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Early studies attempting interspecies communication with great apes trained to use sign language and Augmented Interspecies Communication (AIC) devices were limited by methodological and technological constraints, as well as restrictive sample sizes. Evidence for animals intentional production of symbols was met with considerable criticisms which could not be easily deflected with existing data. More recently, thousands of pet dogs have been trained with AIC devices comprising soundboards of buttons that can be pressed to produce prerecorded human words or phrases. However, the nature of pets button presses remains an open question: are presses deliberate, and potentially meaningful? Using a large dataset of button presses by family dogs and their owners, we investigate whether dogs button presses are (i) non-accidental, (ii) non-random, and (iii) not mere repetitions of their owners presses. Our analyses reveal that, at the population level, soundboard use by dogs cannot be explained by random pressing, and that certain two-button concept combinations appear more often than expected by chance at the population level. We also find that dogs presses are not perfectly predicted by their owners, suggesting that dogs presses are not merely repetitions of human presses, therefore suggesting that dog soundboard use is deliberate.

Past research on interspecies communication has shown that animals can be trained to use Augmentative Interspecies Communication (AIC) devices, such as soundboards, to make simple requests of their caretakers. The recent uptake in AIC devices by hundreds of pet owners around the world offers a novel opportunity to investigate whether AIC is possible with owner-trained family dogs. To answer this question, we carried out two studies to test pet dogs ability to recognise and respond appropriately to food-related, play-related, and outside-related words on their soundboards. One study was conducted by researchers, and the other by citizen scientists who followed the same procedure. Further, we investigated whether these behaviours depended on the identity of the person presenting the word (unfamiliar person or dogs owner) and the mode of its presentation (spoken or produced by a pressed button). We find that dogs produced contextually appropriate behaviours for both play-related and outside-related words regardless of the identity of the person producing them and the mode in which they were produced. Therefore, pet dogs can be successfully taught by their owners to associate words recorded onto soundboard buttons to their outcomes in the real world, and they respond appropriately to these words even when they are presented in the absence of any other cues, such as the owners body language.

Recognizing and appropriately responding to others' helpful actions are critical components of social cognition and reciprocity. This ability has been well-documented in various species where animals differentiate between experimenters who are “unwilling” versus “unable” to provide help, but it is unclear if this ability extends to rats. The present studies investigate the prosocial decision-making behavior of female rats in response to the prior actions of another rat in both triadic and dyadic social contexts. In Experiment One, an "actor" rat repeatedly pressed a lever to open a restrainer door, enabling a trapped conspecific to access food. Consistent with reciprocity, when the roles were reversed, the previously trapped conspecific helped the actor. In Experiments Two and Three, the actor rat's ability to open the door was manipulated, with some trials where the door was blocked and the actor was unable to open it and some trials where the actor was able to, but rarely opened the door. In the triadic context, the previously trapped rat then had the opportunity to help the actor, a neutral control, both, or neither (Experiment Two). In the dyadic context, the previously trapped rat could then help the actor (Experiment Three). Reciprocity was not observed in the triadic context. However, unexpectedly, relative to a neutral control conspecific, rats showed a stronger preference for the less helpful actor compared to the helpful or unable actor. In contrast, in the dyadic context, rats did show reciprocity and displayed a higher propensity to help the helpful or unable actor compared to the less helpful actor. These findings shed light on rats' complex social behavior and highlight the context-dependent nature of their helping behavior.

Humans are perhaps the most curious animals on earth, but to what extent our innate motivations for discovering new information are shared with our closest relatives remain poorly understood. To shed light on this question, we presented great apes with two experimental paradigms in which they had to initially choose between an empty opaque cup and a baited opaque cup with rewards invisible to the ape in study 1, or to choose between a transparent cup with rewards or a baited opaque cup with rewards invisible to the ape in studies 2 and 3. We also presented young children with scenarios comparable to the second paradigm (studies 4 and 5). Notably, after the initial choice phase, we presented participants with potential alternatives providing better rewards than the previously secured options. Importantly, those alternatives shared some features with the uncertain options, giving subjects the possibility to relate both options through analogical reasoning. We found that most great apes were not curious about the uncertain options. They only explored those options after they were presented with the alternatives. Children, instead, explored the uncertain options before the alternatives were presented, showing a higher degree of curiosity than the great apes. We argue that differences between children and apes mostly lay in motivational dispositions to explore the unknown.

