There are an increasing number of studies assessing the early development of physiological and emotion self-regulation and the risk for psychopathology (Calkins & Dedmon, 2000; Calkins & Fox, 2002; Keenan, 2000; Shaw et al., 1997). The capacity to regulate emotion and behavior in early childhood has been shown to be extremely important in the development of adaptive and appropriate social behaviors in the preschool and school years (Calkins, 1994; Eisenberg et al., 1995, 1996). Children of parents with psychopathology are at greater risk for psychopathology and even in their infancy can exhibit behavioral differences from other children (Cohn & Tronick, 1983; Field, 1995).

Developmental psychopathology is a discipline that is organized around the incorporation of developmental principles into the study of the etiology of psychopathology. The program of research described in this chapter is informed by this framework and as a result is focused on this question: How early can we tell that a child is on a pathway toward deficient behavioral and emotional functioning? We propose that poorly modulated responses to stimuli in the first months of life may indicate risk for the development of later behavioral and emotional problems. In this chapter we present an overview of the theoretical underpinnings of this program of research, descriptive data on individual differences in the neonate's cortisol response to two different stressors, and an examination of the relations between behavior and cortisol response, with the goal of exploring how to operationally define suboptimal patterns of stress reactivity in human infants.