A comparative analysis of animals' understanding of the human pointing gesture

Dogs catch human yawns

This study is the first to demonstrate that human yawns are possibly contagious to domestic dogs (Canis familiaris). Twenty-nine dogs observed a human yawning or making control mouth movements. Twenty-one dogs yawned when they observed a human yawning, but control mouth movements did not elicit yawning from any of them. The presence of contagious yawning in dogs suggests that this phenomenon is not specific to primate species and may indicate that dogs possess the capacity for a rudimentary form of empathy. Since yawning is known to modulate the levels of arousal, yawn contagion may help coordinate dog-human interaction and communication. Understanding the mechanism as well as the function of contagious yawning between humans and dogs requires more detailed investigation.

The response of guide dogs and pet dogs (Canis familiaris) to cues of human referential communication (pointing and gaze)

The study raises the question of whether guide dogs and pet dogs are expected to differ in response to cues of referential communication given by their owners; especially since guide dogs grow up among sighted humans, and while living with their blind owners, they still have interactions with several sighted people. Guide dogs and pet dogs were required to respond to point, point and gaze, gaze and control cues of referential communication given by their owners. Results indicate that the two groups of dogs do not differ from each other, revealing that the visual status of the owner is not a factor in the use of cues of referential communication. Both groups of dogs have higher frequencies of performance and faster latencies for the point and the point and gaze cues as compared to gaze cue only. However, responses to control cues are below chance performance for the guide dogs, whereas the pet dogs perform at chance. The below chance performance of the guide dogs may be explained by a tendency among them to go and stand by the owner. The study indicates that both groups of dogs respond similarly in normal daily dyadic interaction with their owners and the lower comprehension of the human gaze may be a less salient cue among dogs in comparison to the pointing gesture.

Attention to attention in domestic dog (Canis familiaris) dyadic play

The social cognitive capacities of dogs, including their communication skills and use of visual attention cues, have recently been investigated in numerous experimental studies. This paper reports on research of domestic dog behavior in a natural setting, which shows sensitivity to the visual attention of their partners when engaged in dyadic rough-and-tumble play. The sequential behaviors and head-direction of both dogs were noted throughout the bouts. The behaviors were differentially used according to the partner's posture. Play signals were sent nearly exclusively to forward-facing conspecifics; attention-getting behaviors were used most often when a playmate was facing away, and before signaling an interest to play. In addition, the mode of attention-getter matched the degree of inattentiveness of the playmate: stronger attention-getters were used when a playmate was looking away or distracted, less forceful ones when the partner was facing forward or laterally. In other words, these dogs showed attention to, and acted to manipulate, a feature of other dogs that mediates their ability to respond: which feature in human interaction is called "attention".

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.

Comprehension of human pointing gestures in young human-reared wolves (Canis lupus) and dogs (Canis familiaris)

Dogs have a remarkable skill to use human-given cues in object-choice tasks, but little is known to what extent their closest wild-living relative, the wolf can achieve this performance. In Study 1, we compared wolf and dog pups hand-reared individually and pet dogs of the same age in their readiness to form eye-contact with a human experimenter in an object-choice task and to follow her pointing gesture. The results showed that dogs already at 4 months of age use momentary distal pointing to find hidden food even without intensive early socialization. Wolf pups, on the contrary, do not attend to this subtle pointing. Accordingly in Studies 2 and 3, these wolves were tested longitudinally with this and four other (easier) human-given cues. This revealed that wolves socialized at a comparable level to dogs are able to use simple human-given cues spontaneously if the human's hand is close to the baited container (e.g. touching, proximal pointing). Study 4 showed that wolves can follow also momentary distal pointing similarly to dogs if they have received extensive formal training. Comparing the wolves to naïve pet dogs of the same age revealed that during several months of formal training wolves can reach the level of dogs in their success of following momentary distal pointing in parallel with improving their readiness to form eye-contact with a human experimenter. We assume that the high variability in the wolves' communicative behaviour might have provided a basis for selection during the course of domestication of the dog.

