Untitled

Stress Effects on the Developing Brain 135ence of the responsive caregiver somehow blocks activation of the HPA axis (seealso Spangler & Schieche, 1998). This is true even for babies who are expressinghigh distress—that is, even when the emotion component of the stress-emotion systemappears to be activated by the stressor. In contrast, if the infant is with someonewho is insensitive, unresponsive, or intrusive, that person’s presence does not blockactivation of the HPA axis and significant correlations between behavioral distressand cortisol elevations are observed.Much of this information comes from laboratory experiments and thus may bedifficult to generalize to life as it unfolds outside the laboratory. However, tworecent studies suggest that this laboratory research has captured real-world phenomena.The first study examined children in Berlin, Germany, who were enteringchild care for the first time as toddlers (Ahnert, Gunnar, Lamb, & Barthel,2004). In Berlin, women typically stay at home with the infant for the first year,and then return to work in the baby’s second year. Furthermore, the child-carecenters encourage mothers to spend a number of days adapting their toddlers tothe child-care setting before the first real child-care day.A month before the children started child care, Ahnert and colleagues (2004)assessed the security of the infant-mother attachment relationship using the StrangeSituation assessment and collected salivary cortisol levels at home in the morningat about the same time of day as the children would soon be leaving the house forchild care. They then collected salivary cortisol levels at child care during the adaptationperiod when the mothers accompanied the children and over the first weekswhen the child attended child care in the mother’s absence. Finally, samples weretaken at child care after 5 months of child-care attendance. As shown in figure 6-3,infants in insecure mother-toddler attachment relationships exhibited significantelevations in cortisol during the adaptation period (left side of graph). We can speculateonly that the child-care setting with new adults, new children, and excitingopportunities for exploration was a potent novelty-stressor for the toddlers, thusactivating the HPA axis. Nonetheless, toddlers in secure attachment relationshipsdid not exhibit the same cortisol elevations. The presence of the mother in a securerelationship appeared to be the critical factor, because when the mother was notpresent (see first separation day), her toddler’s cortisol levels soared to levels previouslyshown by only the toddlers in insecure attachment relationships.The second study underscores the fact that it may be the quality of nurturanceor care the child receives, and not whether that care is provided by the mother orfather for that matter. In this study, preschoolers in family-based child care providedcortisol sample at midmorning and midafternoon. Our research group hadpreviously shown that cortisol levels tend to rise over the day at child care andthat these increases are the most marked among toddlers (Dettling, Gunnar, &Donzella, 1999). In addition to measuring cortisol, Dettling and colleagues(Dettling, Parker, Lane, Sebanc, & Gunnar, 2000) also observed care provider–child interactions using the instrument developed by the NICHD child care study