Kim A. Bard

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.

Observational learning of tool-use by young chimpanzees

In the current study two groups of young chimpanzees (4–6 and 8–9 years old) were given a T-bar and a food item that could only be reached by using the T-bar. Experimental subjects were given the opportunity to observe an adult using the stick as a tool to obtain the food; control subjects were exposed to the adult but were given no demonstration. Subjects in the older group did not learn to use the tool. Subjects in the younger group who were exposed to the demonstrator learned to use the stick as a tool much more readily than those who were not. None of the subjects demonstrated an ability to imitatively copy the demonstrators precise behavioral strategies. More than simple stimulus enhancement was involved, however, since both groups manipulated the T-bar, but only experimental subjects used it in its function as a tool. Our findings complement naturalistic observations in suggesting that chimpanzee tool-use is in some sense «culturally transmitted» — though perhaps not in the same sense as social-conventional behaviors for which precise copying of conspecifics is crucial.

Orientation to social and nonsocial stimuli in neonatal chimpanzees and humans

Abstract The behavioral capabilities of neonatal chimpanzees are not well known. A major goal of this study was to document their ability to orient to social and nonsocial objects and to compare their performance with that of human infants. The Brazelton Neonatal Behavioral Assessment Scale (NBAS) was administered to 13 nursery-reared chimpanzees, every other day during their first month of life, and to 42 humans, twice, on the third and thirtieth day of life. The orientation items included social stimuli (a human face and both human and chimpanzee sounds) and nonsocial stimuli (a red ball and a red rattle). Repeated-measures analysis of variance on the orientation cluster of the NBAS revealed that chimpanzee neonates have the capacity for sustained attention to all stimuli, both social and nonsocial, indistinguishable from that of human neonotes. Significant improvements in orientation performance from Day 2 to Day 30 were found for both species. These striking similarities in early orientation ability are viewed as a challenge to notions of unique human propensities.

Understanding the Point of Chimpanzee Pointing: Epigenesis and Ecological Validity

Pointing has long been considered to be a uniquely human, universal, and biologically based gesture. However, pointing emerges spontaneously, without explicit training, in captive chimpanzees. Because pointing is commonplace in captive chimpanzees and virtually absent in wild chimpanzees, and because both captive and wild chimpanzees are sampled from the same gene pool, pointing by captive apes is attributable to environmental influences on communicative development. If pointing by captive chimpanzees is so variably expressed in different rearing environments, this suggests that pointing by humans may also be attributable to situational factors that make pointing effective in certain developmental contexts.

Chimpanzee hand preference for throwing and infant cradling:implications for the origin of human handedness

Calvin (i983) has hypothesized that the neurophysiological, perceptual, and cognitive demands of throwing may have served as important evolutionary precursors to a variety of traits( e.g., handedness, tool use, and language processing) in early hominids. Eighty-eight percent of humans throw with their right hands (Healey, Liederman, and Geschwind I986), and Calvin has argued that this right-handed throwing evolved as a result of a left-hemisphere specialization for planned sequential movements. He has further suggested that right-handed throwing would have been more prevalent in females than in males because females predominantly carried infants on the left arm, leaving the right hand available for other actions. Infant carrying has also been hypothesized as a major selective feature in the evolution of bipedalism in hominids (Leakey I976).

Group differences in the mutual gaze of chimpanzees (Pan troglodytes).

A comparative developmental framework was used to determine whether mutual gaze is unique to humans and, if not, whether common mechanisms support the development of mutual gaze in chimpanzees and humans. Mother-infant chimpanzees engaged in approximately 17 instances of mutual gaze per hour. Mutual gaze occurred in positive, nonagonistic contexts. Mother-infant chimpanzees at a Japanese center exhibited significantly more mutual gaze than those at a center in the United States. Cradling and motor stimulation varied across groups. Time spent cradling infants was inversely related to mutual gaze. It is suggested that in primates, mutual engagement is supported via an interchangeability of tactile and visual modalities. The importance of mutual gaze is best understood within a perspective that embraces both cross-species and cross-cultural data.

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.

Towards an Affect Space for robots to display emotional body language

In order for robots to be socially accepted and generate empathy it is necessary that they display rich emotions. For robots such as Nao, body language is the best medium available given their inability to convey facial expressions. Displaying emotional body language that can be interpreted whilst interacting with the robot should significantly improve its sociability. This research investigates the creation of an Affect Space for the generation of emotional body language to be displayed by robots. To create an Affect Space for body language, one has to establish the contribution of the different positions of the joints to the emotional expression. The experiment reported in this paper investigated the effect of varying a robots head position on the interpretation, Valence, Arousal and Stance of emotional key poses. It was found that participants were better than chance level in interpreting the key poses. This finding confirms that body language is an appropriate medium for robot to express emotions. Moreover, the results of this study support the conclusion that Head Position is an important body posture variable. Head Position up increased correct identification for some emotion displays (pride, happiness, and excitement), whereas Head Position down increased correct identification for other displays (anger, sadness). Fear, however, was identified well regardless of Head Position. Head up was always evaluated as more highly Aroused than Head straight or down. Evaluations of Valence (degree of negativity to positivity) and Stance (degree to which the robot was aversive to approaching), however, depended on both Head Position and the emotion displayed. The effects of varying this single body posture variable were complex.

Development of manipulations with objects in ape and human infants

Object manipulations were studied in infants (8–11 months of age) of three primate species: human; common chimpanzee ( Pan troglodytes ); and bonobo or pygmy chimpanzee ( Pan paniscus ). Observations of free play were videotaped and the complexity of manipulations (based on Piagetian theory) and functional usage of modes (both hands and feet) was described. Results indicated that the chimpanzee mouthed (without grasping) more frequently than both the bonobo and human infants. For all infants, half of the object-oriented behaviors consisted of active manipulations of a single object. However, for the apes, most of these manipulations consisted of simple holding and/or moving the objects against a substrate. In contrast, the human infant more frequently extracted an object from the background and, furthermore, moved the object or explored its unique characteristics. Additionally, the human infant exhibited a richness and differentation in the use of modes that was not observed in ape infants. These results are discussed within an evolutionary perspective.

Classifying Chimpanzee Facial Expressions Using Muscle Action

The Chimpanzee Facial Action Coding System (ChimpFACS) is an objective, standardized observational tool for measuring facial movement in chimpanzees based on the well-known human Facial Action Coding System (FACS; P. Ekman & W. V. Friesen, 1978). This tool enables direct structural comparisons of facial expressions between humans and chimpanzees in terms of their common underlying musculature. Here the authors provide data on the first application of the ChimpFACS to validate existing categories of chimpanzee facial expressions using discriminant functions analyses. The ChimpFACS validated most existing expression categories (6 of 9) and, where the predicted group memberships were poor, the authors discuss potential problems with ChimpFACS and/or existing categorizations. The authors also report the prototypical movement configurations associated with these 6 expression categories. For all expressions, unique combinations of muscle movements were identified, and these are illustrated as peak intensity prototypical expression configurations. Finally, the authors suggest a potential homology between these prototypical chimpanzee expressions and human expressions based on structural similarities. These results contribute to our understanding of the evolution of emotional communication by suggesting several structural homologies between the facial expressions of chimpanzees and humans and facilitating future research.