Evidence of erotic feelings in three female infants was first observed when they were less than 1 year of age. Masturbation was accomplished by friction of the thighs, rubbing the body against an object, or by manipulation. This was accompanied by grunting and flushing and progressed to what appeared to be an orgasm, followed by general relaxation, pallor, sweating, and sometimes a deep sleep.
Masturbation in male infants culminating in orgasm is discussed, as well as various views on eroticism in very young children and in primate infants.
Bakwin H. Erotic Feelings in Infants and Young Children. Am J Dis Child. 1973;126(1):52-54. doi:10.1001/archpedi.1973.02110190048009