This paper, one of a series of reports on the findings of an investigation of sexual development in the second year of life,

examines systematically a set of hypotheses which had been developed by Roiphe earlier. 1. All children between the ages of fifteen and twenty-four months normally show evidence of a sexual arousal as indicated by a sharp increase in the manipulation of the genitals, including frank masturbatory activity; they also show evidence of sexual curiosity, particularly about the anatomical difference between the sexes. 2. Children in the second year of life who have already experienced such sexual arousal and who have had the occasion to observe the difference between the sexes will develop distinct castration reactions provided there have been earlier experiences which tend to produce an unstable body image or experiences which tend to result in an unstable object representation.