kind.

Joyful by nature: approaches to investigate the evolution and function of joy in non-human animals

The nature and evolution of positive emotion is a major question remaining unanswered in science and philosophy. The study of feelings and emotions in humans and animals is dominated by discussion of affective states that have negative valence. Given the clinical and social significance of negative affect, such as depression, it is unsurprising that these emotions have received more attention from scientists. Compared to negative emotions, such as fear that leads to fleeing or avoidance, positive emotions are less likely to result in specific, identifiable, behaviours being expressed by an animal. This makes it particularly challenging to quantify and study positive affect. However, bursts of intense positive emotion (joy) are more likely to be accompanied by externally visible markers, like vocalisations or movement patterns, which make it more amenable to scientific study and more resilient to concerns about anthropomorphism. We define joy as intense, brief, and event-driven (i.e. a response to something), which permits investigation into how animals react to a variety of situations that would provoke joy in humans. This means that behavioural correlates of joy are measurable, either through newly discovered 'laughter' vocalisations, increases in play behaviour, or reactions to cognitive bias tests that can be used across species. There are a range of potential situations that cause joy in humans that have not been studied in other animals, such as whether animals feel joy on sunny days, when they accomplish a difficult feat, or when they are reunited with a familiar companion after a prolonged absence. Observations of species-specific calls and play behaviour can be combined with biometric markers and reactions to ambiguous stimuli in order to enable comparisons of affect between phylogenetically distant taxonomic groups. Identifying positive affect is also important for animal welfare because knowledge of positive emotional states would allow us to monitor animal well-being better. Additionally, measuring if phylogenetically and ecologically distant animals play more, laugh more, or act more optimistically after certain kinds of experiences will also provide insight into the mechanisms underlying the evolution of joy and other positive emotions, and potentially even into the evolution of consciousness.

Gesture

Gesture is intimately entwined with human language and thought. It is a tool for communication as well as cognition: conveying information to interlocutors, orchestrating interaction, and supporting problem-solving and learning. Over the past 25 years, the community of scholars interested in gesture has grown from a specialized group to a multidisciplinary community incorporating gesture into a wide range of topics. This article aims to capture and continue that growth by introducing readers to some of the most intriguing findings and questions in gesture research. It adopts a four-field approach, integrating multiple literatures and introducing work from outside anthropology. It defines key terminology and reviews five areas that have undergone significant recent growth: the integration of gesture with speech, gesture as communication and cognition, gesture's role in learning and language development, cultural variation in gesture, and the role of gesture in language origins. Taken together, these areas demonstrate that gesture is entangled with language, thought, and identity, starting in early childhood. This tangle has deep evolutionary roots; indeed, gesture may have been part of the human story from its start.

Expected final online publication date for the Annual Review of Anthropology Volume 51 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A robust tool kit: First report of tool use in captive crested capuchin monkeys (Sapajus robustus)

Primate tool use is of great interest but has been reported only in a limited number of species. Here we report tool use in crested capuchin monkeys (Sapajus robustus), an almost completely unstudied robust capuchin species. Crested capuchins and their sister species, the yellow-breasted capuchin, diverged from a common ancestor over 2 million years ago, so this study fills a significant gap in understanding of tool use capacity and variation within the robust capuchin monkey radiation. Our study group was a captive population of seven individuals at the Santa Ana Zoo in California. The monkeys were given no prior training, and they were provided with a variety of enrichment items, including materials that could be used as tools as well as hard-to-access resources, for open-ended interactions. In 54 observation hours, monkeys performed eleven tool use actions: digging, hammering, probing, raking, sponging, striking, sweeping, throwing, waving, wedging, and wiping. We observed tool modification, serial tool use, and social learning opportunities, including monkeys' direct observation of tool use and tolerated scrounging of foods obtained through tool use. We also observed significant individual skew in tool use frequency, with one individual using tools daily, and two individuals never using tools during the study. While crested capuchins have never been reported to use tools in the wild, our findings provide evidence for the species' capacity and propensity for tool use, highlighting the urgent need for research on this understudied, endangered primate. By providing detailed data on clearly identified S. robustus individuals, this study marks an effort to counteract the overgeneralization in the captive literature in referring to any robust capuchins of unknown provenance or ancestry as Cebus apella, a practice that obfuscates potential differences among species in tool use performance and repertoire in one of the only species-rich tool-using genera in the world.

