At what stage does an infant begin to differentiate between “I” and “not-I” according to Mahler?

The correct answer reflects a significant developmental milestone in Mahler's theory of object relations, specifically during the separation-individuation phase. Around 2 to 3 months, infants start to develop a sense of self that distinguishes themselves from their caregivers and the external world. This stage is crucial for the infant’s developing identity, as they begin to recognize that they are separate individuals ("I") from others ("not-I").

During this time, infants engage in behaviors such as increased visual tracking and social interaction, which help them form an understanding of the distinction between themselves and others. This recognition marks the beginning of self-awareness and is foundational for later emotional development and attachment processes.

In contrast, at birth, an infant is in a state of undifferentiated existence, wholly reliant on the caregiver without any sense of individual identity. By 4 months, the differentiation process becomes more pronounced but is fully realized later as the infant continues to develop. The assertion that differentiation occurs at 3 years is too late for the initial stages of this important developmental process, as significant advances in self-concept and socialization occur well before that age. Thus, the period of 2 to 3 months is critical in the context of Mahler's understanding of infant development