Development In Chimpanzees Research Articles

Triadic relations and emergence of mind in nonhuman primates

When considering the evolutionary origin of language, we should attend to the social-cognitive aspects of language acquisition in addition to the linguistic competence. This view is an emphasis of Bruner's “Language Acquisition Supporting System (LASS)” and recently intensively studied from the comparative-cognitive-developmental perspective. In this article, I summarize the research project of cognitive development in chimpanzees at the Primate Research Institute, Kyoto University (CDC2000), with special reference to the development of social cognition. During the early infancy, chimpanzee infants showed developmental trajectories similar to human infants. Especially, the chimpanzee infants established close dyadic relationship with their mothers on the basis of mutual gaze and social smiling. However, triadic interactions on the basis of sharing attention, more important social interactions for humans, were not observed in chimpanzees even at their juvenile period. This difference in social interactions between humans and chimpanzees may be the source of more critical difference in the understanding of others. Furthermore, the problem of “enculturation” is also discussed in relation to Vygotsky's concept of “zone of proximal development”.

Histologic examination of bone development in juvenile chimpanzees.

The purpose of this study is to determine whether histologic skeletal development in chimpanzees (Pan troglodytes) differs from that in humans. Currently, minimal quantitative data are available on the bone histology of great apes. In addition to providing baseline data on juvenile chimpanzee bone histology, the data generated by this study have potential applications for studying the comparative development between chimpanzees and humans and other primates, as well as investigating the evolution of human bone development, differences in development among limb elements, and differences in histology related to locomotor function. The study sample includes thin sections from the femoral, tibial, and fibular midshafts of 13 chimpanzees originally prepared by Kerley ([1966] Tulane Stud. Zool. 13:71-82) as part of a study on skeletal age changes in the chimpanzee. Twelve juveniles, ranging in known age from 2-15.3 years, and one adult, with a known age of 35 years, are represented. For each specimen, numbers of osteons, osteon fragments, and non-Haversian canals were counted, and percent lamellar bone was estimated. Results were compared with data extracted from Kerley ([1965] Am. J. Phys. Anthropol. 23:149-164) on a juvenile human sample. Results indicate that juvenile chimpanzees and humans exhibit similar age-related changes in histologic variables. However, age is not as strong a predictor of variation in microstructural variables in chimpanzees as it is in humans.

Development of the hand and wrist bones in chimpanzees

Skeletal developmental of chimpanzees was studied cross-sectionally. By application of the TW2 method, we described the skeletal development of chimpanzees and compared their skeletal development with humans'. A development pattern of chimpanzees repeated accelerations and decelerations displaying “early-juvenile trough,” “pre-adolescent peak,” “mid-adolescent trough,” and “post-adolescent peak” in incremental curves. Sex differences in skeletal development are slower development in males during infant and early juvenile phases, and greater increment around the adolescent phase in males. Females are fully mature at younger ages than males, e.g. about one and a half years. In comparison with chimpanzees, humans have such characteristics as a longer slower period of juvenile development and a shorter spurt-like adolescent fast period which ends with full maturity.

Neonatal neurobehavioral correlates of lateral bias and affect in infant chimpanzees (pan troglodytes)

In this study, I extend previous findings of population‐level asymmetries in lateral bias of multiple behavioral measures in infant chimpanzees. Moreover, I propose that different neurobehavioral mechanisms are associated with different behavioral measures. A longitudinal design was employed to assess neonatal neurobehavioral integrity, lateral bias at 3 months old, and lateral bias and affect at 9 to 10 months old. Approximately half of the sample was raised under standard nursery conditions (females, n = 9; males, n = 11), and the other half was raised in a “responsive care” nursery designed to promote species‐typical chimpanzee development (females, n = 9; males, n = 8). Significant right biases were confirmed for hand‐to‐mouth self‐calming behavior. Significant left biases were found in grasping of objects (at 9–10 months old). Hand‐to‐hand grasping, reflexive stepping, head posture while sleeping in a supine position, and defensive swipes were individually lateralized rather than population level biased. Neonatal neurobehavioral assessments were found to be significantly associated with lateral bias both at 3 months and at 9 to 10 months old. Arousal at 2 days of age was negatively correlated with hand‐to‐mouth bias, motor performance at 2 days old was positively correlated with hand‐to‐hand bias, and orientation performance at 30 days of age was positively correlated with head bias. The lateral bias in touching and grasping objects at 9 to 10 months of age was positively correlated with head bias by 3 months of age and with State Regulation at 2 days of age. Affective behavior at 9 to 10 months old was correlated with defensive bias at 3 months and with muscle tone at 2 days of age. Rearing environment, gender, and emotional reactivity were found to influence lateral bias. These findings support the hypothesis that different asymmetric behaviors, even if lateralized to the same direction, may reflect different biological processes and different functional mechanisms.

