A Comparative Study of the Use of Visual Communicative Signals in Interactions Between Dogs (Canis familiaris) and Humans and Cats (Felis catus) and Humans.

Dogs' (Canis familiaris) and cats' (Felis catus) interspecific communicative behavior toward humans was investigated. In Experiment 1, the ability of dogs and cats to use human pointing gestures in an object-choice task was compared using 4 types of pointing cues differing in distance between the signaled object and the end of the fingertip and in visibility duration of the given signal. Using these gestures, both dogs and cats were able to find the hidden food; there was no significant difference in their performance. In Experiment 2, the hidden food was made inaccessible to the subjects to determine whether they could indicate the place of the hidden food to a naive owner. Cats lacked some components of attention-getting behavior compared with dogs. The results suggest that individual familiarization with pointing gestures ensures high-level performance in the presence of such gestures; however, species-specific differences could cause differences in signaling toward the human. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chimpanzees (Pan troglodytes) conceal visual and auditory information from others.

Chimpanzees (Pan troglodytes) competed with a human for food. The human sat inside a booth, with 1 piece of food to her left and 1 to her right, which she could retract from her chimpanzee competitor's reach as needed. In Experiment 1, chimpanzees could approach either side of the booth unseen but then had to reach through 1 of 2 tunnels (1 clear, 1 opaque) for the food. In Experiment 2, both tunnels were clear and the human was looking away, but 1 of the tunnels made a loud noise when it was opened. Chimpanzees preferentially reached through the opaque tunnel in the first study and the silent tunnel in the second, successfully concealing their taking of the food from the human competitor in both cases. These results suggest that chimpanzees can, in some circumstances, actively manipulate the visual and auditory perception of others by concealing information from them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of experimenter-given manual and facial cues by gorillas (Gorilla gorilla) in an object-choice task.

Captive lowland gorillas (Gorilla gorilla) were tested for their ability to use experimenter-given manual and facial cues in an object-choice task. Performance levels were high when the experimenter tapped on or pointed at an object that contained a reward. Performance remained good when the experimenter withheld manual gestures and instead gazed with eyes and head oriented toward the correct object. In contrast, when only the experimenter's eye orientation served as the cue, the gorillas did not appropriately complete the task. Repeated attempts to establish prolonged mutual eye contact with 1 gorilla failed. The gorillas' failure to use eye signals as a cue may be due to an aversion to direct eye contact and contrasts with findings in other great apes. The results may indicate a difference among great ape species in detection of intentionality, but an alternative interpretation is that performance in such tests is influenced by factors such as rearing experience and temperament. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Grunt communication in human infants (Homo sapiens).

Laryngeally produced vocalizations termed grunts function communicatively in many species. The vocalizations and accompanying behavior of 5 human infants videorecorded monthly at the transition to speech were analyzed to determine the frequency, physiological basis, and functional status of grunt production, a phenomenon systematically studied for the first time here. Earliest grunts occurred accompanying movement or effort; next, they accompanied acts of focal attention; and finally they were used in communication. Communicative use was followed by the onset of referential ability in language. This sequence is interpreted in relation to the physiological basis of these vocalizations in respiratory function and to additional developmental variables observed in the children. The findings have implications for the transition to the communicative repertoire in other species in which laryngeal function contributes to communication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Communication of oral deaf and normally hearing children at 36 months of age

Eighteen orally educated deaf and 18 normally hearing 36-month-old children were observed in a play session with their mother. Communicative behavior of the child was coded for modality and communicative function. Although the oral deaf children used a normal range of functions, both the quantity and proportions differed from normally hearing children. Whereas the normally hearing 3-year-olds used speech almost exclusively, the deaf children exhibited about equal use of speech, vocalizations, and gestures. Spoken language scores of the deaf children at 5 years of age were best predicted by (a) more frequent use of speech at age 36 months, (b) more frequent use of the Statement function, and (c) relatively infrequent use of the Directive function. It is suggested that some communicative functions are more informative or heuristic than others, and that the early use of these functions is most likely to predict later language competence.     

