Implications of three basic facts about very young infants are delineated in this summary. Normally, human infants are capable of a wide range of functions, such as "appetitive responses" (e.g., the rooting reflex) and defensive maneuvers. They experience pleasure and feel pain. Additionally, they undergo a transition from subcortical to cortical functioning that is developmentally critical. As a result of various conditions, fundamental abilities of infants may be compromised. With severe consequences for emotional development, infants may fail to learn that their behavior is instrumental in arranging the environment for pleasure and for removing annoyances. Also, some infants may not successfully make the difficult transition from subcortical to cortical mediation. Since at the present time many infants born at risk with deficits and debilities survive, it is possible that individual differences are now larger than at any previous time in the history of mankind. Infants who are compromised physiologically through unfortunate histories of risk should be carefully studied to provide information concerning behavioral and neurophysiological change. Periods of confusion and disorganization during the transition to cortical mediation should also be studied in view of the fact that some 90 per cent of all crib deaths occur within the age period when behavioral perturbation often seems concentrated. (Author/RH)