This thesis addressed the physiological impact of fear in 4- and 7-year-old children, induced by media and social fear-inducing tasks (the Trier Social Stress Test for Children). The main question pertained to individual differences in physiological reactivity to fear-inducing stimuli. The possibly relevant factors of attachment security, the child’s temperamental fearfulness, and variations in the serotonin transporter gene (5-HTTLPR; long vs. short allele) were taken into account. Results showed that temperament, attachment, and genetic influences play significant and interactive roles in the expression of fear reactivity. A secure relationship affected the reactivity to media-induced fear stimuli in temperamentally more fearful children but not in less fearful children irrespective of children’s ages. This finding adds to the growing literature showing that children high in negative emotion are more susceptible to positive as well as negative rearing influences. Furthermore, we found evidence that reactivity to the social fear-inducing task was explained by a combination of variations in the serotonin transporter gene and attachment security. Children with a secure attachment representation and two long 5-HTT alleles showed the lowest levels of fear reactivity, indicating that physiological reactivity to a social fear-inducing task is a product of the child’s biology and environment.