Association of polymorphisms in the dopamine D4 receptor gene and the activity-impulsivity endophenotype in dogs

A variable number of tandem repeats (VNTR) polymorphism in exon 3 of the human dopamine D4 receptor gene (DRD4) has been associated with attention deficit hyperactivity disorder (ADHD). Rodents possess no analogous repeat sequence, whereas a similar tandem repeat polymorphism of the DRD4 gene was identified in dogs, horses and chimpanzees. Here, we present a genetic association study of the DRD4 VNTR and the activity-impulsivity dimension of the recently validated dog-ADHD Rating Scale. To avoid false positives arising from population stratification, a single breed of dogs (German shepherd) was studied. Two DRD4 alleles (referred to as 2 and 3a) were detected in this breed, and genotype frequencies were in Hardy-Weinberg equilibrium. For modelling distinct environmental conditions, 'pet' and 'police' German shepherds were characterized. Police German shepherds possessing at least one 3a allele showed significantly higher scores in the activity-impulsivity dimension of the dog-ADHD Rating Scale than dogs without this allele (P = 0.0180). This difference was not significant in pet German shepherds. To the best of our knowledge, this is the first report of an association between a candidate gene and a behaviour trait in dogs, and it reinforces the functional role of DRD4 exon 3 polymorphism.

Do common ravens (Corvus corax) 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.

Rhesus monkeys correctly read the goal-relevant gestures of a human agent

When humans point, they reveal to others their underlying intent to communicate about some distant goal. A controversy has recently emerged based on a broad set of comparative and phylogenetically relevant data. In particular, whereas chimpanzees (Pan troglodytes) have difficulty in using human-generated communicative gestures and actions such as pointing and placing symbolic markers to find hidden rewards, domesticated dogs (Canis familiaris) and silver foxes (Urocyon cinereoargenteus) readily use such gestures and markers. These comparative data have led to the hypothesis that the capacity to infer communicative intent in dogs and foxes has evolved as a result of human domestication. Though this hypothesis has met with challenges, due in part to studies of non-domesticated, non-primate animals, there remains the fundamental question of why our closest living relatives, the chimpanzees, together with other non-human primates, generally fail to make inferences about a target goal of an agent's communicative intent. Here, we add an important wrinkle to this phylogenetic pattern by showing that free-ranging rhesus monkeys (Macaca mulatta) draw correct inferences about the goals of a human agent, using a suite of communicative gestures to locate previously concealed food. Though domestication and human enculturation may play a significant role in tuning up the capacity to infer intentions from communicative gestures, these factors are not necessary.

Is your choice my choice? The owners' effect on pet dogs' (Canis lupus familiaris) performance in a food choice task

This study investigates the influence of owners on their dogs' performance in a food choice task using either different or equal quantities of food. Fifty-four pet dogs were tested in three different conditions. In Condition 1 we evaluated their ability to choose between a large and small amount of food (quantity discrimination task). In Condition 2 dogs were again presented with a choice between the large and small food quantity, but only after having witnessed their owner favouring the small quantity. In Condition 3 dogs were given a choice between two equally small quantities of food having witnessed their owner favouring either one or the other. A strong effect of the owner on the dogs' performance was observed. In Condition 1 dogs as a group chose significantly more often the large food quantity, thus showing their ability to solve the quantity discrimination task. After observing their owner expressing a preference for the small food quantity they chose the large quantity of food significantly less than in the independent choice situation. The tendency to conform to the owner's choice was higher when the dogs had to choose between equally small quantities of food (Condition 3) rather than between a large and a small one (Condition 2). These results provide evidence that dogs can be influenced by their owners even when their indications are clearly in contrast with direct perceptual information, thus leading dogs to ultimately make counterproductive choices.

Modifying the object-choice task: is the way you look important for ravens?

Most animals seem to have difficulties in using gaze cues to find hidden food in object-choice tasks. For instance, chimpanzees usually fail in these tests, even though they are capable of following other's gaze geometrically behind barriers. Similar to chimpanzees, common ravens are skilled in tracking other's gaze but fail in object-choice tasks. We here explored whether procedural modifications, which had been used successfully in chimpanzees, would also yield positive results in ravens. In our modifications (a) the experimenter approached the cup while gazing at it, (b) the gaze cue was accompanied by a sound and (c) the experimenter could actually see the food while giving the gaze cue. Two out of seven birds performed above chance level in some of these conditions. However, we ascribe this improvement to the individuals' learning ability rather than to an understanding of the communicative nature of the task. This interpretation is further supported by results of a follow-up experiment suggesting that ravens may not rely on conspecifics' gaze cues for finding food caches in a natural foraging context. In sum, our results suggest that ravens may not transfer their gaze follow abilities to foraging situations involving hidden food.

