or emotional—­all are manifestations of this tendency towards activity.  All habits of all kinds grow out of this same activity:  habits which we call work and those which we call play.  Man has not two original natures, one defined in terms of the play instinct, and the other in terms of work.  Most of the original tendencies involved in play are not peculiar to it, but also are the source of work.  Manifestation results in making “mud pies and apple pies”; physical activity results in the kicking, squirming, and wriggling of the infant and the monotonous wielding of the hammer of the road mender.  The conditions under which an activity occurs, its concomitants, and the attitude of the individual performing it determine whether it is play or work—­not its source or root.

Much, then, of what we call play is simply the manifestation of instincts and capacities not immediately useful to the child.  If they were immediately useful, they would probably be put under the head of work, not play.  Many of the activities which seem playful to us and not of immediate service do so because of the conditions of civilized life.  Were the infants living under primitive conditions, “in such a community as a human settlement seems likely to have been twenty-five thousand years ago, their restless examination of small objects would perhaps seem as utilitarian as their fathers’ hunting."[13] Certainly the tendency of little children to chase a small object going away from them, and to run from a large object approaching slowly, their tendency to collect and hoard, their tendency to outdo another engaged in any instinctive pursuit, would under primitive conditions have a distinct utilitarian value, and yet all such tendencies are ranked as play when manifested by the civilized child.

Other tendencies become playful rather than useful because of the complexity of the environment and of the nervous system responding to it.  In actual life we don’t find activity following a neatly arranged situation—­response system.  On the contrary, a situation seldom stimulates one response, and a response seldom occurs in the typical form required by theory.  It is this mingling of responses brought about by varying elements in the situation that gives the playful effect.  In a less complex environment this complexity would be lessened.  Also experience, habit, tends to pin one type of response to a given situation and the minor connections gradually become eliminated.  For example, if a boy of nine, alone in the woods, was approached by another with threatening gestures and scowls, the fighting response would be called out, and we would not call it play, because it served as protection.  If the same boy in his own garden, with a group of companions, was approached by another with scowls, a perfectly good-natured tussle might take place and we would call it play.  The difference between the two would be in minor elements of the situation.  Some of these differences are absence or presence of companions, the strangeness or familiarity of the surroundings, the suddenness of the appearance of the other boy, and so on.