Joint commitment, the feeling of mutual obligation binding participants in a joint action, is typically conceptualized as arising by the expression and acceptance of a promise. This account limits the possibilities of investigating fledgling forms of joint commitment in actors linguistically less well-endowed than adult humans. The feeling of mutual obligation is one aspect of joint commitment (the product), which emerges from a process of signal exchange. It is gradual rather than binary; feelings of mutual obligation can vary in strength according to how explicit commitments are perceived to be. Joint commitment processes are more complex than simple promising, in at least three ways. They are affected by prior joint actions, which create precedents and conventions that can be embodied in material arrangements of institutions. Joint commitment processes also arise as solutions to generic coordination problems related to opening up, maintaining and closing down joint actions. Finally, during joint actions, additional, specific commitments are made piecemeal. These stack up over time and persist, making it difficult for participants to disengage from joint actions. These complexifications open up new perspectives for assessing joint commitment across species. This article is part of the theme issue Revisiting the human interaction engine: comparative approaches to social action coordination.

The Interaction Engine Hypothesis postulates that humans have a unique ability and motivation for social interaction. A crucial juncture in the ontogeny of the interaction engine could be around 2-4 years of age, but observational studies of children in natural contexts are limited. These data appear critical also for comparison with non-human primates. Here, we report on focal observations on 31 children aged 2- and 4-years old in four preschools (10 h per child). Children interact with a wide range of partners, many infrequently, but with one or two close friends. Four-year olds engage in cooperative social interactions more often than 2-year olds and fight less than 2-year olds. Conversations and playing with objects are the most frequent social interaction types in both age groups. Children engage in social interactions with peers frequently (on average 13 distinct social interactions per hour) and briefly (28 s on average) and shorter than those of great apes in comparable studies. Their social interactions feature entry and exit phases about two-thirds of the time, less frequently than great apes. The results support the Interaction Engine Hypothesis, as young children manifest a remarkable motivation and ability for fast-paced interactions with multiple partners. This article is part of the theme issue Revisiting the human interaction engine: comparative approaches to social action coordination.

Animal telemetry is a subject of great potential and scientific interest, but it shows design-dependent problems related to price, flexibility and customization, autonomy, integration of elements, and structural design. The objective of this paper is to provide solutions, from the application of design, to cover the niches that we discovered by reviewing the scientific literature and studying the market. The design process followed to achieve the objective involved a development based on methodologies and basic design approaches focused on the human experience and also that of the animal. We present a modular collar that distributes electronic components in several compartments, connected, and powered by batteries that are wirelessly recharged. Its manufacture is based on 3D printing, something that facilitates immediacy in adaptation and economic affordability. The modularity presented by the proposal allows for adapting the size of the modules to the components they house as well as selecting which specific modules are needed in a project. The homogeneous weight distribution is transferred to the comfort of the animal and allows for a better integration of the elements of the collar. This device substantially improves the current offer of telemetry devices for farming animals, thanks to an animal-centered design process.

Although pointing is sparse, overloaded, and indirect, it allows humans to effectively decode shared information, (ex)change their minds, and plan accordingly. Pointing is an invitation to jointly attend to an object, which triggers the mutual inference between agents of each other’s mind. Relevance is a fundamental assumption underlying all human communication, including pointing. We define relevance as how much a signaler’s belief can make a positive difference to its receiver’s well being. We build a Theory of Mind (ToM) model to test our definition of relevance and use pointing as a case study. In two experiments, we test our relevance model in a classic artificial intelligence (AI) task, the Wumpus world, with the key difference that there is a guide that points to help a hunter. Agents with our relevance model gain significantly higher rewards than agents who ignore signals from the guide. Agents with our model also achieve better performance than agents who receive an additional observation of the environment. The results show that the power of pointing comes from the ToM inference of relevance, rather than providing more precise individual perception.

Human joint action seems special, as it is grounded in joint commitment-a sense of mutual obligation participants feel towards each other. Comparative research with humans and non-human great apes has typically investigated joint commitment by experimentally interrupting joint actions to study subjects' resumption strategies. However, such experimental interruptions are human-induced, and thus the question remains of how great apes naturally handle interruptions. Here, we focus on naturally occurring interruptions of joint actions, grooming and play, in bonobos and chimpanzees. Similar to humans, both species frequently resumed interrupted joint actions (and the previous behaviours, like grooming the same body part region or playing the same play type) with their previous partners and at the previous location. Yet, the probability of resumption attempts was unaffected by social bonds or rank. Our data suggest that great apes experience something akin to joint commitment, for which we discuss possible evolutionary origins.

