Comprehension of signs by dolphins (Tursiops truncatus)

The authors assessed the ability of 6 captive dolphins (Tursiops truncatus) to comprehend without explicit training 3 human communicative signs (pointing, directed gaze, and replica). Pointing consisted of indicating the target item with the index finger and a fully extended arm. Directed gaze consisted of orienting the head and eyes toward the target item while the rest of the body remained stationary. The replica signal consisted of holding up an exact duplicate of the target item. On the initial series of 12 trials for each condition, 3 dolphins performed above chance on pointing, 2 on gaze, and none for replica. With additional trials, above chance performance increased to 4 dolphins for pointing, 6 for gazing, and 2 for replica. The replica sign seemed to be the most taxing for them (only 2 dolphins achieved results significantly above chance). Taken together, these results indicate that dolphins are able to interpret untrained communicative signs successfully.     

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.     

Children's understanding of communicative intentions in the middle of the second year of life

Two tasks were administered to 40 children aged from 16 to 20 months (mean age = 18;1), to evaluate children's understanding of declarative and informative intention [Behne, T., Carpenter, M., & Tomasello, M. (2005). One-year-olds comprehend the communicative intentions behind gestures in a hiding game. Developmental Science, 8, 492–499; Camaioni, L., Perucchini, P., Bellagamba, F., & Colonnesi, C. (2004). The role of declarative pointing in developing a theory of mind. Infancy, 5, 291–308]. In the first task, children had to respond to the experimenter who pointed at a distal object; in the second task, children had to find a toy in a hiding game after the experimenter indicated the correct location either by pointing or by gazing. In the first task, most children responded to the declarative gesture by “commenting” on the pointed object instead of just looking; however, looking responses were more frequent than commenting responses. In the second task, children chose the correct location of the object significantly more frequently when the informative gesture was the point than when it was the gaze; moreover, there were significantly more correct choices than incorrect choices in the point but not in the gaze condition. Finally, no significant relation was found between tasks. Taken together, the findings support the view that infants’ developing understanding of communicative intention is a complex process in which general cognitive abilities and contextual factors are equally important.     

Sensing sociality in dogs: what may make an interactive robot social?

This study investigated whether dogs would engage in social interactions with an unfamiliar robot, utilize the communicative signals it provides and to examine whether the level of sociality shown by the robot affects the dogs’ performance. We hypothesized that dogs would react to the communicative signals of a robot more successfully if the robot showed interactive social behaviour in general (towards both humans and dogs) than if it behaved in a machinelike, asocial way. The experiment consisted of an interactive phase followed by a pointing session, both with a human and a robotic experimenter. In the interaction phase, dogs witnessed a 6-min interaction episode between the owner and a human experimenter and another 6-min interaction episode between the owner and the robot. Each interaction episode was followed by the pointing phase in which the human/robot experimenter indicated the location of hidden food by using pointing gestures (two-way choice test). The results showed that in the interaction phase, the dogs’ behaviour towards the robot was affected by the differential exposure. Dogs spent more time staying near the robot experimenter as compared to the human experimenter, with this difference being even more pronounced when the robot behaved socially. Similarly, dogs spent more time gazing at the head of the robot experimenter when the situation was social. Dogs achieved a significantly lower level of performance (finding the hidden food) with the pointing robot than with the pointing human; however, separate analysis of the robot sessions suggested that gestures of the socially behaving robot were easier for the dogs to comprehend than gestures of the asocially behaving robot. Thus, the level of sociality shown by the robot was not enough to elicit the same set of social behaviours from the dogs as was possible with humans, although sociality had a positive effect on dog–robot interactions.     

One-year-olds comprehend the communicative intentions behind gestures in a hiding game

This study explored infants' ability to infer communicative intent as expressed in non-linguistic gestures. Sixty children aged 14, 18 and 24 months participated. In the context of a hiding game, an adult indicated for the child the location of a hidden toy by giving a communicative cue: either pointing or ostensive gazing toward the container containing the toy. To succeed in this task children had to do more than just follow the point or gaze to the target container. They also had to infer that the adult's behaviour was relevant to the situation at hand - she wanted to inform them that the toy was inside the container toward which she gestured. Children at all three ages successfully used both types of cues. We conclude that infants as young as 14 months of age can, in some situations, interpret an adult behaviour as a relevant communicative act done for them.     

