In trying to trace the emergence of the sense of self during the first fifteen months of life—in particular the formation of the bodily self—we used, on the one hand, severe dissociations of the integral parts of the body self such as occurs in psychosis, in the Gilles de la Tourette syndrome, and in phantom-limb disturbances and, on the other hand, data from our normative study of the separation-individuation process as inferred from mother-infant interaction in general and the infant's behavior in front of the mirror in particular.

The infant's behavior in front of the mirror strongly suggests that feelings about himself only gradually become integrated with perceptual and cognitive awareness of himself. All the data, furthermore, indicate that it is not possible to study the development of the self separate from the development of the object.