The ultimatum game (UG) is widely used to investigate our sense of fairness, a key characteristic that differentiates us from our closest living relatives, bonobos and chimpanzees. Previous studies found that, in general, great apes behave as rational maximizers in the UG. Proposers tend to choose self-maximizing offers, while responders accept most non-zero offers. These studies do not rule out the possibility that apes can behave prosocially to improve the returns for themselves and others. However, this has never been well studied. In this study, we offer chimpanzee and bonobo proposers the possibility of taking into account the leverage of responders over the offers they receive. This leverage takes the form of access to alternatives for responders. We find that proposers tend to propose fairer offers when responders have the option to access alternatives. Furthermore, we find that both species use their leverage to reject unequal offers. Our results suggest that great apes mostly act as rational maximizers in an UG, yet access to alternatives can lead them to change their strategies such as not choosing the self-maximizing offer as proposers and not accepting every offer higher than zero as responders.

Many social animals interact jointly, but only humans experience a specific sense of obligation toward their co-participants, a joint commitment. However, joint commitment is not only a mental state but also a process that reveals itself in the coordination efforts deployed during entry and exit phases of joint action. Here, we investigated the presence and duration of such phases in N = 1,242 natural play and grooming interactions of captive chimpanzees and bonobos. The apes frequently exchanged mutual gaze and communicative signals prior to and after engaging in joint activities with conspecifics, demonstrating entry and exit phases comparable to those of human joint activities. Although rank effects were less clear, phases in bonobos were more moderated by friendship compared to phases in chimpanzees, suggesting bonobos were more likely to reflect patterns analogous to human "face management". This suggests that joint commitment as process was already present in our last common ancestor with Pan.

Social primates face conflicts of interest with other partners when their individual and collective interests collide. Despite living in small, primarily bonded, groups compared to other social primates, gibbons are not exempt from these conflicts in their everyday lives. In the current task, we asked whether dyads of gibbons would solve a conflict of interest over food rewards. We presented dyads of gibbons with a situation in which they could decide whether to take an active role and pull a handle to release food rewards at a distance or take a passive role and avoid action. In this situation, the passive partner could take an advantageous position to obtain the rewards over the active partner. Gibbons participated in three conditions: a control condition with no food rewards, a test condition with indirect food rewards and a test condition with direct food rewards. In both test conditions, five rewards were released at a distance from the handle. In addition, the active individual could obtain one extra food reward from the handle in the direct food condition. We found that gibbons acted more often in the two conditions involving food rewards, and waited longer in the indirect compared to the direct food condition, thus suggesting that they understood the task contingencies. Surprisingly, we found that in a majority of dyads, individuals in the active role obtained most of the payoff compared to individuals in the passive role in both food conditions. Furthermore, in some occasions individuals in the active role did not approach the location where the food was released. These results suggest that while gibbons may strategize to maximize benefits in a competitive food task, they often allowed their partners to obtain better rewards. Our results highlight the importance of social tolerance and motivation as drivers promoting cooperation in these species.

The simple gesture of pointing can greatly augment one’s ability to comprehend states of the world based on observations. It triggers additional inferences relevant to one’s task at hand.We model an agent’s update to its belief of the world based on individualobservations using a partially observable Markov decision process (POMDP), a mainstream artificial intelligence (AI) model of how to act rationally according to beliefs formed through observation. On top of that, we model pointing as a communicative act between agents who have a mutual understanding that the pointed observation must be relevant and interpretable. Our model measures “relevance” by defining a Smithian Value of Information (SVI) as the utility improvement of the POMDP agent before and after receiving the pointing. We model that agents calculate SVI by using the cognitivetheory of Smithian helping as a principle of coordinating separate beliefs for action prediction and action evaluation. We then import SVI into rational speech act (RSA) as the utility function of an utterance. These lead us to a pragmatic model of pointing allowing for contextually flexible interpretations. We demonstrate the power of our Smithian pointing model by extending the Wumpus world, a classic AI task where a hunter hunts a monster with only partial observability of the world. We add another agent as a guide who can only help by marking an observation already perceived by the hunter with a pointing or not, without providing new observations or offering any instrumental help. Our results show that this severely limited and overloaded communication nevertheless significantly improves the hunters’ performance. The advantage of pointing is indeed due to a computation of relevance based on Smithian helping, as it disappears completely when the task is too difficult or too easy for the guide to help.

