Environmental stressors and stable individual differences in human beh
avior have both been implicated etiologically in injuries. Because str
ess-related injuries are difficult to study experimentally in humans,
the authors examined injury incidence in a troop of 21 male and 15 fem
ale free-ranging rhesus macaques (Macaca mulatta) before, during, and
after a 6-month group confinement. Individual differences in behaviora
l inhibition to novelty were assessed, using multiple, quantified obse
rvations of behavior by 3 independent raters during 3 previous years.
Incidence and severity of medically attended injuries were ascertained
from veterinary records over a 2-year study period. A 5-fold increase
in the incidence of injuries was documented during confinement stress
, and an interaction was found between the stressor and behavioral inh
ibition in the prediction of injury incidence. Highly inhibited animal
s had significantly higher injury rates during confinement, compared w
ith their uninhibited peers, but equal or lower rates in the low stres
s periods that preceded and followed confinement. Inhibited individual
s appeared to have been specifically targeted for violence during the
group stressor but were protected under normative, more predictable co
nditions.