CHAPTER VI Motor Development

THE past three years have produced nothing of importance in the investi-gation of motor development in infancy or early childhood. Much has been added to knowledge of adolescent changes in motor performances, how-ever. The war provided impetus for experimentation in the measurement of physical fitness of high school and young adult age groups. Emphasis in this area has been placed upon changes brought about by training. The availability for experimentation of large numbers of men in the twenty-one to forty age group has thrown light on motor changes in these years, also. Age Changes and Sex Differences in Adolescence Growth in fine motor abilities in adolescent boys and girls has been re-ported by Jones and Seashore (31). In some functions, as reaction time, growth has apparently reached its limit by fifteen years while in others as serial discrimination, the gain at fifteen is as great as in previous years. For the battery as a whole, girls are slightly retarded as compared wit