Coordinated hunting is widely observed in animals, and sharing rewards is often considered a major incentive for this success. However, it is unclear what causal roles are played by this reward-sharing mechanism. In order to systematically examine the effects of sharing rewards in animal coordinated hunting, we conduct a suite of modeling experiments using a state-of-the-art multi-agent reinforcement learning algorithm. The models are trained and evaluated with a task that simulates real-world collective hunting. We manipulate four evolutionarily important variables: reward distribution, hunting party size, free-rider problems, and hunting difficulty. Our results indicate that individually rewarded predators outperform predators that share rewards, especially when the hunting is difficult, the group size is large, and the action cost is high. Moreover, predators with shared rewards suffer from the free-rider problem. We conclude that sharing reward is neither necessary nor sufficient for modeling animal coordinated hunting through reinforcement learning.

Joint action is central to human nature, enabling collectives to achieve goals otherwise unreachable by individuals. It is enabled by humans capacity to understand and engage in joint commitments. Joint commitments are evidenced when partners in interrupted joint actions reengage one another. To date, there is no clear evidence whether nonhuman animals understand joint commitment, suggesting that only humans experience it. Here, we revisit this claim by interrupting bonobos engaged in social activities. Bonobos reliably resumed the activity, and the likelihood of resumption was higher for social compared to solitary activities. Furthermore, communicative efforts deployed to suspend and resume social activities varied depending on partners social relationships and interactive roles. Our results suggest that bonobos, like humans, engage in joint commitment and have some awareness of the social consequences of breaking it.

The relationship between language and thought is controversial. One hypothesis is that language fosters habits of processing information that are retained even in non-linguistic domains. In left-branching (LB) languages, modifiers usually precede the head, and real-time sentence comprehension may more heavily rely on retaining initial information in working memory. Here we presented a battery of working memory and short-term memory tasks to adult native speakers of four LB and four right-branching (RB) languages from Africa, Asia and Europe. In working memory tasks, LB speakers were better than RB speakers at recalling initial stimuli, but worse at recalling final stimuli. Our results show that the practice of parsing sentences in specific directions due to the syntax and word order of our native language not only predicts the way we remember words, but also other non-linguistic stimuli.

This study investigated how the presence of others and anticipated distributions for self influence children's fairness-related decisions in two different socio-moral contexts. In the first part, three- and five-year-old children (N = 120) decided between a fair and an unfair wheel of fortune to allocate resources (procedural justice). In the second part, they directly chose between two distributions of resources (distributive justice). While making a decision, each child was either observed by the affected group members (public), alone (private), or no others were introduced (non-social control). Children choose the fair option more often when others were affected (independently of their presence) only in the procedural justice task. These results suggest that using a fair procedure to distribute resources allows young preschoolers to overcome selfish tendencies.

This paper outlines how the focus on how communicative signals might emerge and how the capacity to interpret them might develop, does not yet explain what type of motivation is required to actually deal with those signals. Without the consistent production of appropriate responses to the production of communicative signals, there would be no point in producing any signal. If language is a tool to accomplish things with others, we need to understand what would lead to cooperation. The first step consists in avoiding the blind belief that all cooperation requires some prosocial attitude. A great deal of cooperation can occur while each participant in the interaction is selfishly attempting to maximize their own benefits or minimizing damaging consequences. I describe how different types of turn-taking can be achieved via different levels of cognitive complexity and how interpretive turn-taking requires a great deal of cognitive abilities that great apes possess. Finally, I provide empirical evidence of social manipulation in non-human primates. Given our awareness of the occurrence of social manipulation during cooperation among human adults, it seems necessary to reconsider to what degree human communication and language evolution require unique prosocial motivations.

Several studies have reported on wide-spread contamination of U.S. paper currency with cocaine and to a lesser extent other illicit drugs. Canines are trained and employed to search for and alert to drugs. Canine alert to currency has been used as evidence that currency has been directly involved in illicit drug trafficking to justify currency seizure and forfeiture. This assertion, particularly when the only evidence is based upon canine alert, has been challenged in the courts considering that most currency in circulation is contaminated with cocaine. Comprehensive review of the scientific literature establishes that (i) 67-100% of circulated U.S. currency is contaminated with cocaine ranging from a few nanograms to over one milligram/bill (ii) various biological and environmental parameters impact canine alert to drugs. It is concluded that canine alert to U.S. currency is not sufficiently reliable to determine that currency was directly used in an illicit drug transaction.