Just kidding: the evolutionary roots of playful teasing

Accounts of teasing have a long history in psychological and sociological research, yet teasing itself is vastly underdeveloped as a topic of study. As a phenomenon that moves along the border between aggression and play, teasing presents an opportunity to investigate key foundations of social and mental life. Developmental studies suggest that preverbal human infants already playfully tease their parents by performing 'the unexpected,' apparently deliberately violating the recipient's expectations to create a shared humorous experience. Teasing behaviour may be phylogenetically old and perhaps an evolutionary precursor to joking. In this review, we present preliminary evidence suggesting that non-human primates also exhibit playful teasing. In particular, we argue that great apes display three types of playful teasing described in preverbal human infants: teasing with offer and withdrawal, provocative non-compliance and disrupting others' activities. We highlight the potential of this behaviour to provide a window into complex socio-cognitive processes such as attribution of others' expectations and, finally, we propose directions for future research and call for systematic studies of teasing behaviour in non-human primates.

Developmental perspectives on primate gesture: 100 years in the making

This paper is an introduction to the special issue entitled Evolving the study of gesture: evaluating and unifying theories of gesture acquisition in great apes. The gestures of great apes have been recorded in scientific literature for over 100 years, but the ways in which apes acquire their gestures remains a highly debated topic. Through this historical framework, we summarize and contextualize contemporary research on the development of ape gesture. We describe the papers presented in this special issue, grouping them into three themes: assessing theories, methodological innovation, and new empirical approaches. Each of the papers is a significant contribution to the literature on ape gesture, but the collection of work together represents a unique collaboration across labs, theories, and studied species. By considering the papers side-by-side, we hope that readers will see the authors as engaging in a true dialogue, one which will help the field of primate gesture research make significant advances in the years to come.

Gesturing towards the future: cognition, big data, and the future of comparative gesture research

The field of ape gesture research has grown significantly in the past two decades, but progress on the question of gesture development has been limited by methodological and terminological disagreements, small sample sizes, and a lack of fine-grained longitudinal data. The main theories of gesture acquisition are often portrayed as mutually exclusive, but only some theories actually detail learning mechanisms, and differences in the level of analysis may help explain some of the apparent disagreements. Gesture research would benefit greatly from the articulation of more testable hypotheses. We propose two hypotheses that follow from dominant theories of gesture acquisition. We urge scholars to collect new data and leverage existing data in ways that maximize the potential for comparison across datasets and articulation with studies of other communicative modalities. Finally, we advocate for a transition away from using intentionality as a marker of the 'special status' of gesture, and towards using gesture as a window onto the lives and minds of apes.

The development of iconicity in children's co-speech gesture and homesign

Gesture can illustrate objects and events in the world by iconically reproducing elements of those objects and events. Children do not begin to express ideas iconically, however, until after they have begun to use conventional forms. In this paper, we investigate how children's use of iconic resources in gesture relates to the developing structure of their communicative systems. Using longitudinal video corpora, we compare the emergence of manual iconicity in hearing children who are learning a spoken language (co-speech gesture) to the emergence of manual iconicity in a deaf child who is creating a manual system of communication (homesign). We focus on one particular element of iconic gesture - the shape of the hand (handshape). We ask how handshape is used as an iconic resource in 1-5-year-olds, and how it relates to the semantic content of children's communicative acts. We find that patterns of handshape development are broadly similar between co-speech gesture and homesign, suggesting that the building blocks underlying children's ability to iconically map manual forms to meaning are shared across different communicative systems: those where gesture is produced alongside speech, and those where gesture is the primary mode of communication.

Mind the Gap

Children from poor families typically know fewer words when they enter school than children from wealthy families do. This “word gap” persists over time and may significantly affect educational achievement. The language children hear at home before they start school influences how many words they learn. Children from poorer families typically hear fewer words. New programs tackle the language gap by encouraging poorer parents to talk more to their children. These programs have excellent intentions, but they also have significant limitations. They count only the number of words, ignoring important differences in how language is used in social and physical contexts. They also carry implicit ideologies about “correct” language practices and may stigmatize some parents or cultures. To succeed in leveling the playing field in early education, interventions should consider features of language beyond the word and partner more closely with parents to create sustainable programs tailored to the desires and practices of local communities.

