Biomedical subjects

Masako Myowa-Yamakoshi

Publications and source records attributed to Masako Myowa-Yamakoshi.

5 recordsLinked to original sources

PubMed2005

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.

Agonistic Behavior↗

PubMed2004

Contagious yawning in chimpanzees.

Six adult female chimpanzees were shown video scenes of chimpanzees repeatedly yawning or of chimpanzees showing open-mouth facial expressions that were not yawns. Two out of the six females showed significantly higher frequencies of yawning in response to yawn videos; no chimpanzees showed the inverse. Three infant chimpanzees that accompanied their mothers did not yawn at all. These data are highly reminiscent of the contagious yawning effects reported for humans. Contagious yawning is thought to be based on the capacity for empathy. Contagious yawning in chimpanzees provides further evidence that these apes may possess advanced self-awareness and empathic abilities.

Animals↗

PubMed2004

Imitation in neonatal chimpanzees (Pan troglodytes).

This paper provides evidence for imitative abilities in neonatal chimpanzees (Pan troglodytes), our closest relatives. Two chimpanzees were reared from birth by their biological mothers. At less than 7 days of age the chimpanzees could discriminate between, and imitate, human facial gestures (tongue protrusion and mouth opening). By the time they were 2 months old, however, the chimpanzees no longer imitated the gestures. They began to perform mouth opening frequently in response to any of the three facial gestures presented to them. These findings suggest that neonatal facial imitation is most likely an innate ability, developed through natural selection in humans and in chimpanzees. The relationship between the disappearance of neonatal imitation and the development of social communicative behavior is discussed from an evolutionary perspective.

Age Factors↗

PubMed2003

New observations of ant-dipping techniques in wild chimpanzees at Bossou, Guinea.

Ant-dipping behavior is often cited as a clear example of chimpanzee culture, since different populations have apparently different dipping techniques (the one-handed method used by chimpanzees in Bossou, Guinea and Taï, Côte d'Ivoire, and the two-handed method used in Gombe, Tanzania). Here we report a new observation of ant-dipping behavior from Bossou using the two-handed method, in addition to the first detailed description of the one-handed method. Although the main dipping pattern was the one-handed method in Bossou, one adult male was observed dipping for ants using the two-handed method, while other chimpanzees employed the conventional one-handed method in the same episode. The two-handed method was also sporadically observed in a juvenile and in adolescents, who were still immature in dipping techniques and hence prone to suffer from ant attacks. Cross-population comparisons of dipping techniques suggest that there are two sub-types of the one-handed method, and the Bossou one-handed technique may be substantially different from that of Taï. In terms of overall behavioral repertoire in ant dipping, the Bossou pattern appears more similar to that of Gombe than Taï. This may be explained by the difference in target ant species.

Age Factors↗

PubMed2003

Preference for human direct gaze in infant chimpanzees (Pan troglodytes).

We studied gaze perception in three infant chimpanzees (Pan troglodytes), aged 10-32 weeks, using a two-choice preferential-looking paradigm. The infants were presented with two photographs of a human face: (a) with the eyes open or closed, and (b) with a direct or an averted gaze. We found that the chimpanzees preferred looking at the direct-gaze face. However, in the context of scrambled faces, the infants showed no difference in gaze discrimination between direct and averted gazes. These findings suggest that gaze perception by chimpanzees may be influenced by the surrounding facial context. The relationship between gaze perception, face processing, and the adaptive significance of gaze perception are discussed from an evolutionary perspective.

Animals↗