Based on psychoanalytic concepts, Mahler presented three stages of development in the preoedipal phase of an infant (first 2 or 3 years) with the third stage broken down into 4 sub-categories:

1. Normal Autistic (newborn to 1 month) - baby is only aware of his/or her own needs.

2. Normal Symbiosis (1-5 months) - fusion with mother occurs.

3. Separation-Individuation:

a. Differentiation (5-10 months) - baby may develop separation anxiety; needs reassurance that mother is still there even when not in view.
b. Practicing motor skills (10-16 months) - baby attempts crawling and exploring short distances away from mother; baby is most comfortable playing with mother in view.
c. Rapprochement (16-24 months) - "ambitendency" (child discovers that he/or she is an individual separate from mother which is both exciting and scary; e.g. child may run away from mother and defy her instructions but then come running right back and want to be held).
d. Constancy of self and object (24-36 months) - child develops "object constancy" - even though object is not in view, it still exists; because of this, separation from mother becomes a little bit easier.