Masturbation: Infancy through Preschool Age
by Dr. Benjamin Spock
reviewed and revised by Robert Needlman, M.D., F.A.A.P.
All babies take great, uninhibited pleasure in their bodies, especially in certain areas like the mouth and genitals. They eat with gusto, smacking their lips when sated, raising a ruckus when hungry. It is with unabashed pleasure that they delight in the pleasures of their body--being held, stroked, kissed, tickled, massaged. The pleasure principle reigns unapologetically supreme.
Masturbation is part of the normal development of sexuality in children. Of course, sexual feelings are different in young children than in adults. The difference is that adults tend to focus more on their genitals. Adults also attach a great deal of psychological meaning to things sexual.
You could say that infants have sensual feelings rather than sexual feelings, because infant sexuality is not focused on the genitals.