In two studies comprising 249 children and their families, the authors
utilized secondary, exploratory data analyses to examine Boyce and
Ellis' (this issue) evolutionary–developmental theory of
biological sensitivity to context. The theory proposes that individual
differences in stress reactivity constitute variation in susceptibility to
environmental influence, both positive and negative, and that early
childhood exposures to either highly protective or acutely stressful
environments result in heightened reactivity. In Study 1, 127 3- to 5-year
old children were concurrently assessed on levels of support/adversity
in home and preschool environments and on cardiovascular reactivity to
laboratory challenges. In Study 2, 122 children were prospectively
assessed on familial stress in both infancy and preschool and on autonomic
and adrenocortical reactivity to laboratory challenges at age 7. In both
studies, a disproportionate number of children in supportive, low stress
environments displayed high autonomic reactivity. Conversely, in Study 2,
a relatively high proportion of children in very stressful environments
showed evidence of heightened sympathetic and adrenocortical reactivity.
Consistent with the evolutionary–developmental theory, the
exploratory analyses also generated the testable hypothesis that relations
between levels of childhood support/adversity and the magnitude of
stress reactivity are curvilinear, with children from moderately stressful
environments displaying the lowest reactivity levels in both studies.The research on which this paper was based was
supported by grants from the John D. and Catherine T. MacArthur
Foundation's Research Network on Psychopathology and Development, the
National Institute of Child Health and Human Development (1RO1 HD 24718),
and the National Institute of Mental Health (R01-MH44340 and P50-MH53524).
We thank Jay Belsky and David Bjorklund for comments on an earlier draft
of this paper.