Her major contributions to psychoanalytic thinking dealt with the development of the sense of identity and self-esteem and with an understanding of depression and psychosis.

[2] In 1930, she became a member of the Berlin Psychoanalytic Society and was soon presenting papers that dealt with her interest in the problems of the superego and its development.

[2] She built on the contributions of Anna Freud, Heinz Hartmann, René Spitz, and Margaret Mahler.

In 1964, she wrote The Self and the Object World, in which she revised Sigmund Freud's theory about the psychosexual phases in the development, and his conceptualizations of id, ego, and superego.

In Freud's point of view, drives were innate, while the ego psychologists emphasized the influence of the environment.

[6] A balance in subjective feeling states in the early experiences of the child will contribute to the harmonious development of the libido and aggressive drive.

Jacobson proposed – in agreement with René Spitz – that experiences, whether they are good or bad, will accumulate in a child's psyche.

These earliest images form the groundwork for later subjective feelings of self and others and will serve as a filter through which one will interpret new experiences.

[7] Gradually, the aggressive and libidinal components also become more differentiated, which leads to new structural systems: the ego and the superego.

However, a lack of balance between libido and aggression could lead to weak boundaries between self and other, which can be observed in psychotic patients.

[13] With regard to the development of the Ego and Superego Jacobson stressed the role of parental influence as crucial.