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The growth of mental attentional capacity in infancy: Evaluating the genetic contribution
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THE GROWTH OF MENTAL ATTENTIONAL CAPACITY IN INFANCY: EVALUATING THE GENETIC CONTRIBUTION Raymond H. Baillargeon, Richard E. Tremblay, and Daniel Perusse Axe de psychiatric preventive chez l’enfant et les jeunes Femand-Seguin Research Centre, 733 1 Hochelaga, Montreal, QC, Canada HlN 3V2 The growth of mental attentional capacity is proposed to account for the age related increase in the size of working memory. Mental-attentional capacity is operationally defined as the number of schemes that one can activate simultaneously in order to further his or her goal oriented activity. The amount of mental attentional capacity available in infancy (i.e., represented by the parameter e) is hypothesized to growth by one unit for each of the six Piagetian sensorimotor stages (such that p = 0, 1, 2, 3,4 and 5 for stages 1 to 6. respectively) (Alp, 1988; Benson, 1989; Pascual-Leone & Johnson, 1991). Furthermore, the growth of mental attentional capacity is taken to be genetically preprogrammed @mud-Leone & Goodman, 1979). The goal of the present study is to evaluate the heredity contribution in the growth of mental attentional capacity. Method Subjects Subjects were 161 twin pairs (50 monozygotic and 111 dizygotic). Twins were 5 months (corrected gestational age) at the time of the first wave of the Longitudinal Quebec Newborn Twins Study. Instruments Mental-attentional capacity was measured using a modified version of the Imitation Sorting Task (Alp, 1994; Benson, 1989). At the first difficulty level, the child had to grasp a coloured ring put on a platform within their reach. In order to succeed a child had to coordinate two schemes: vision and prehension. Each child was administered 5 trials. Bach trial was rated by an independent judge 1,2. and 3 for failure, partial success and success, respectively. The twins’s zygosity was determined using Goldsmith’s( 1991) Zygosity Questionnaire for Young Twins. Results Using multi-group latent class analysis (Lazarsfeld & Henry, 1968) we have identified three exclusive and exhaustive categories of babies on the basis of their performance on the Imitation Sorting Task. Babies who belong to the first latent category tended to fail all trials. Babies who belong to the second latent category tended to obtain partial success on all trials. And, finally, babies who belong to the third latent category tended to succeed on all trials. Preliminary results suggest a potentially high heritability of the growth of mental-attentional capacity. In fact, monozygotic twins who have a twin brother or sister that belong to the third latent category (i.e., success) were about 10 times more likely to be able to coordinate vision and prehension than those who have a twin brother or sister who can not yet coordinate two schemes. This likelihood is, however, substantially smaller for dizygotic twins. In fact, dizygotic twins who have a twin brother or sister that belong to the third category (i.e., success) were only 3.4 times more likely to be able to coordinate vision and prehension (i.e., e greater or equal to 2) than those who have a twin brother or sister who can not coordinate two schemes. Implications of these results for the heritability of the growth of mental attentional capacity will be diSCUSSed.
THE GROWTH OF MENTAL ATTENTIONAL CAPACITY IN INFANCY: EVALUATING THE GENETIC CONTRIBUTION Raymond H. Baillargeon, Richard E. Tremblay, and Daniel Perusse Axe de psychiatric preventive chez l’enfant et les jeunes Femand-Seguin Research Centre, 733 1 Hochelaga, Montreal, QC, Canada HlN 3V2 The growth of mental attentional capacity is proposed to account for the age related increase in the size of working memory. Mental-attentional capacity is operationally defined as the number of schemes that one can activate simultaneously in order to further his or her goal oriented activity. The amount of mental attentional capacity available in infancy (i.e., represented by the parameter e) is hypothesized to growth by one unit for each of the six Piagetian sensorimotor stages (such that p = 0, 1, 2, 3,4 and 5 for stages 1 to 6. respectively) (Alp, 1988; Benson, 1989; Pascual-Leone & Johnson, 1991). Furthermore, the growth of mental attentional capacity is taken to be genetically preprogrammed @mud-Leone & Goodman, 1979). The goal of the present study is to evaluate the heredity contribution in the growth of mental attentional capacity. Method Subjects Subjects were 161 twin pairs (50 monozygotic and 111 dizygotic). Twins were 5 months (corrected gestational age) at the time of the first wave of the Longitudinal Quebec Newborn Twins Study. Instruments Mental-attentional capacity was measured using a modified version of the Imitation Sorting Task (Alp, 1994; Benson, 1989). At the first difficulty level, the child had to grasp a coloured ring put on a platform within their reach. In order to succeed a child had to coordinate two schemes: vision and prehension. Each child was administered 5 trials. Bach trial was rated by an independent judge 1,2. and 3 for failure, partial success and success, respectively. The twins’s zygosity was determined using Goldsmith’s( 1991) Zygosity Questionnaire for Young Twins. Results Using multi-group latent class analysis (Lazarsfeld & Henry, 1968) we have identified three exclusive and exhaustive categories of babies on the basis of their performance on the Imitation Sorting Task. Babies who belong to the first latent category tended to fail all trials. Babies who belong to the second latent category tended to obtain partial success on all trials. And, finally, babies who belong to the third latent category tended to succeed on all trials. Preliminary results suggest a potentially high heritability of the growth of mental-attentional capacity. In fact, monozygotic twins who have a twin brother or sister that belong to the third latent category (i.e., success) were about 10 times more likely to be able to coordinate vision and prehension than those who have a twin brother or sister who can not yet coordinate two schemes. This likelihood is, however, substantially smaller for dizygotic twins. In fact, dizygotic twins who have a twin brother or sister that belong to the third category (i.e., success) were only 3.4 times more likely to be able to coordinate vision and prehension (i.e., e greater or equal to 2) than those who have a twin brother or sister who can not coordinate two schemes. Implications of these results for the heritability of the growth of mental attentional capacity will be diSCUSSed.