Activity level in the lab: Overlap with shyness indicates it is more than pure motoric activity

Authors: FRAZIER-WOOD, ALEXIS - Children'S Nutrition Research Center (CNRC); SAUDINO, KIMBERLY - Boston University

Submitted to: Developmental Psychology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2017
Publication Date: 6/29/2017
Citation: Frazier-Wood, A.C., Saudino, K.J. 2017. Activity level in the lab: Overlap with shyness indicates it is more than pure motoric activity. Developmental Psychology. doi:10.1037/dev0000348.

Interpretive Summary: Children's activity level is different when they are put in a new environment, compared to environments with which they are familiar. What influences the extent to which a child changes their activity level across such environments is not understood. We examined activity level data, measured by actigraphs which are a mechanical assessment of activity level, from over 600 young children in 2 situations: a familiar environment (the home) and an unfamiliar environment (the lab). We did this when the children were two and three years of age, and found that almost half of the difference in activity level between the home and the lab could be attributed to shyness – whether shyness was assessed by the parent via a questionnaire, or by trained study staff via observation. This finding was also found whether we used genetic information over half of the difference in activity level between the two environments could be attributable to genes shared with shyness. These findings were also consistent at both ages (two and three years). These results suggest that a child's activity level in a new situation is reflective of other aspects of their temperament, such as their shyness, and this information will be useful for researchers who want to think up ways to increase a child's activity level in novel situations. Such efforts to increase activity level may help prevent weight gain in this group.

Technical Abstract: The observation that children's activity level (AL) differs between novel and familiar situations is well established. What influences individual differences in how AL is different across these situations is less well understood. Drawing on animal literature, which links rats' AL when 1st placed in a novel setting with novelty seeking phenotypes, and child temperament literature, which links AL, novelty response, and shyness, we hypothesized that shyness would be an important component of children's AL in a novel situation. We examined this using mechanically assessed AL from 2 situations (the home and the lab) and 2 measures of shyness (1 parent-rated and 1 observer-rated) on up to 313 twin pairs (145 monozygotic and 168 dizygotic), at 2 and 3 years of age. Biometric genetic models removed from lab AL the variance shared with home AL, representing what was different in AL when the child entered the lab compared to the home. We report that almost half (43%) of the genetic component of AL in the lab was independent of AL in the home, and this unique genetic component shared genetic covariance with shyness. Shyness influences AL in a novel situation such as the lab, indicating that mechanically assessed AL represents more than global motoric activity and provides information on a child's temperamental response to novelty.