Imitative learning of artificial fruit processing in children (Homo sapiens) and chimpanzees (Pan troglodytes).

Observational learning in chimpanzees and young children was investigated using an artificial fruit designed as an analog of natural foraging problems faced by primates. Each of 3 principal components could be removed in 2 alternative ways, demonstration of only one of which was watched by each subject. This permitted subsequent imitation by subjects to be distinguished from stimulus enhancement. Children aged 2–4 years evidenced imitation for 2 components, but also achieved demonstrated outcomes through their own techniques. Chimpanzees relied even more on their own techniques, but they did imitate elements of 1 component of the task. To our knowledge, this is the first experimental evidence of chimpanzee imitation in a functional task designed to simulate foraging behavior hypothesized to be transmitted culturally in the wild. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Referential Communication by Chimpanzees (Pan troglodytes).

Two experiments were conducted to assess the referential function of chimpanzee (Pan troglodytes) gestures to obtain food. The chimpanzees received 1 trial per condition. In Experiment 1 (N = 101), in full view of the chimpanzee, a banana was placed on top of 1 of 2 inverted buckets or was hidden underneath 1 of the buckets. In Experiment 2 (N = 35), 4 conditions were presented in constant order: (a) no food, no observer; (b) no food, observer present; (c) food present, no observer; and (d) food present, observer present. Gestures and visual orienting were used socially and referentially. The capacity for nonverbal reference may predate the Hominidae-Pongidae split, and the development of nonverbal reference may be independent of human species-specific adaptations for speech. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

New evidence on imitation in an enculturated chimpanzee (Pan troglodytes).

Imitation in the great apes continues to be an active field of research and one that is not free of controversy. Several studies suggest that these species do not tend to match the motor movements of the model they observe, but try to achieve the same results using their own methods (emulation of results). In the studies reviewed, gestures have been used very infrequently outside an intraspecific communicative context to evaluate imitation. In fact, the imitation of gestural actions has been tested only in 4 individual great apes. This study assessed a chimpanzee’s (Pan troglodytes) ability to imitate 52 actions in 4 categories. The levels of accuracy attained by the subject in her imitations exceeded those described in previous studies. Moreover, contrary to the idea defended in some articles, the subject seemed to find it easier to imitate gestures than actions with objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recent use of signs by chimpanzees (Pan troglodytes) in interactions with humans.

In light of the controversy about the linguistic properties of chimpanzee signing behavior, the recent sign use of 5 chimpanzees (Pan troglodytes) with long histories of sign use was analyzed while they interacted with longtime human companions. Four corpora from 1992 to 1999 consisting of 3,448 sign utterances were examined. The chimpanzees predominantly used object and action signs. There was no evidence for semantic or syntactic structure in combinations of signs. Longer combinations showed repetition and stringing of object and action signs. The chimpanzees mostly signed with an acquisitive motivation. Requests for objects and actions were the predominant communicative intentions of the sign utterances, though naming and answering also occurred. This recent sign use shows multiple differences with (early) human language. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral laterality in captive bonobos (Pan paniscus).

Behavioral laterality was studied in a captive group of 11 bonobos (Pan paniscus). In an observational method a significant left lateral bias in carrying and a right lateral bias in leading limb were found. Direction of lateral bias in carrying and leading limb was enhanced when Ss maintained a bipedal posture. Analysis of bimanual feeding behavior revealed a significant right-hand bias for eating when the Ss were holding food with their left hand. In an experimental method a significant shift toward greater right-hand use was found when Ss were required to maintain a bipedal, rather than a quadrupedal, posture. There was no evidence of lateral bias for measures of face touching, self-touching, or gestures. The results are discussed in the context of previous reports of primate laterality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hand use and gestural communication in chimpanzees (Pan troglodytes).