Apes' and children's understanding of cooperative and competitive motives in a communicative situation

Chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) (Study 1) and 18- and 24-month-old human children (Study 2) participated in a novel communicative task. A human experimenter (E) hid food or a toy in one of two opaque containers before gesturing towards the reward's location in one of two ways. In the Informing condition, she attempted to help the subject find the hidden object by simply pointing to the correct container. In the Prohibiting condition, E held out her arm toward the correct container (palm out) and told the subject firmly 'Don't take this one.' As in previous studies, the apes were at chance in the Informing condition. However, they were above chance in the new Prohibiting condition. Human 18-month-olds showed this same pattern of results, whereas 24-month-olds showed the opposite pattern: they were better in the Informing condition than in the Prohibiting condition. In our interpretation, success in the Prohibiting condition requires subjects to understand E's goal toward them and their behavior, and then to make an inference (she would only prohibit if there were something good in there). Success in the Informing condition requires subjects to understand a cooperative communicative motive - which apparently apes and young infants find difficult.     

Sharing attention and pointing to objects at 12 months: is the intentional stance implied?

The goal of the present research was to assess whether communicative gestures, such as gazing and declarative pointing of 12-month-old infants indicate that infants perceive people as intentional agents, or whether infant communicative behaviors are merely triggered by specific perceptual cues in joint visual attention situations. Two experiments were conducted. In Experiment 1, thirty-two 12-month-olds were conditioned to follow the gaze of a contingently interacting person or object. They were then submitted to a paradigm designed to incite them to initiate communicative gestures to the person or object. The temporal coordination between pointing, gazing, and vocalizations occurred at a significantly higher rate in the Person than in the Object condition. In Experiment 2, the effect of the attentional focus of others on the gaze, points and vocalizations of thirty 12-month-olds was investigated. Infants were assessed in conditions where the experimenter vocalized while looking at the same (In-focus), or a different (Out-of-focus) toy than the infants. Infants who pointed produced more co-occurrences of gaze, vocalizations and points in the Out-of-focus condition than in the In-focus condition. Thus, by 12 months, infants are aware of the attentional state of the person. Discussion centers on the implications of these findings for theories of social and cognitive knowing.     

Cues that chimpanzees do and do not use to find hidden objects

Chimpanzees follow conspecific and human gaze direction reliably in some situations, but very few chimpanzees reliably use gaze direction or other communicative signals to locate hidden food in the object-choice task. Three studies aimed at exploring factors that affect chimpanzee performance in this task are reported. In the first study, vocalizations and other noises facilitated the performance of some chimpanzees (only a minority). In the second study, various behavioral cues were given in which a human experimenter either touched, approached, or actually lifted and looked under the container where the food was hidden. Each of these cues led to enhanced performance for only a very few individuals. In the third study – a replication with some methodological improvements of a previous experiment – chimpanzees were confronted with two experimenters giving conflicting cues about the location of the hidden food, with one of them (the knower) having witnessed the hiding process and the other (the guesser) not. In the crucial test in which a third experimenter did the hiding, no chimpanzee found the food at above chance levels. Overall, in all three studies, by far the best performers were two individuals who had been raised in infancy by humans. It thus seems that while chimpanzees are very good at “behavior reading” of various sorts, including gaze following, they do not understand the communicative intentions (informative intentions) behind the looking and gesturing of others – with the possible exception of enculturated chimpanzees, who still do not understand the differential significance of looking and gesturing done by people who have different knowledge about states of affairs in the world. Received: 8 November 1999 / Accepted after revision: 24 January 2000     

Comprehension of human pointing gestures in horses (Equus caballus)

Twenty domestic horses (Equus caballus) were tested for their ability to rely on different human gesticular cues in a two-way object choice task. An experimenter hid food under one of two bowls and after baiting, indicated the location of the food to the subjects by using one of four different cues. Horses could locate the hidden reward on the basis of the distal dynamic-sustained, proximal momentary and proximal dynamic-sustained pointing gestures but failed to perform above chance level when the experimenter performed a distal momentary pointing gesture. The results revealed that horses could rely spontaneously on those cues that could have a stimulus or local enhancement effect, but the possible comprehension of the distal momentary pointing remained unclear. The results are discussed with reference to the involvement of various factors such as predisposition to read human visual cues, the effect of domestication and extensive social experience and the nature of the gesture used by the experimenter in comparative investigations.     

Apes' use of iconic cues in the object-choice task

In previous studies great apes have shown little ability to locate hidden food using a physical marker placed by a human directly on the target location. In this study, we hypothesized that the perceptual similarity between an iconic cue and the hidden reward (baited container) would help apes to infer the location of the food. In the first two experiments, we found that if an iconic cue is given in addition to a spatial/indexical cue - e.g., picture or replica of a banana placed on the target location - apes (chimpanzees, bonobos, orangutans, gorillas) as a group performed above chance. However, we also found in two further experiments that when iconic cues were given on their own without spatial/indexical information (iconic cue held up by human with no diagnostic spatial/indexical information), the apes were back to chance performance. Our overall conclusion is that although iconic information helps apes in the process of searching hidden food, the poor performance found in the last two experiments is due to apes' lack of understanding of the informative (cooperative) communicative intention of the experimenter.     

