Differences between Japanese Infants and Caucasian American Infants in Behavioral and Cortisol Response to Inoculation

The behavioral and cortisol responses of Japanese infants and Caucasian American infants, 4 months of age, were observed during and following routine inoculation. The Caucasian American group showed a more intense initial affective response and a longer latency to quiet than the Japanese group; the Japanese group showed a greater cortisol response. A 4-group taxonomy was created based on high or low behavioral and cortisol response: high behavior–high cortisol, low behavior–low cortisol, high behavior–low cortisol, and low behavior–high cortisol. There were significant differences between the 2 groups of infants using this taxonomy: Infants in the Caucasian American group were more likely to fall in the high behavior–low cortisol group, while infants in the Japanese group were more likely to fall in the low behavior–high cortisol group.