The orgasm in an infant or other young male is, except for lacking of ejaculation, a striking duplicate of orgasm in an older adult. The behavior involves a series of gradual physiologic changes, the development of rhythmic body movements with distinct penis throbs and pelvic thrusts, an obvious change in sensory capacities, a final tension of muscles, especially of the abdomen, hips, and back, a sudden release with convulsions, including rhythmic anal contractions—followed by the disappearance of all symptoms. A fretful baby quiets down under the initial sexual stimulation, is distracted from other activities, begins rhythmic pelvic thrusts, becomes tense as climax approaches, is thrown into convulsive action, often with violent arm and leg movements, sometimes with weeping at the moment of climax. (Kinsey et al., 1948, p. 177)
It is impossible to determine what such early sexual experiences mean to infants, but it is reasonably certain that these activities are gratifying. Many infants of both sexes engage quite naturally in self-pleasuring unless such behavior produces strong negative responses from parents or other caregivers.
Clearly, an infant is unable to differentiate sexual pleasure from other forms of sensual enjoyment. Many of the natural everyday activities involved in caring for an infant, such as breast-feeding and bathing, involve pleasurable tactile stimulation that, although essentially sensual in nature, produces a genital or sexual response (Frayser, 1994; Martinson, 1994).