This study examined individual differences in the development of naming skills in ten children with Down syndrome. The production, comprehension, and imitation of object names, along with developmental ages (DA) were assessed every three months from 3 to 6 years of age. During elementary school, IQ was also tested. Four major profiles were identified : associated, dissociated, non-nominal, and severely delayed. DA at which children attained a 3-word level of comprehension showed a split into two groups. Mean DA was 21 months for early comprehenders, who attained this level by the age of 3. Whereas the DA of late comprehenders was above 36 months, and their comprehension skills developed more slowly than would be expected by their DA. In addition, late comprehenders showed a lower IQ score than early comprehenders during elementary school. The results suggest that comprehension skills are more strongly associated with intellectual functions than are rote production skills. Causal mechanisms underlying the four profiles appear to be related to developmental dissociations between comprehension and rote production skills.

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The present study concerned the role of tactile-kinesthetic experience in the emergence of the perception of causality. It investigated whether or not the manual operation of a moving target presented on a PC monitor would change young children's perception of a causal stimulus. After a practice session where participants (100 4- to 6-year old children) stopped a horizontally moving target by pressing one of the keys on a keyboard, the percentage of children who reported the causal relation between colliding objects was higher than that before the practice session. But repeated observations of causal stimuli by a different fourty-three 4- to 6-year old children did not reveal any changes in their perceptions of causal stimuli. These results indicated that young children's perceptions of causality is strongly related to tactile-kinesthetic experiences. The results are thought to show that the perceptual-motor workspace (Newell, 1986), restructured by manual operation of a moving target, made it easier for children to find invariant information as a causal stimulus.

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This study examined the inability of autistic children to comprehend backward pointing. Backward pointing refers to when an experimenter points in the direction behind a child's back. The comprehension of backward pointing was assessed as a precursor to language. To examine the joint attention function, the experimenter pointed at bubbles because the children showed interest in bubbles. Experiment I involved 53 infants (5 months to 1 year 8 months). Participants in Experiment II were 23 autistic children. The results demonstrated that autistic children with mental age of 13 months and above were as capable of comprehending pointing as were the infants. However unlike the infants, the autistic children could not produce intentional behaviors related to sharing. Deficits in establishing joint attention among the autistic children appeared to be related to the concept of others as intentional agents who possess independent psychological states such as interest in objects.

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The Novel Label Task (Callanan, 1989) was used to examine 3 situational factors as adults named objects and children interpreted the names. The 3 factors were (1) the number of target item, (2) the conceptual level of probe item, and (3) how the probe item was presented. Participants were 120 children, ages 4 to 5 years. When a target item was labeled with a novel word, children interpreted the label in reference to the lowest conceptual level of the probe item. They also interpreted names more easily when multiple probe items were presented together. Finally, when two target items were labeled with novel words, children tended to interpret them refering to the name at the conceptual level which included these items. These findings suggest that situations in which adults label new words and children interpret their labels play an important role in the acquisition of word meanings by young children.

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This research concerns developmental processes in the use of stone tools by wild chimpanzees in Bossou, Guinea. Previous studies had shown that chimpanzees in Bossou began at age 3.5 years to use a pair of stones as a hammer and anvil to crack open nuts. A field experiment was conducted to clarify developmental processes, at an outdoor laboratory where stones and oil-palm nuts were provided by the experimenter. We directly observed and video-recorded infant chimpanzees' object manipulation in a social context, which is a prerequisite for nut-cracking. This paper is based on data collected between 1992 and 1994 consisting of all episodes of behavior related to nut/stone manipulation and nut-cracking. Six infant chimpanzees under the age of 3 years were observed. A total of 310 behavioral episodes were grouped first into 5 major behavioral categories: (1) manipulation of nuts, (2) manipulation of stones, (3) manipulation of both nuts and stones, (4) manipulation of nuts and/or stones while interacting with the other individuals, and (5) interaction with the other individuals who perform nut-cracking. Each of these categories was subdivided into 2-4 subcategories by looking at qualitative differences in behavior, such as direction of manipulation, plurality of manipulated objects, and temporal sequence. Relative frequencies of behavioral episodes for each category or subcategory was compared among three age groups: 0.5, 1.5, and 2.5 year olds. The development of manipulation skills may be characterized as follows. Infants increased in the number of behaviors in which they manipulated both nuts and stones successively and/or simultaneously, while interacting with the other individuals. These other individuals may play an important role as a safe-base for exploration of nut/stone manipulation, and as a model for emulation learning.

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The present study analyzed the effects of different settings and maternal styles on mothers' and children's references to internal states. Fifty-one 2- and 3- year olds and their mothers were observed in three settings at home : pretend play, reading, and eating. Interview and questionnaire data were collected to assess individual differences in maternal styles. Mothers' references to internal states differed significantly according to the setting. For the pretend play setting, mothers mentioned feeling states more frequently than for other situations. In the reading setting, both mothers and children talked about mental states more often than in other situations. And in the eating situation, mothers used terms related to desires more than in other settings. In addition, individual differences in mothers' references to internal states during interviews were associated with their references to internal states during their interactions with children, and to children's references to internal states. These findings suggest that both (1) the types of settings in which mothers are experienced in daily contacts with children and (2) characteristics of mothers have important influences on the development of children's understanding of internal states.

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Correlations between environmental measure and children's behavior have traditionally been interpreted by developmental psychologists as "environmental effects". The purpose of this paper was to report a critical replication of Akita's (1992) study on the influence of family environment on children's reading activities, from the point of view of behavioral genetics. Thirty pairs of identical twins, 20 pairs of fraternal twins (6th graders) and their parents completed questionnaires about their families' reading environment. The children also evaluated their own involvement in reading activities. Aspects of the family environment, as perceived by parents, were moderately correlated with perceptions by children. Children's perceptions of direct parent-child interaction, such as facilitation of reading, indicated genetic influences. However, twins' preferences for reading were affected by the quantity of books perceived by the parents, and not by genetic factors.

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The processes by which a human acquired the ability to perceive visual form were investigated in a congenitally blind subject who gained sight through an operation performed at the age of 12. After the operation, she could identify motion, color, and 2-dimensional direction, and could also discriminate 2-dimensional size, but not forms (e.g., triangle, square, circle). The results may be summarized as follows : (1) When attempting to see the form on a board, the subject moved her head and for a board in her hands. (2) In her visual processes of identifying the form, she comparedsizes and/or directions of the form picked up by her head movement and/or the board movement with her internal knowledge, wherein the visual form image consisted of verbalized information about the sizes and/or directions of the form. On the other hand, the tactual form image consisted of the whole of the figure. (3) The reaction time was shortened, when the situation was changed from identification to discrimination.

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