Behavioral cues that great apes use to forage for hidden food

We conducted three studies to examine whether the four great ape species (chimpanzees, bonobos, gorillas, and orangutans) are able to use behavioral experimenter-given cues in an object-choice task. In the subsequent experimental conditions subjects were presented with two eggs, one of which contained food and the other did not. In Study 1 the experimenter examined both eggs by smelling or shaking them, but only made a failed attempt to open (via biting) the egg containing food. In a control condition, the experimenter examined and attempted to open both eggs, but in reverse order to control for stimulus enhancement. The apes significantly preferred the egg that was first examined and then bitten, but had no preference in a baseline condition in which there were no cues. In Study 2, we investigated whether the apes could extend this ability to cues not observed in apes so far (i.e., attempting to pull apart the egg), as well as whether they made this discrimination based on the function of the action the experimenter performed. Subjects significantly preferred eggs presented with this novel cue, but did not prefer eggs presented with a novel but functionally irrelevant action. In Study 3, apes did not interpret human actions as cues to food-location when they already knew that the eggs were empty. Thus, great apes were able to use a variety of experimenter-given cues associated with foraging actions to locate hidden food and thereby were partially sensitive to the general purpose underlying these actions.

A New Look at Infant Pointing

The current article proposes a new theory of infant pointing involving multiple layers of intentionality and shared intentionality. In the context of this theory, evidence is presented for a rich interpretation of prelinguistic communication, that is, one that posits that when 12-month-old infants point for an adult they are in some sense trying to influence her mental states. Moreover, evidence is also presented for a deeply social view in which infant pointing is best understood--on many levels and in many ways--as depending on uniquely human skills and motivations for cooperation and shared intentionality (e.g., joint intentions and attention with others). Children's early linguistic skills are built on this already existing platform of prelinguistic communication.

Pointing Behaviors in Apes and Human Infants: A Balanced Interpretation

This article presents a tentatively "balanced" view (i.e., midway between lean and rich interpretations) of pointing behavior in infants and apes, based upon the notion of intentional reading of behavior without simultaneous attribution of unobservable mental states. This can account for the complexity of infant pointing without attributing multilayered mindreading to infants. It can also account for ape pointing, which shares some of the complexities of infant pointing, but departs from it in other respects, notably in its range of motives and its focus upon the regulation of executive behavior. The article explores some explanations for these similarities and differences and calls for a new look at human infant communication unbiased by adult communication models.

Selective imitation in domestic dogs

The transmission of cultural knowledge requires learners to identify what relevant information to retain and selectively imitate when observing others' skills. Young human infants--without relying on language or theory of mind--already show evidence of this ability. If, for example, in a communicative context, a model demonstrates a head action instead of a more efficient hand action, infants imitate the head action only if the demonstrator had no good reason to do so, suggesting that their imitation is a selective, interpretative process [1]. Early sensitivity to ostensive-communicative cues and to the efficiency of goal-directed actions is thought to be a crucial prerequisite for such relevance-guided selective imitation [2]. Although this competence is thought to be human specific [2], here we show an analog capacity in the dog. In our experiment, subjects watched a demonstrator dog pulling a rod with the paw instead of the preferred mouth action. In the first group, using the "inefficient" action was justified by the model's carrying of a ball in her mouth, whereas in the second group, no constraints could explain the demonstrator's choice. In the first trial after observation, dogs imitated the nonpreferred action only in the second group. Consequently, dogs, like children, demonstrated inferential selective imitation.

Reproducing human actions and action sequences: "Do as I Do!" in a dog

We present evidence that a dog (Philip, a 4-year-old tervueren) was able to use different human actions as samples against which to match his own behaviour. First, Philip was trained to repeat nine human-demonstrated actions on command ('Do it!'). When his performance was markedly over chance in response to demonstration by one person, testing with untrained action sequences and other demonstrators showed some ability to generalise his understanding of copying. In a second study, we presented Philip with a sequence of human actions, again using the 'Do as I do' paradigm. All demonstrated actions had basically the same structure: the owner picked up a bottle from one of six places; transferred it to one of the five other places and then commanded the dog ('Do it!'). We found that Philip duplicated the entire sequence of moving a specific object from one particular place to another more often than expected by chance. Although results point to significant limitations in his imitative abilities, it seems that the dog could have recognized the action sequence, on the basis of observation alone, in terms of the initial state, the means, and the goal. This suggests that dogs might acquire abilities by observation that enhance their success in complex socio-behavioural situations.