VII. GENERAL DISCUSSION

Themain goal of the present study was to attain a better understanding of individual and age differences in infants’ neuroendocrine stress responses in association with the ability to acquire and remember information. We conducted a longitudinal study that included five laboratory visits at 3, 6, 8, 10, and 12 months of age during which infants were tested with a series of cognitive tasks. At each visit, salivary cortisol levels were obtained for both infants and their mother at two times: pretask (T1) and posttask (T2). We investigated whether, in the context of our learning event paradigm, a decreasing cortisol response pattern is associated with greater maturity, and whether or not this phenomenon interacted with constitutional (gender) or social (maternal sensitivity) factors. We investigated five main topics: (a) whether specific infant cortisol response patterns are associated with better and worse cognitive performance during a learning event; (b) whether greater maternal sensitivity is associated with better cognitive performance in infancy; (c) the association between infant cortisol measures and maternal sensitivity; (d) associations between infant and maternal cortisol measures, and with maternal sensitivity, across the first year as potential support for the claim of an external to internal shift in the regulation of infant neuroendocrine response; and (e) the degree of stability and change in cortisol response patterns during the first year of life. It is no secret that infant studies are very difficult to conduct, in part, because the population under study, although human to be sure, is extremely cognitively immature and cannot be instructed to or relied upon to sit quietly and attentively while experimenter-manipulated images and sounds are presented to him/her. Add to that the intrusion of a cotton swab into the infant’s and the mother’s mouths for several minutes, twice, the infant’s separation from the comfort and safety of mother’s arms, the varied types of stimuli and experimental paradigms used across phases of the study—and it becomes easy to see how an unwelcome guest, variability, might send an otherwise organized data pattern into disarray. With this in mind, we find it quite remarkable that there is indeed a coherent set of results to report, and a fascinating story to tell from these patterns of results.