Do common ravens (<Emphasis Type="Italic">Corvus corax</Emphasis>) rely on human or conspecific gaze cues to detect hidden food?

The ability of non-human animals to use experimenter-given cues in object-choice tasks has recently gained interest. In such experiments, the location of hidden food is indicated by an experimenter, e.g. by gazing, pointing or touching. Whereas dogs apparently outperform all other species so far tested, apes and monkeys have problems in using such cues. Since only mammalian species have been tested, information is lacking about the evolutionary origin of these abilities. We here present the first data on object-choice tasks conducted with an avian species, the common raven. Ravens are highly competitive scavengers, possessing sophisticated cognitive skills in protecting their food caches and pilfering others’ caches. We conducted three experiments, exploring (i) which kind of cues ravens use for choosing a certain object, (ii) whether ravens use humans’ gaze for detecting hidden food and (iii) whether ravens would find hidden food in the presence of an informed conspecific who potentially provides gaze cues. Our results indicate that ravens reliably respond to humans’ touching of an object, but they hardly use point and gaze cues for their choices. Likewise, they do not perform above chance level in the presence of an informed conspecific. These findings mirror those obtained for primates and suggest that, although ravens may be aware of the gaze direction of humans and conspecifics, they apparently do not rely on this information to detect hidden food.     

Dingoes (Canis dingo) can use human social cues to locate hidden food

There is contention concerning the role that domestication plays in the responsiveness of canids to human social cues, with most studies investigating abilities of recognized domestic dog breeds or wolves. Valuable insight regarding the evolution of social communication with humans might be gained by investigating Australian dingoes, which have an early history of domestication, but have been free-ranging in Australia for approximately 3500–5000 years. Seven ‘pure’ dingoes were tested outdoors by a familiar experimenter using the object-choice paradigm to determine whether they could follow nine human communicative gestures previously tested with domestic dogs and captive wolves. Dingoes passed all cues significantly above control, including the “benchmark” momentary distal pointing, with the exception of gaze only, gaze and point, and pointing from the incorrect location. Dingo performance appears to lie somewhere between wolves and dogs, which suggests that domestication may have played a role in their ability to comprehend human gestures.     

Pointing gestures modulate domestic dogs’ search behavior for hidden objects in a spatial rotation problem

In the spatial domain, domestic dogs are highly inclined to search at the last location where they saw an object disappear and cannot infer that a hidden object has moved imperceptibly from one location to another. In the current study, we examined whether exposure to human social cues modulates dogs’ search behavior for hidden objects. In Experiment 1, twenty dogs were first trained to find an object they saw disappear inside a stationary container in the presence (social group) or absence (non-social group) of pointing gestures. In tests, the containers were rotated 180° around a central axis. The dogs in the non-social group systematically searched at the initial (now incorrect) hiding location, whereas the dogs in the social group chose correctly significantly above chance. In Experiment 2, we tested whether pre-exposure to human pointing has an impact on dogs’ use of gestures. No gestures were given during training and both the social and non-social conditions were administered to each of the ten dogs. In contrast to Experiment 1, the performance of dogs in the social condition dropped significantly and varied substantially from one dog to another. Overall, this study suggests that dogs’ tendency to use human signals is so strong that it even outweighs their spatial bias to search where they saw an object disappear; however, this penchant to use human gestures appears to be dependent on the degree of familiarity of the dog with these signals.     

Fourteen-month-olds know what others experience only in joint engagement

We investigated how 14‐month‐old infants know what others know. In two studies, an infant played with each of two objects in turn while an experimenter was present. Then the experimenter left the room, and the infant played with a third object with an assistant. The experimenter returned, faced all three objects, and said excitedly ‘Look! Can you give it to me?’ In Study 1, the experimenter experienced each of the first two toys in episodes of joint visual engagement (without manipulation) with the infant. In response to her excited request infants gave the experimenter the object she did not know, thus demonstrating that they knew which ones she knew. In Study 2, infants witnessed the experimenter jointly engage around each of the experienced toys with the assistant, from a third‐person perspective. In response to her request, infants did not give the experimenter the object she had not experienced. In combination with other studies, these results suggest that to know what others have experienced 14‐month‐old infants must do more than just perceive others perceiving something; they must engage with them actively in joint engagement.     