Differences in Variability, Interactivity and Skills in Social Play of Young Chimpanzees Living in Peer Groups and in a Large Family Zoo Group

Abstract This paper provides a detailed comparison of play characteristics of chimpanzees raised in peer-only groups and in a socially complex semi-natural zoo situation. We expected play in peer groups to be of a lesser quality, that is less variable, interactive and skillful. To test this we quantified details such as the diversity of social play types, the bout length, the way social play is started, maintained and stopped and the use of play signals. The differences in play-type frequencies between the groups are most likely caused by differences in housing conditions and demographics; the smaller sex difference in peer group adolescents is most likely due to a limited partner choice. We found no indication that chimpanzees raised in peer groups played less diversely than those in the zoo. The social play characteristics of peer group and zoo chimpanzees are similar, except for the frequency of gnaws before wrestle and the frequency of play-faces within wrestle. Overall, there are no results from which we can conclude directly that chimpanzees isolated from their mother at an early stage and placed in a peer group are less capable in social play, although possibly it is more clear to the zoo individuals that a next interaction will be 'play'; zoo individuals may need less regular removal of ambiguity about the intention of the behaviour. The few differences between peer group and zoo in their social play characteristics that can be related to peer group rearing conditions indicate that the social development in those chimpanzees raised in peer groups is similar to that of chimpanzees in the semi-natural zoo. This is not to say that providing more natural conditions than is usually done in laboratories is unnecessary. These may still add considerably to the animals' well-being and in terms of animal welfare, it can be concluded that a variety of partners in the housing condition is beneficial to speed of sex-role development in young chimpanzees.

What Young Chimpanzees Know about Seeing

Previous experimental research has suggested that chimpanzees may understand some of the epistemological aspects of visual perception, such as how the perceptual act of seeing can have internal mental consequences for an individual's state of knowledge. Other research suggests that chimpanzees and other nonhuman primates may understand visual perception at a simpler level; that is, they may at least understand seeing as a mental event that subjectively anchors organisms to the external world. However, these results are ambiguous and are open to several interpretations. In this Monograph, we report the results of 15 studies that we conducted with chimpanzees and preschool children to explore their knowledge about visual perception. The central goal of these studies was to determine whether young chimpanzees appreciate that visual perception subjectively links organisms to the external world. In order to achieve this goal, our research incorporated three methodological objectives. First, we sought to overcome limitations of previous comparative theory of mind research by using a fairly large sample of well-trained chimpanzees (six to seven animals in all studies) who were all within 8 months of age of each other. In contrast, previous research has typically relied on the results of one to four animals ranging widely in age. Second, we designed our studies in order to allow for a very sensitive diagnosis of whether the animals possessed immediate dispositions to act in a fashion predicted by a theory of mind view of their psychology or whether their successful performances could be better explained by learning theory. Finally, using fairly well-established transitions in preschool children's understanding of visual perception, we sought to establish the validity of our nonverbal methods by testing predictions about how children of various ages ought to perform. Collectively, our findings provide little evidence that young chimpanzees understand seeing as a mental event. Although our results establish that young chimpanzees both (a) develop algorithms for tracking the visual gaze of other organisms and (b) quickly learn rules about the configurations of faces and eyes, on the one hand, and subsequent events, on the other, they provide no clear evidence that these algorithms and rules are grounded in a matrix of intentionality. Particularly striking, our results demonstrate that, even though young chimpanzee subjects spontaneously attend to and follow the visual gaze of others, they simultaneously appear oblivious to the attentional significance of that gaze. Thus, young chimpanzees possess and learn rules about visual perception, but these rules do not necessarily incorporate the notion that seeing is "about" something. The general pattern of our results is consistent with three different possibilities. First, the potential existence of a general developmental delay in psychological development in chimpanzees (or, more likely, an acceleration in humans) leaves open the possibility that older chimpanzees may display evidence of a mentalistic appreciation of seeing. Second, chimpanzees may possess a different (but nonetheless mentalistic) theory of attention in which organisms are subjectively connected to the world not through any particular sensory modality such as vision but rather through other (as-of-yet unspecified) behavioral indicators. Finally, a subjective understanding of visual perception (and perhaps behavior in general) may be a uniquely evolved feature of the human lineage.