Human adults often show a preference for scarce over abundant goods. In this paper, we investigate whether this preference was shared by 4- and 6-year-old children as well as chimpanzees, humans’ nearest primate relative. Neither chimpanzees nor 4-year-olds displayed a scarcity preference, but 6-year-olds did, especially in the presence of competitors. We conclude that scarcity preference is a human-unique preference that develops as humans increase their cognitive skills and social experiences with peers and competitors. We explore different potential psychological explanations for scarcity preference and conclude scarcity preference is based on children's fear of missing out an opportunity, especially when dealing with uncertainty or goods of unknown value in the presence of competitors. Furthermore, the results are in line with studies showing that supply-based scarcity increases the desirability of hedonic goods, suggesting that even as early as 6 years of age humans may use scarce goods to feel unique or special.

Requesting plays a key role in human communication. One can request the same thing in multiple ways (e.g., "Pass the salt" vs. "Could you pass the salt?"). How do speakers determine which request form to produce? And how does this choice affect a recipient's evaluation of a request? Previous analyses of naturalistic conversations suggest that a speaker's "entitlement" -- their expectations that the recipient of a request is able and willing to fulfill it -- can influence their formatting decisions. However, the role of entitlement in format selection has not been tested experimentally, nor is it known how a requester's entitlement impacts a recipient's evaluation of a request form. Across several online experiments, we asked whether manipulations of a speaker's entitlement influenced formatting preferences across requesters and recipients. While requesters robustly "recognized" normative mappings between entitlement and request formatting (Experiment 2), they did not necessarily follow these mappings unprompted (Experiments 1-1b); instead, they tended to produce modal interrogative requests ("Can you do X?"), regardless of entitlement. Recipients, however, systematically modulated their preferences for particular forms as a function of a requester's entitlement (Experiment 3). We also conducted exploratory analyses on the data from each experiment using human-normed judgments about entitlement and other social-interactional variables (e.g., "degree of imposition"); critically, for both Experiments 2 and 3, judgments about a requester's entitlement explained variance in participants' responses above and beyond other variables.

Ownership is a cornerstone of many human societies and can be understood as a cooperative arrangement, where individuals refrain from taking each other's property. Owners can thus trust others to respect their property even in their absence. We investigated this principle in 5- to 7-year-olds (N = 152) from 4 diverse societies. Children participated in a resource task with a peer-partner, where we established ownership by assigning children to one side or the other of an apparatus and by marking resources with colors to help children keep track of them. When retrieving resources in the partner's presence, the majority of children took their own things and respected what belonged to their partner. A proportion of children in all societies also respected ownership in their partner's absence, although the strength of respect varied considerably across societies. We discuss implications for the development of ownership concepts and possible explanations for societal differences.

ABSTRACT Two views claim to account for the origins of great ape gestural forms. On the Leipzig view, gestural forms are ontogenetically ritualised from action sequences between pairs of individuals. On the St Andrews view, gestures are the product of natural selection for shared gestural forms. The Leipzig view predicts within‐ and between‐group differences between gestural forms that arise as a product of learning in ontogeny. The St Andrews view predicts universal gestural forms comprehensible within and between species that arise because gestural forms were a target of natural selection. We reject both accounts and propose an alternative “recruitment view” of the origins of great ape gestures. According to the recruitment view, great ape gestures recruit features of their existing behavioural repertoire for communicative purposes. Their gestures inherit their communicative functions from visual (and sometimes tactile) presentations of familiar and easily recognisable action schemas and states and parts of the body. To the extent that great ape species possess similar bodies, this predicts mutual comprehensibility within and between species – but without supposing that gestural forms were themselves targets of natural selection. Additionally, we locate great ape gestural communication within a pragmatic framework that is continuous with human communication, and make testable predications for adjudicating between the three alternative views. We propose that the recruitment view best explains existing data, and does so within a mechanistic framework that emphasises continuity between human and non‐human great ape communication. [ABSTRACT FROM AUTHOR]

Property as a social "agreement" comprises both a communicative component, in which someone makes a claim that she is entitled to some piece of property, and a cooperative component, in which others in the community respect that claim as legitimate. In the current study, preschool children were (a) given the opportunity to mark some objects as "theirs" (to claim them in the face of other fictitious children who would supposedly enter the room later); and (b) confronted with stickers in various spatial arrangements (e.g., piled up neatly vs. scattered), told that a fictitious child had previously chosen some for herself but had to suddenly leave the room, and then invited first to choose some stickers for themselves and second to identify which stickers had already been claimed by the fictitious child. Five-year-olds but not 3-year-olds were skillful in both of these tasks, demonstrating an understanding of the crucial role of communication in asserting property claims and the crucial role of cooperation in respecting them.