Huether (1998) has proposed that the human postnatal brain requires sufficient, but not excessive,psychosocial stress to promote optimal synaptic structure. A similar model of moderate intrauterine exposure in the promotion of optimal adaptation has been put forth by Amiel-Tison et al.(2004). Both echo the classic inverted U-shaped function of the relation between arousal and performance (Yerkes & Dodson, 1908). Although we did
not detect curvilinear associations in this study, this was a nonclinical sample and the upper threshold above which deleterious associations might emerge may not have been reached. However, the contrasting finding of lower MDI scores at the same age in an
earlier report (Brouwers et al., 2001) may be consistent with this interpretation.