Eighteen-month-old human infants show intensive development in comprehension of different types of pointing gestures

This study explored children’s development in comprehending four types of pointing gestures with different familiarity. Our aim was to highlight human infants’ pointing comprehension abilities under the same conditions used for various animal species. Sixteen children were tested longitudinally in a two-choice task from 1 year of age. At the age of 12 and 14 months, infants did not exceed chance level with either of the gestures used. Infants were successful with distal pointing and long cross-pointing at the age of 16 months. By the age of 18 months, infants showed a high success rate with the less familiar gestures (forward cross-pointing and far pointing) as well. Their skills at this older age show close similarity with those demonstrated previously by dogs when using exactly the same testing procedures. Our longitudinal studies also revealed that in a few infants, the ability to comprehend pointing gestures is already apparent before 16 months of age. In general, we found large individual variation. This has been described for a variety of cognitive skills in human development and seems to be typical for pointing comprehension as well.     

Dogs' (Canis familiaris) responsiveness to human pointing gestures

In a series of 3 experiments, dogs (Canis familiaris) were presented with variations of the human pointing gesture: gestures with reversed direction of movement, cross-pointing, and different arm extensions. Dogs performed at above chance level if they could see the hand (and index finger) protruding from the human body contour. If these minimum requirements were not accessible, dogs still could rely on the body position of the signaler. The direction of movement of the pointing arm did not influence the performance. In summary, these observations suggest that dogs are able to rely on relatively novel gestural forms of the human communicative pointing gesture and that they are able to comprehend to some extent the referential nature of human pointing.     

Out of Sight Is Not Out of Mind: Developmental Changes in Infants' Understanding of Visual Perception During the Second Year

Three experiments investigated 14-, 18-, and 24- month-old infants' understanding of visual perception. Infants viewed films in which a protagonist was either able to view the location of a hidden object (Visual Access condition) or was blindfolded when the object location was revealed (No Visual Access condition). When requested to find the object, the protagonist pointed either at the correct location or at the incorrect location. Across experiments, 18-month-olds looked longer at the unexpected action (e.g., person pointing at the incorrect location in the Visual Access condition). By 24 month of age, infants could infer the correct search behavior from gaze alone. These findings suggest that by the middle of the second year of life, infants understand the psychological relation between an observer and an object, even if the object is no longer visible.     

Learning from others in 9‐18‐month‐old infants

The use of an adult as a resource for help and instruction in a problem solving situation was examined in 9, 14, and 18‐month‐old infants. Infants were placed in various situations ranging from a simple means‐end task where a toy was placed beyond infants' prehensile space on a mat, to instances where an attractive toy was placed inside closed transparent boxes that were more or less difficult for the child to open. The experimenter gave hints and modelled the solution each time the infant made a request (pointing, reaching, or showing a box to the experimenter), or if the infant was unable to solve the problem. Infants' success on the problems, sensitivity to the experimenter's modelling, and communicative gestures (requests, co‐occurrence of looking behaviour and requests) were analysed. Results show that older infants had better success in solving problems although they exhibited difficulties in solving the simple means‐end task compared to the younger infants. Moreover, 14‐ and 18‐month‐olds were sensitive to the experimenter's modelling and used her demonstration cues to solve problems. By contrast, 9‐month‐olds did not show such sensitivity. Finally, 9‐month‐old infants displayed significantly fewer communicative gestures toward the adult compared to the other age groups, although in general, all infants tended to increase their frequency of requests as a function of problem difficulty. These observations support the idea that during the first half of the second year infants develop a new collaborative stance toward others. The stance is interpreted as foundational to teaching and instruction, two mechanisms of social learning that are sometime considered as specifically human. Copyright © 2006 John Wiley & Sons, Ltd.     

How dogs know when communication is intended for them

Domestic dogs comprehend human gestural communication in a way that other animal species do not. But little is known about the specific cues they use to determine when human communication is intended for them. In a series of four studies, we confronted both adult dogs and young dog puppies with object choice tasks in which a human indicated one of two opaque cups by either pointing to it or gazing at it. We varied whether the communicator made eye contact with the dog in association with the gesture (or whether her back was turned or her eyes were directed at another recipient) and whether the communicator called the dog's name (or the name of another recipient). Results demonstrated the importance of eye contact in human-dog communication, and, to a lesser extent, the calling of the dog's name--with no difference between adult dogs and young puppies--which are precisely the communicative cues used by human infants for identifying communicative intent. Unlike human children, however, dogs did not seem to comprehend the human's communicative gesture when it was directed to another human, perhaps because dogs view all human communicative acts as directives for the recipient.     

Two‐year‐olds use adults' but not peers' points

In the current study, 24‐ to 27‐month‐old children (N = 37) used pointing gestures in a cooperative object choice task with either peer or adult partners. When indicating the location of a hidden toy, children pointed equally accurately for adult and peer partners but more often for adult partners. When choosing from one of three hiding places, children used adults’ pointing to find a hidden toy significantly more often than they used peers’. In interaction with peers, children's choice behavior was at chance level. These results suggest that toddlers ascribe informative value to adults’ but not peers’ pointing gestures, and highlight the role of children's social expectations in their communicative development.