This interest goes on to develop very rapidly in the second half year, in connection more particularly with the movements which are associated with the child's own comfort and discomfort.

The association of muscular sensations with those of touch and sight serves to give him his first clear indications of the positions of his own members and of other objects.

His discrimination of what belongs to his own body is probably aided by so-called "double touch"-- the fact that when he touches his own body, as in touching his foot with the hand, he has two sensations, one in the foot and the other in the hand.

This is not the case when he touches other objects, and he soon learns the distinction, getting the outlines of his own body marked out in a vague way.

The learning of the localities on his body which he can not see, however, lags far behind.