This focus is consistent with Levine’s (2005) argument that lack or loss of species typical parental stimulation is among the most potent stressors early in life. A focus on deprivation or loss as a potent stressor is consistent with Hofer’s (1994) concept of hidden regulators embedded in parent-offspring relationships. He has argued that a number of sensorimotor, thermal, and nutrient-based events that are components of typical parent-offspring interactions have long-tem regulatory effects on specific components of infant behavior and physiology. Loss of these hidden regulators results in wide-spread dysregulation of physiological and behavioral responses during development resulting in disturbances in circadian rhythms, growth (including brain growth factors, e.g. Cirulli et al., 2000) and hormone levels (including activity of the hypothalamic-pituitary-adrenocortical [HPA] axis, e.g. Rosenfeld et al.,1992). Animal studies also point to circuits involved in threat- and stress-system functioning as particularly sensitive to disturbances in parental nurturance (see review, Sanchez et al., 2001). Importantly, though, recent rodent studies also indicate that later interventions may help ameliorate some (but not all) of the impact of poor early nurturance (Bredy et al., 2003;
