1The following four aspects of motility were discussed as being of special psychological interest in infants and children: (a) affectomotor patterns; (b) well-organized, vigorous rhythmic patterns, usually referred to as autoerotic; (c) skilled motor activities; and (d) motor phenomena that are indispensable elements in the function of other organs.

2These various functions may be fused in the concept of a motor drive which follows a developmental scheme both as a whole and as regards its component parts, the second year of life, with some extension, being the motor phase of ego and libido development (i.e., motility being the dominant source of pleasure and mastery). This paper deals mainly with the affectomotor and the vigorous rhythmic phenomena and their pathological implications.