Toddlers' acquisition of self/other knowledge: ecological and interpersonal aspects of self and other

The complexity of toddlers' self-development was examined in the context of knowing others. Two studies were designed to test whether toddlers' self-knowledge was different from their knowledge of others (e.g., mother and inanimate object) or whether toddlers' knowledge of persons (e.g., self and mother) was different from their knowledge of objects. Knowledge of self, mother, and inanimate object was observed in developmentally sequenced tasks assessing agency and featural knowledge. When the inanimate object was perceptually different from humans, 12-month-old toddlers responded differently to all 3 versions. When the inanimate object was perceptually similar to humans, 24-month-olds distinguished self from other and did not distinguish between the 2 versions of "other:" mother and inanimate object. We concluded that 12-month-old infants were more sensitive to perceptual features of objects than were older toddlers. Data were interpreted according to Neisser's distinction between the ecological self and the interpersonal self.