Hand use in gestural communication was examined in 115 captive chimpanzees (Pan troglodytes). Hand use was measured in subjects while they gestured to food placed out of their reach. The distribution of hand use was examined in relation to sex, age, rearing history, gesture type, and whether the subjects vocalized while gesturing. Overall, significantly more chimpanzees, especially females and adults, gestured with their right than with their left hand. Foods begs were more lateralized to the right hand than pointing, and a greater prevalence of right-hand gesturing was found in subjects who simultaneously vocalized than those who did not. Taken together, these data suggest that referential, intentional communicative behaviors, in the form of gestures, are lateralized to the left hemisphere in chimpanzees. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dogs' ( Canis familaris ) responsiveness to human pointing gestures.

In a series of 3 experiments, dogs (Canisfamiliaris) 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right-handedness predominance in 162 baboons (Papio anubis) for gestural communication: Consistency across time and groups.

Whether nonhuman primates exhibit population level right manual bias remains a controversial topic. In captive baboons, population-level right-handedness has been reported for both coordinated bimanual actions and communicative gestures. However, some authors remain skeptical of these findings on both methodological and theoretical grounds. Here, we demonstrated the robustness and the consistency across time of the pattern of right-handedness for a species-specific communicative gesture in olive baboons (Papio anubis). First, we showed significant correlations in the 26 retested baboons for the measures of hand preferences between the first and the second session conducted 4 years later (2005–2009) by an observer blind to the previous handedness data. Second, the replication of the study in 96 novel individuals revealed a similar degree of population-level right-handedness than the one expressed in the first group of 66 subjects investigated in 2005. The implications of the findings are discussed within a theoretical framework about the origin of hemispheric specialization for language. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Social referencing by young chimpanzees (Pan troglodytes).

Social referencing is the seeking of information from another individual and the use of that information to evaluate a situation. It is a well-documented ability in human infants but has not been studied experimentally in nonhuman primates. Seventeen young nursery-reared chimpanzees (14 to 41 months old) were observed in a standard social referencing paradigm in which they received happy and fear messages concerning novel objects from a familiar human caregiver. Each chimpanzee looked referentially at their caregiver, and the emotional messages that they received differentially influenced their gaze behavior and avoidance of the novel objects. It is concluded that chimpanzees can acquire information about their complex social and physical environments through social referencing and can use emotional information to alter their own behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dolphins (Tursiops truncatus) comprehend the referential character of the human pointing gesture.

The authors tested a dolphin's (Tursiops truncatus) understanding of human manual pointing gestures to 3 distal objects located to the left of, to the right of, or behind the dolphin. The human referred to an object through a direct point (Pd), a cross-body point (Px), or a familiar symbolic gesture (S). In Experiment 1, the dolphin responded correctly to 80% of Pds toward laterally placed objects but to only 40% of Pds to the object behind. Responding to objects behind improved to 88% in Experiment 2 after exaggerated pointing was briefly instituted. Spontaneous comprehension of Pxs also was demonstrated. In Experiment 3, the human produced a sequence of 2 Pds, 2 Pxs, 2 Ss, or all 2-way combinations of these 3 to direct the dolphin to take the object referenced second to the object referenced first. Accuracy ranged from 68% to 77% correct (chance?=?17%). These results established that the dolphin understood the referential character of the human manual pointing gesture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When do gestures communicate? A meta-analysis.

