Tympanic Temperature Asymmetry and Stress Behavior in Rhesus Macaques and Children

OBJECTIVES: To examine left-to-right tympanic membrane temperature asymmetries and their possible association with biobehavioral stress responses in rhesus macaques and children. SUBJECTS AND DESIGN: Infrared tympanic membrane thermometry was completed bilaterally in 19 two-year-old rhesus macaques and 18 eight-year-old children in a cross-sectional, laboratory-based study. Unidirectional temperature gradients were calculated as the mean of two left-sided measurements minus the mean of two right-sided measurements. Biobehavioral stress responses were assessed in monkeys as agitated motor activity and adrenocortical activation after separation from the social group, and in children as parent-reported resilience to psychological stress and child behavior problems. RESULTS: Significant asymmetry was detected in tympanic membrane temperatures in both monkey and child samples, with left-sided temperatures measuring slightly but significantly higher than those from the right tympanic membrane. Higher-magnitude left-to-right temperature gradients were associated with stress-related locomotion in macaques and with lower resilience and more behavior problems in children. CONCLUSIONS: There are small but reliable asymmetries in the tympanic membrane temperatures of young human and nonhuman primates. Tympanic membrane temperature gradients reflect important individual differences in biologically derived responses to psychological stressors.