Birth Order and Physiological Stress Response

Studies of the relation between birth order and anxiety have reported inconsistent results. However the measures of anxiety employed have often been either subjective or indirect. The purpose of the present study was to assess the relation between birth order and anxiety using direct and objective measures. Heart and respiration rates of 14 first- and 15 later-born white male adolescents were obtained under 1 resting and 4 stress conditions (Tone Shock Problems and Problems plus Criticism). Respiration rates were not different for the 2 groups but firstborns heart rates were elevated under all including the resting conditions. When resting heart rates were matched for 8 pairs of first- and later borns firstborns heart rates were still elevated under the stress conditions. Implications of these findings for birth-order theory and for further research are discussed as are certain restrictions on the generalization of the findings. (authors)