Yasuhiro Shizawa

Osaka University, Suika, Ōsaka, Japan

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Publications (7)7.27 Total impact

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    ABSTRACT: Children's cooperative activities with their peers become markedly coordinated during the 3rd year of life. During these activities, the child needs to follow his/her peers' gaze to objects, and look at the same objects to initiate coordinated action. Since 3-year-olds' ability to follow their peers' gaze has not been studied, we experimentally investigated this in our study. In the experimental trials, an experimenter induced a child (looker) to look at a doll on display, and observed the reaction of another child (follower) who was in front of the looker (and not looking at the doll). In the control trials, the experimenter displayed the doll in an identical manner when the follower was alone. The followers followed the gaze of the lookers, looking at the doll in approximately 90% of the experimental trials, compared with 20% of the control trials. These results indicate that 3-year-olds can follow their peers' gaze.
    Infant behavior & development 05/2008; 31(2):280-6. · 1.34 Impact Factor
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    ABSTRACT: In the field of developmental psychology, there is speculation that pointing gestures by infants are good precursors of infant language acquisition, and some researchers have found correlations between these pointing gestures and some indices of language acquisition. Infants' pointing gestures are presumably related to language acquisition because they provoke verbal responses from adults. To test this, seven boys and six girls were observed during free play time in a nursery classroom, and post-pointing and matched-control data were collected. Comparison between these data confirmed that the nursery staff spoke to infants at a significantly earlier stage in post-pointing sequences, compared with control sequences, indicating that pointing gestures elicit verbal responses from adult caregivers.
    Infant behavior & development 01/2008; 30(4):562-7. · 1.34 Impact Factor
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    ABSTRACT: This study examined whether the choice of interactors is influenced by indoor and outdoor situations. Peer relations among twenty three-year-old, eighteen four-year-old, and twenty five-year-old children in an urban preschool in Japan were observed during indoor and outdoor free play situations. We analyzed the partners in the interactions, the number, and the stability of interactors. The Shannon-Wiener diversity index (H) was used to measure the stability of interactors. In outdoor situations, three-year-old and four-year-old children were involved with a diversity of interactors, while four-year-old children's preferred friends were stable. Five-year-old children showed a relation with stable interactors in both indoor and outdoor situations, choosing different interactors in each situation. In addition, the children who had few interactors in indoor situations increased their relations with interactors in outdoor situations. These results suggest that three-year-old and four-year-old children are affected by environmental factors that seem to stimulate the children's physiognomic perception, whereas five-year-old children make use of the environment. Opportunities for children to encounter various situations and meet various peers may facilitate the development of social relations.
    Shinrigaku kenkyu: The Japanese journal of psychology 05/2006; 77(1):40-7.
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    ABSTRACT: The present study examined grooming relationships of adolescent females in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama. To assess whether the loss of the mother influenced the grooming relationships of adolescent females (5-7 years old), we compared the time spent in grooming interactions and the number of grooming partners among the following three groups: 6 adolescent orphans with sisters, 9 adolescent orphans without sisters, and 11 adolescent non-orphans with surviving mothers. In Japanese macaques, grooming most frequently occurs between mothers and their daughters. Therefore, it is expected that if the mother is lost, orphans will devote less time to grooming interactions than non-orphans. However, the time spent in overall grooming interactions did not differ among the three groups. While non-orphans maintained grooming relationships with their mothers, orphans acquired alternative grooming relationships with other group members. Orphans adopted two kinds of tactics to compensate for the loss of the mother. First, adolescent orphans with sisters developed more affiliative grooming relationships with their sisters than non-orphans with sisters. Secondly, adolescent orphans without sisters spent more time in grooming interactions with same-aged females and non-related adult females. Moreover, regarding grooming interactions with same-aged females and non-related adult females, orphans without sisters had a larger number of grooming partners than non-orphans. These results indicate that adolescent females have enough flexibility to develop their grooming network after the loss of their mothers, and that the lack of mother and sisters might accelerate socialization of adolescent females and enable them to be integrated in reciprocal adult grooming relationships.
    Primates 05/2005; 46(2):145-50. · 1.29 Impact Factor
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    ABSTRACT: Calls emitted by infants when the infant loses sight of its parents are useful to estimate the infant's requirement for parental care. When an Old World monkey infant loses sight of its mother it emits whistles. Therefore, it would be interesting to determine whether mothers could distinguish their own infant's whistles from the whistles of other infants. The response of each of seven Japanese macaque (Macaca fuscata) mothers to her own infant's whistle was compared with their responses to another infant's whistle. Matched control playback experiments were performed when the infants were four to six months old. The results showed that each mother could distinguish her own infant's whistle from that of another infant when the infants were four to six months old. Although a stricter experimental plan is required to further examine the issue, we found that the dominance rank of the infant's mother was another important factor in the female response to the infant's call. The finding suggests that females can associate a call emitted by an infant with its mother's rank, even before the infant begins to wander far from its mother.
    Behavioural Processes 02/2005; 68(1):41-6. · 1.51 Impact Factor
  • Primate Research 01/2004; 20(1):31-43.
  • Masayuki Nakamichi, Yasuhiro Shizawa
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    ABSTRACT: We analyzed grooming episodes recorded among adult females in a large, provisioned, free-ranging group of Japanese macaques (Macaca fuscata) at an individual level. Each female groomed on average 10 of the other 84 females, and 54% of them devoted 50% of their grooming to a single female grooming partner, which indicates that most females had grooming interactions with a relatively small subset of available females. Although 65% of the total grooming bouts were between related females, 25% of females disproportionately groomed unrelated females, 22% groomed related and unrelated females equally, and grooming was kin-biased for the remaining 53%. Moreover, 11 of 16 kin-groups included at least one female that groomed unrelated females significantly more often than related females. In 18% of unrelated dyads, grooming was directed down the hierarchy, in 58%, grooming was well-balanced between the two females, and in the remaining 25%, grooming was directed up the hierarchy. The results indicate that although Japanese macaques are considered a despotic species based on their dominance style, this group included some females that showed egalitarian tendencies, i.e., grooming was directed down the hierarchy or was well-balanced, and was directed toward unrelated females as often as or more often than toward related females. The presence of egalitarian individuals might be important to maintain a well-organized, female-bonded group.
    International Journal of Primatology 05/2003; 24(3):607-625. · 1.79 Impact Factor