- Email: [email protected]
stranger anxiety
295
BEHAVIOR
GENETIC DIFFERENCES IN THE ONSET OF CRAWLING/ AND SEPARATION/ STRANGER ANXIETY
WALKING
N. AKSAN, J. BHIUN, K. BUSS, K. LEMERY, H. H. GOLDSMITH [email protected] Behavior genetic studies allow developmentalists the unique opportunity to examine genetic and environmental underpinnings of various milestones from emotional to physical development. Our goal is to examine their relative influence on the timing of various milestones such as separation, stranger anxiety as well as crawling and walking. Most behavior genetic studies have examined the relative contribution of genetic and environmental influences in the extent to which a certain trait expressed. For example, individual differences in temperament dimensions and physical growth rates have been shown. Earlier studies using small samples have also suggested that there may be genetic underpinnings in the onset of various milestones such as tooth eruption and social smiling. Thus, the researchers have focused on the heritability of the level of trait expression rather than the timing and onset of milestones. It is also the case that genetically based differences are often established for a limited set of variables that are typically associated with specific domains of study, such as physical or motoric development. Using twin data the recently launched Wisconsin Twin Project &emery dz Goldsmith, 1995) we examined the genetic underpinnings of onsets of developmental milestones from multiple domains. For instance, in the socioemotional domain, we examined milestones such as, separation and stranger anxiety, and in the motoric domain milestones such as, crawling and walking. We used phone interview data from 114 mothers of twins (n=70 for monozygotic, MZ, and N=54 for dizygotic, DZ, pairs). Mothers were asked to rate the difference, in days (O-180 days), for the onset of various milestones. We examined mean differences in the onset of crawling, walking, separation and stranger anxiety using two sample t-tests for MZ and DZ twins. These tests revealed a difference of 12 days in the onset of crawling for MZ twins and a difference of 27 days for DZ twins to be significantly different, p < .Ol. Similarly, a 12 days difference for MZ and a 38 day difference for DZ twins in the onset of walking was also significant, g < .Ol. We also found greater similarity between MZ twins in the onset of separation anxiety, 9 days, than for fraternal twins, 24 days, p < .05. No such significant differences were found for the onset of stranger anxiety, however there was a significant reduction in the sample size for this latter test. To this pool of milestones we will be adding differences in the onset of first tooth eruption, and one, two and three word sentence use. The results suggest that relevant developmental phenomena are overlooked when behavior geneticists limit their analyses to levels of trait expression.
BEHAVIOR
GENETIC DIFFERENCES IN THE ONSET OF CRAWLING/ AND SEPARATION/ STRANGER ANXIETY
WALKING
N. AKSAN, J. BHIUN, K. BUSS, K. LEMERY, H. H. GOLDSMITH [email protected] Behavior genetic studies allow developmentalists the unique opportunity to examine genetic and environmental underpinnings of various milestones from emotional to physical development. Our goal is to examine their relative influence on the timing of various milestones such as separation, stranger anxiety as well as crawling and walking. Most behavior genetic studies have examined the relative contribution of genetic and environmental influences in the extent to which a certain trait expressed. For example, individual differences in temperament dimensions and physical growth rates have been shown. Earlier studies using small samples have also suggested that there may be genetic underpinnings in the onset of various milestones such as tooth eruption and social smiling. Thus, the researchers have focused on the heritability of the level of trait expression rather than the timing and onset of milestones. It is also the case that genetically based differences are often established for a limited set of variables that are typically associated with specific domains of study, such as physical or motoric development. Using twin data the recently launched Wisconsin Twin Project &emery dz Goldsmith, 1995) we examined the genetic underpinnings of onsets of developmental milestones from multiple domains. For instance, in the socioemotional domain, we examined milestones such as, separation and stranger anxiety, and in the motoric domain milestones such as, crawling and walking. We used phone interview data from 114 mothers of twins (n=70 for monozygotic, MZ, and N=54 for dizygotic, DZ, pairs). Mothers were asked to rate the difference, in days (O-180 days), for the onset of various milestones. We examined mean differences in the onset of crawling, walking, separation and stranger anxiety using two sample t-tests for MZ and DZ twins. These tests revealed a difference of 12 days in the onset of crawling for MZ twins and a difference of 27 days for DZ twins to be significantly different, p < .Ol. Similarly, a 12 days difference for MZ and a 38 day difference for DZ twins in the onset of walking was also significant, g < .Ol. We also found greater similarity between MZ twins in the onset of separation anxiety, 9 days, than for fraternal twins, 24 days, p < .05. No such significant differences were found for the onset of stranger anxiety, however there was a significant reduction in the sample size for this latter test. To this pool of milestones we will be adding differences in the onset of first tooth eruption, and one, two and three word sentence use. The results suggest that relevant developmental phenomena are overlooked when behavior geneticists limit their analyses to levels of trait expression.