Do the gestures that speakers produce while talking significantly benefit listeners' comprehension of the message? This question has been the topic of many research studies over the previous 35 years, and there has been little consensus. The present meta-analysis examined the effect sizes from 63 samples in which listeners' understanding of a message was compared when speech was presented alone with when speech was presented with gestures. It was found that across samples, gestures do provide a significant, moderate benefit to communication. Furthermore, the magnitude of this effect is moderated by 3 factors. First, effects of gesture differ as a function of gesture topic, such that gestures that depict motor actions are more communicative than those that depict abstract topics. Second, effects of gesture on communication are larger when the gestures are not completely redundant with the accompanying speech; effects are smaller when there is more overlap between the information conveyed in the 2 modalities. Third, the size of the effect of gesture is dependent on the age of the listeners, such that children benefit more from gestures than do adults. Remaining questions for future research are highlighted. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Affiliative vocalizations in infant rhesus macaques (Macaca mulatta).

In Exp 1, infant rhesus monkeys were separated and then reunited with mothers, united with a male, or placed into an empty cage. Infants girned more when with mothers or the male than when alone. Girns declined over time when infants were united with the male. Coo rates were high when the infant was alone or with the male. Shrieks, barks, and fear-related behavior were higher with the male. In Exp 2, the vocalizations of infants were examined during separation when alone or when mothers or a male were in the same room. Infants cooed more when mothers or a male were present. Cooing increased over time, with a greater increase in the mothers' presence. Girns were given to both mothers and males, but more were given to mothers. Coos and girns are both affiliative vocalizations but are differentially modulated as infants cease cooing when they receive contact comfort. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of auditory distance cues by black-capped chickadees (Poecile atricapillus) and zebra finches (Taeniopygia guttata).

The authors examined auditory distance perception using a go/no-go operant discrimination task in the laboratory. They taught male black-capped chickadees (Poecile atricapillus) and male zebra finches (Taeniopygia guttata) to discriminate degraded (far) from undegraded (near) versions of male chickadee songs and female zebra finch calls, showing for the 1st time that males can discriminate distance cues in heterospecific vocalizations and in female calls. Chickadees learned faster than zebra finches, and both species learned to discriminate chickadee songs faster than zebra finch calls. Chickadees more than zebra finches attended to amplitude in tests pitting it against other distance cues, demonstrating that amplitude is a potentially useful cue for estimating distance from vocalizations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children's use of mutual exclusivity to learn labels for parts of objects.

When teaching children part terms, adults frequently outline the relevant part rather than simply point. This pragmatic information very likely helps children interpret the label correctly. But the importance of gestures may not negate the need for default lexical biases such as the whole object assumption and mutual exclusivity. On this view, children initially assume that a novel label refers to a whole object. If the label for the object is familiar, mutual exclusivity blocks this assumption and frees children to look for a part referent. In this study, the authors taught children part terms by outlining a novel part of a real object. We made mutual exclusivity available by showing children familiar whole objects with novel parts and unavailable by showing unfamiliar whole objects with novel parts. During test, the object was oriented with the part facing away from the child to distinguish pointing to the object from pointing to the part. Both 2-year-olds and 3-year-olds learned more part labels when mutual exclusivity was available. Thus, mutual exclusivity is indispensable even when part labeling is accompanied by naturalistic communicative gestures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trading behavior between conspecifics in chimpanzees, Pan troglodytes.

Bartering of commodities between individuals is a hallmark of human behavior that is not commonly seen in other species. This is difficult to explain because barter is mutually beneficial and appears to be within the cognitive capabilities of many species. It may be that other species do not recognize the gains of trade, or that they do not experience conditions (e.g., low risk) in which barter is most beneficial. To answer these questions, the authors instituted a systematic study of chimpanzees’ ability to barter with each other when doing so materially benefited them. Using tokens derived from symbols they had used since infancy, pairs of adult chimpanzees (Pan troglodytes) could trade between themselves to obtain tokens needed to get foods. Chimpanzees flexibly used the tokens to obtain foods from an experimenter; however, they did not spontaneously trade with their partner. After extensive training, chimpanzees engaged in accurate trade behavior as long as an experimenter enforced the structure of the interaction; however, trade between partners disappeared when this enforcement was removed. The authors discuss possible reasons for these findings as well as implications for the evolution of barter across the primate lineage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)