I have reviewed some experimental studies which deal with the issue of the infant's control over environmental events, the infant's joy when it discovers that an external event is contingent upon its activity, and the corresponding trauma of being unable to influence, predict or comprehend an event which the infant expected on the basis of previous experience to be able to control or understand. This joy in being a cause seems a clear expression of what White called effectance pleasure. I regard the sense of efficacy as the core of the developing sense of self and traumatic disturbances in the sense of efficacy as core narcissistic injuries which predispose to significant psychopathology in the course of development.