Sometimes the father smiles and tosses the child; sometimes he does not.

Even the indulgence of the grandmother has its times and seasons.

The child looks for signs of these varying moods and methods of treatment; for his pains of disappointment arise directly on the basis of that former sense of regular personal presence upon which his expectancy goes forth.
This new element of the child's sense of persons becomes, at one period of its development, quite the controlling element.

His action in the presence of the persons of the household becomes hesitating and watchful.

Especially does he watch the face, for any expressive indications of what treatment is to be expected; for facial expression is now the most regular as well as the most delicate indication.
Special observations on H.'s responses to changes in facial expression up to the age of twenty months showed most subtle sensibility to these differences; and normal children all do.