How biology shapes the development of shyness within specific contexts: A longitudinal, cross-lagged investigation

Shyness is a temperamental trait that refers to fear and wariness in the face of social novelty and is known to have a biological basis. One proposed physiological correlate of shyness has been the change in respiratory sinus arrhythmia (RSA) from baseline to a stressor. However, past research linking shyness and RSA change has been mixed, which may be, in part, due to a failure to carefully consider the context under which RSA change is measured and the directionality of relations. Using a longitudinal design and cross-lagged analysis (N = 103, 52 girls), we examined parent-reported shyness and RSA change during a stranger approach task (social stressor) and a locked box task (nonsocial stressor) at ages 3 (M_age at Time 1 = 3.50 years, SD_age = 0.19 years) and 4 (M_age at Time 2 = 4.76 years, SD_age = 0.38). Cardiac vagal withdrawal during the stranger approach task, but not during the frustration task, at age 3 positively predicted shyness at age 4. Shyness at age 3 did not predict cardiac vagal change in either context at age 4. We also found that changes in RSA measured during the frustration task were stable across time, but changes in RSA measured during the stranger approach task were not stable across time, suggesting a developmental change in physiological regulatory systems to social threat. These results suggest that, although biology may come first in shaping children's behavior, this relation depends critically on the context and the incentives in the child's environment. (PsycInfo Database Record (c) 2024 APA, all rights reserved).