Perceiving referential intent: Dynamics of reference in natural parent-child interactions

Two studies are presented which examined the temporal dynamics of the social-attentive behaviors that co-occur with referent identification during natural parent-child interactions in the home. Study 1 focused on 6.2 h of videos of 56 parents interacting during everyday activities with their 14-18 month-olds, during which parents uttered common nouns as parts of spontaneously occurring utterances. Trained coders recorded, on a second-by-second basis, parent and child attentional behaviors relevant to reference in the period (40 s) immediately surrounding parental naming. The referential transparency of each interaction was independently assessed by having naïve adult participants guess what word the parent had uttered in these video segments, but with the audio turned off, forcing them to use only non-linguistic evidence available in the ongoing stream of events. We found a great deal of ambiguity in the input along with a few potent moments of word-referent transparency; these transparent moments have a particular temporal signature with respect to parent and child attentive behavior: it was the object's appearance and/or the fact that it captured parent/child attention at the moment the word was uttered, not the presence of the object throughout the video, that predicted observers' accuracy. Study 2 experimentally investigated the precision of the timing relation, and whether it has an effect on observer accuracy, by disrupting the timing between when the word was uttered and the behaviors present in the videos as they were originally recorded. Disrupting timing by only ±1 to 2 s reduced participant confidence and significantly decreased their accuracy in word identification. The results enhance an expanding literature on how dyadic attentional factors can influence early vocabulary growth. By hypothesis, this kind of time-sensitive data-selection process operates as a filter on input, removing many extraneous and ill-supported word-meaning hypotheses from consideration during children's early vocabulary learning.

Pointing and naming are not redundant: children use gesture to modify nouns before they modify nouns in speech

Nouns form the first building blocks of children's language but are not consistently modified by other words until around 2.5 years of age. Before then, children often combine their nouns with gestures that indicate the object labeled by the noun, for example, pointing at a bottle while saying "bottle." These gestures are typically assumed to be redundant with speech. Here we present data challenging this assumption, suggesting that these early pointing gestures serve a determiner-like function (i.e., point at bottle + "bottle" = that bottle). Using longitudinal data from 18 children (8 girls), we analyzed all utterances containing nouns and focused on (a) utterances containing an unmodified noun combined with a pointing gesture and (b) utterances containing a noun modified by a determiner. We found that the age at which children first produced point + noun combinations predicted the onset age for determiner + noun combinations. Moreover, point + noun combinations decreased following the onset of determiner + noun constructions. Importantly, combinations of pointing gestures with other types of speech (e.g., point at bottle + "gimme" = gimme that) did not relate to the onset or offset of determiner + noun constructions. Point + noun combinations thus appear to selectively predict the development of a new construction in speech. When children point to an object and simultaneously label it, they are beginning to develop their understanding of nouns as a modifiable unit of speech.

A word in the hand: action, gesture and mental representation in humans and non-human primates

The movements we make with our hands both reflect our mental processes and help to shape them. Our actions and gestures can affect our mental representations of actions and objects. In this paper, we explore the relationship between action, gesture and thought in both humans and non-human primates and discuss its role in the evolution of language. Human gesture (specifically representational gesture) may provide a unique link between action and mental representation. It is kinaesthetically close to action and is, at the same time, symbolic. Non-human primates use gesture frequently to communicate, and do so flexibly. However, their gestures mainly resemble incomplete actions and lack the representational elements that characterize much of human gesture. Differences in the mirror neuron system provide a potential explanation for non-human primates' lack of representational gestures; the monkey mirror system does not respond to representational gestures, while the human system does. In humans, gesture grounds mental representation in action, but there is no evidence for this link in other primates. We argue that gesture played an important role in the transition to symbolic thought and language in human evolution, following a cognitive leap that allowed gesture to incorporate representational elements.

Orangutans modify their gestural signaling according to their audience's comprehension

When people are not fully understood, they persist with attempts to communicate, elaborating their speech in order to better convey their meaning [1]. We investigated whether captive orangutans (Pongo pygmaeus and Pongo abelii) would use analogous communicative strategies in signaling to a human experimenter, and whether they could distinguish different degrees of misunderstanding. Orangutans' behavior varied according to how well they had apparently been understood. When their aims were not met, they persisted in communicative attempts. However, when the interlocutor appeared partially to understand their meaning, orangutans narrowed down their range of signals, focusing on gestures already used and repeating them frequently. In contrast, when completely misunderstood, orangutans elaborated their range of gestures, avoiding repetition of failed signals. It is therefore possible, from communicative signals alone, to determine how well an orangutan's intended goal has been met. This differentiation might function under natural conditions to allow an orangutan's intended goals to be understood more efficiently. In the absence of conventional labels, communicating the fact that an intention has been somewhat misunderstood is an important way to establish shared meaning.