The course for this period will concentrate the effort upon fewer lines," and more time will be devoted to each. The desire for mastery is now at its height. The instinct is to maintain one's self independently and ask no odds. At fourteen, especially, the impulse is, in manual training, to make something and perhaps to coöperate. McGhee[7] collected the play preferences of 15,718 children, and found a very steady decline in running plays among girls from nine to eighteen, but a far more rapid rise in plays of chance from eleven to fifteen, and a very rapid rise from sixteen to eighteen. From eleven onward with the most marked fall before fourteen, there was a distinct decline in imitative games for girls and a slower one for boys. Games involving rivalry increased rapidly among boys from eleven to sixteen and still more rapidly among girls, their percentage of preference even exceeding that of boys at eighteen, when it reached nearly seventy per cent. With adolescence, specialization upon a few plays was markedly increased in the teens among boys, whereas with girls in general there were a large number of plays which were popular with none preëminent. Even at this age the principle of organization in games so strong with boys is very slight with girls. Puberty showed the greatest increase of interest among pubescent girls for croquet, and among boys for swimming, although baseball and football, the most favored for boys, rose rapidly. Although the author does not state it, it would seem from his data that plays peculiar to the different seasons were most marked among boys, in part, at least, because their activities are more out of doors.