James Mark Baldwin, answered from the texts and cited to the page.
The ego and the alter are not two things that meet; they are two poles of one growth, born in the same moment and by the same process. Watch how it happens. The child begins with what I call the projective stage: persons around him are bodies that move, objects among objects, but with a peculiar and interesting character he cannot yet name.1
The instrument of transition out of that stage is his own active body and the function of imitation; when the organism is ripe for new accommodations, the child begins imitating persons, and in that effort discovers something his own body alone possesses — strains, stresses, resistances, pains, an inner felt series added to the outer imitative one.2
It is the experience of effort, specifically, that draws the great line of cleavage in his experience and separates off what is now first really subjective; the projective becomes subjective, and the self-notion is born.3 But the movement does not stop there. The child's new subject-sense goes out again by a return dialectic to illuminate the other persons around him.
The projective content of the earlier period is now lighted up, claimed, clothed on with the raiment of selfhood by analogy with the subjective: other people's bodies, says the child to himself, have experiences in them such as mine has — they are also me's, to be assimilated to his me-copy.4 This is the ejective stage, and with it the social self is born.
So the ego and the alter are born together, both crude and unreflective, largely organic, an aggregate of sensations prime among which are efforts, pushes, strains, physical pleasures and pains.5 And the two get purified and clarified together by a twofold reaction: between project and subject, and between subject and eject. My sense of myself grows by imitation of you, and my sense of yourself grows in terms of my sense of myself.6
Each is a socius; each is an imitative creation. The circumference of the child's self-notion is, for a long time, too wide — it literally includes his mother, his nurse, his little brother, for they are what he thinks of and aims to act like when he thinks of himself; to be separated from his mother is to lose a part of himself, as much so as to be separated from a hand or foot.7
This give-and-take between the individual and his fellows I named the Dialectic of Personal Growth, and it serves as the point of departure for everything I developed in the theory of the social self.8 The philosophical consequence is plain: it is impossible to isolate a person's thought of himself at any time and say that in thinking of himself he is not already thinking of others.9
There is no private ego prior to society; the very selfhood one calls one's own is a deposit of the social relation, built up by imitation and returned to the social world that made it.
A person stands for a group of experiences quite unstable in its prophetic as it is in its historical meaning. This we may, for brevity of expression, assuming it to be first in order of development, call the 'projective stage' in the growth of the child's personal consciousness.Social and Ethical Interpretations in Mental Development
Further observation of children shows that the instrument of transition from such a projective to a subjective sense of personality is the child's active bodily self, and the method of it is the function of imitation... it has connected with it certain intimate features which all others lack — strains, stresses, resistances, pains, etc., an inner felt series added to the new imitative series.Social and Ethical Interpretations in Mental Development
It is only when a peculiar experience arises which we call effort that there comes that great line of cleavage in his experience which indicates the rise of volition, and which separates off the series now first really subjective. What has formerly been 'projective' now becomes 'subjective.'Social and Ethical Interpretations in Mental Development
The child's subject sense goes out by a sort of return dialectic to illuminate the other persons. The 'project' of the earlier period is now lighted up, claimed, clothed on with the raiment of selfhood, by analogy with the subjective. The subjective becomes ejective; that is, other people's bodies, says the child to himself, have experiences in them such as mine has.Social and Ethical Interpretations in Mental Development
The ego and the alter are thus born together. Both are crude and unreflective, largely organic, an aggregate of sensations, prime among which are efforts, pushes, strains, physical pleasures and pains.Mental Development in the Child and the Race
My sense of myself grows by imitation of you, and my sense of yourself grows in terms of my sense of myself. Both ego and alter are thus essentially social; each is a socius, and each is an imitative creation.Mental Development in the Child and the Race
For a long time the child's sense of self includes too much: the circumference of the notion is too wide. It includes the infant's mother, and little brother, and nurse, in a literal sense. To be separated from his mother is to lose a part of himself; as much so as to be separated from a hand or foot.Fragments in Philosophy and Science
This give-and-take between the individual and his fellows, looked at generally, we may call the Dialectic of Personal Growth. It serves as the point of departure for the main positions developed in the following pages.Social and Ethical Interpretations in Mental Development
If it be true, as much evidence goes to show, that what the person thinks as himself is a pole or terminus at one end of an opposition in the sense of personality generally, and that the other pole or terminus is the thought he has of the other person, the 'alter,' then it is impossible to isolate his thought of himself at any time and say that in thinking of himself he is not—Social and Ethical Interpretations in Mental Development