Young children’s cortisol responses showed consistent differences across cultures and situations, suggesting that biological adaptations to culture may occur early in development. With cultural emphases on self-improvement and achievement from an early age (Chao & Tseng, 2002; Stevenson et al., 1990), an achievement-related stressor elicited an increased cortisol response among Chinese preschoolers, suggesting that they may have already internalized achievement failure as a salient threat to their representation of self (Ng et al., 2007). Given the cultural emphasis on social connections among Japanese preschoolers, the stressor related to interpersonal harmony elicited an increased cortisol response. This finding is consistent with research on the importance of interdependent self-constructs in Japanese adults (Markus & Kitayama, 1991), suggesting that Japanese children may have already internalized this value. We also found some evidence that Japanese children may react to achievement-related stressors (relative to baseline), although this result was not significant when compared with those of the control task. Collectively, it remains possible that achievement-related stressors may evoke a stronger reactivity of the HPA axis among Chinese and Japanese preschoolers relative to U.S. preschoolers. Nevertheless, children’s biological responsivity to culturally relevant stressors suggests that culture is deeply embedded in biological systems and that it influences neuroendocrine responses and furthers our potential for cultural learning.
U.S. preschoolers showed a decreased level of cortisol across both achievement-related and interpersonal-relationship- related stressors relative to baseline, which is consistent with the findings of some prior studies showing decreased cortisol following exposure to a laboratory stressor in young children (e.g., Dougherty et al., 2011). However, U.S. children were more reactive than others to anticipatory stress during the acclimation period, which may have inflated the baseline cortisol level given that elevated cortisol levels may require a prolonged period for recovery (Liu et al., 2017). Consistent with our findings, results from a study by Lopez- Duran et al. (2009), who controlled for participants’ cortisol levels on their arrival to the lab, showed that typically developing American children showed a decrease from 30 min prior to the stressor and did not show changes in cortisol from 0 to 60 min after fear- or frustration-based stressors. Indeed, U.S. children showed higher cortisol levels when samples were collected in a novel laboratory setting, relative to the home environment (Gunnar & Talge, 2008), and an increased cortisol response in the laboratory only when the stress paradigm was administered with an unfamiliar and unfriendly experimenter (Roos et al., 2017). They also exhibited increased levels of cortisol in day-care settings that were positively correlated with their anxiety levels (Gunnar et al., 2010). It is possible that U.S. preschoolers in moderate-sized communities may react to novelty and anticipatory stress to a greater extent than Chinese (Beijing) and Japanese (western suburbs of Tokyo) children who live in much denser environments and may be more used to seeing and interacting with people outside their immediate family or preschool settings. Alternatively, an impending period of separation from one’s caregiver may in fact be a culturally relevant stressor to the U.S. preschoolers, and, to some extent, to the Japanese preschoolers in our sample.
Notably, we found that Chinese preschoolers had higher overall cortisol levels than U.S. and Japanese preschoolers (Fig. 1). It is possible that the higher cortisol levels among Chinese preschoolers might have been influenced not by cultural factors per se but by the quality and number of children in the day-care environment, longer or more crowded commuting experiences, or other factors related to population density and rapid urbanization that are not systematically measured in our study. Nevertheless, our findings are consistent with accumulating research demonstrating that East Asian infants (e.g., Chinese American) are less behaviorally reactive but showed higher cortisol responses than Caucasian American infants to a variety of stressors (Friedlmeier et al., 2015; Kagan & Fox, 2006). Cross-cultural research suggests that North American children expressed more negative emotions than Asian children (e.g., Ip et al., 2021; Lewis et al., 2010). These cross-cultural differences may be related in part to differences in parental socialization of emotional expression (Raval & Walker, 2019). 
Several caveats and future considerations apply. First, small sample sizes render our conclusions preliminary. Future research with larger samples is needed to examine individual differences in cortisol reactivity among children within each culture. Second, our sample was mostly middle class and was recruited from relatively urban areas with predominantly mainstream majority families. Findings may not generalize to children from other sociodemographic backgrounds or to those living in other areas within these countries. Third, although our findings suggest that cultural contexts may influence cortisol responsivity, our study did not directly assess cultural values in these families. Fourth, following prior studies conducted in North America (Kryski et al., 2011; Tolep & Dougherty, 2014), we included a 30-min acclimation period. However, our empirical data suggest that a longer (i.e., 60-min) acclimation period would be more ideal for capturing a true baseline for acute stress responses and for eliminating cortisol reactivity during this period.
Finally, it is difficult to disentangle social fear and disappointment in our gift paradigm, so this issue requires further investigation. Replications and longitudinal follow-up studies with multiple levels of analysis (e.g., self-report, heart rate) are needed to further examine the reliability and validity of these tasks as well as to demonstrate cultural validity (Olson et al., 2019). It would be invalid to repeat the same tasks for children within a sample because the tasks involve an unexpected outcome that would be predictable if repeated. Nonetheless, our findings highlight the importance of understanding the psychological underpinnings of psychosocial stressors that elicit heightened neuroendocrine responses in young children.