Acquisition and Comprehension of a Tool-Using Behavior by Young Chimpanzees (Pan Troglodytes): Effects of Age and Modeling

Theacquisition of a tool-using ability was investigated in six young chimpanzees (Pan troglodytes, 2 to 4 years old). Age-matched pairs were presented with a horizontal transparent tube with a food item inserted in the center, and a wooden tool. Insertion of the tool into the tube was required in order to obtain the food item. One of each pair was exposed to a model performing the task successfully,whereas the age-matched peer was not. Following acquisition, subjects were tested with more complex versions of the task to evaluate their comprehension. Age affected acquisition; older individuals learned to solve the task in fewer number of trials than younger chimpanzees. The presence of a model influenced acquisition only in the 3-and-4 year-old groups and not in the 2-year-old group. Moreover,older individuals made fewer errors when faced with tools requiring modification, and the performance of older individuals on these complex tasks improved with limited practice. These results are related to recent findings on cognitive development in chimpanzees indicating that self-recognition emerges between 24 and 30 months and that 4 year-old chimpanzees can imitate novel arbitrary actions. Comparisons with human cognitive developmental data and findings on the same task with older apes point to the link between the emergence of imitation, self recognition, and comprehension of the cause-effect relation present in this task. Competence in all these domains is somewhat delayed in chimpanzees compared to humans.

Differences in Play Development of Young Chimpanzees Reared in Family Groups and in Peer Groups

Rhesus and chimpanzee infants reared in family conditions showed higher levels of dominance and activity behaviours than infants reared only with their mother or with peers only. These results suggest that the greater the variety of social partners in a rearing condition, the more the individuals are able to develop social skills that will be advantageous to them in group life. We investigated how living in groups with peers only (n = 65) influenced behaviour development in chimpanzees aged from zero to ten years. Comparisons were made with the development of chimpanzees in the same age range in a semi-natural zoo group (n = 25). We expected that young chimpanzees reared in a family group, which offers more variation in social partners than a pcer group, would show more frequent and diverse social behaviour; i.e. more social play, more triadic interactions (in play) and more sex differentiation in play, than young chimpanzees reared in peer groups. We were surprised to find that the peer group situation had little effect on social behaviour. The differences in the amount of gymnastics performed by peer groups and zoo groups can be interpreted as direct effects of the environmental conditions. The lower level of triadic play in the pccr groups may have been caused by the greater opportunity for diadic play; this effect was found only in young infants. The lower level of social play in individuals aged from three to six years in the peer groups was due to the presence of one group of carly-separated females and, hence, was not an overall and long-term effect of peer group rearing conditions. The absence of a sex difference in the amount of adolescent social play in peer groups and the presence of such a sex difference in the zoo shows that the social rearing condition has indeed some effect on the development of social behaviour. The fact that separation age and peer-only rearing conditions had no more marked effects on the development of social behaviour, obviously docs not imply that separating young infants from their mother is to be recommended, for many of the possible effects of separation and peer group rearing were not studied. However, since both the number of animals studied and the number of observation periods were large, the existence of only one difference is meaningful: young chimpanzees reared in an all family group show only slightly more diversity in the development of social behaviours than do young chimpanzccs reared in peer groups.

Early sensorimotor development in chimpanzees (Pan troglodytes).

The cognitive and locomotor development of 4 chimpanzees (Pan troglodytes) during their 1st year of life was examined with Piagetian theory and method as paradigm. The infant chimpanzees progressed through the same 4 stages of development as babies do. However, the chimpanzees seemed less developed than babies in object exploration and in object-object combination. When chimpanzee early cognition is compared with that of other nonhuman primates, chimpanzees appear more advanced than gorillas, capuchins, and macaques in these same areas of cognition and similar to orangutans. A unitary explantation of the relative advances and delays in chimpanzee early cognition, which refers to the relation between rates of locomotor and cognitive development, is proposed.

Early sensorimotor development in chimpanzees (Pan troglodytes).

Early sensorimotor development in chimpanzees (Pan troglodytes).

Behavioural Development in Chimpanzee (Pan troglodytes) and Human Newborns Across the First Month of Life

Comparisons among the behaviours of chimpanzee (Pan troglodytes) and human newborns on a standardised human neonatal assessment scale are reported for the infants at both 3 days and 1 month of age. Human infants scored significantly higher on the orientation cluster at both ages, and relative to the chimpanzee infants were lower in motoric maturity. With respect to the human standards employed, the two chimpanzee infants who were human-reared scored as optimally as did the human infants at 1 month, suggesting a differential impact of the care-giving environment on developing chimpanzee social behaviours.

Cognitive development in chimpanzee infants ( Pan troglodytes)

The present investigation sought to describe cognitive development in infant chimpanzees. To this end, two infant chimpanzees (Pan troglodytes) were assessed at four-week intervals, beginning at three months and continuing throughout the first year. Using materials suggested by Uzgiris and Hunt, the male and female infants were tested on, object permanence, means-ends relations, operational causality, and object relations. By way of a profile analysis, the sensorimotor abilities of the chimpanzee infants were compared to each other, and bore a striking similarity to published findings on human infants. Furthermore, as the early experiences of the chimpanzee more closcly approximated those of the human infant, the similarities became more apparent.

Observations on growth and development of chimpanzees

Observations on growth and development of chimpanzees