The authors discuss the special problem of ego development which confronts identical twins. The study is based on the analytically oriented therapy of disturbed male twins, one of whom became psychotic. Both parents and an older brother were intensively interviewed and given projective tests.

Identical twins seem disposed to develop symbiotically without adequate ego boundaries between them. To mature they must differentiate from each other as well as from the mother. Problems of narcissism become complicated by the development of a primary object choice (the twin) who is also a mirror image; the narcissistic object choice increases homosexual trends. There is a tendency to divide roles, one twin becoming dominant and the other passive. The rivalry for the mother's affection creates intense ambivalence. As differentiation from the symbiotic state is difficult, ego development is hindered and loss of a sense of reality and psychosis may result.