in handling tools.  However, there is no sharp line of division between these various unlearned tendencies; what one psychologist calls a reflex or a series of reflexes, another will call an instinct.  It seems better to consider them as of the same general character but differing from each other in simplicity, definiteness, uniformity of response, variableness among individuals, and modifiability.  They range from movements such as the action of the blood vessels to those concerned in hunting and collecting; from the simple, definite, uniform knee-jerk, which is very similar in all people and open to very little modification, to the capacity for scholarship, which is extremely complex, vague as to definition, variable both as to manifestation in one individual and amounts amongst people in general, and is open to almost endless modification.  This fund of unlearned tendencies is the capital with which each child starts, the capital which makes education and progress possible, as well as the capital which limits the extent to which progress and development in any line may proceed.” The Psychology of Childhood, pp. 21, 22, 23.

Weigle, in his Talks to Sunday School Teachers, begins his second chapter in a rather unique and helpful manner relative to this same question: 

“The little human animal, like every other, is born going.  He is already wound up.  His lungs expand and contract; his heart is pumping away; his stomach is ready to handle food.  These organic, vital activities he does not initiate.  They begin themselves.  The organism possesses them by nature.  They are the very conditions of life.

“There are many other activities, not so obviously vital as these, for which nature winds him up quite as thoroughly—­yes, and sets him to go off at the proper time for each.  He will suck when brought to the breast as unfailingly as his lungs will begin to work upon contact with the air.  He will cry from hunger or discomfort, clasp anything that touches his fingers or toes, carry to his mouth whatever he can grasp, in time smile when smiled at, later grow afraid when left alone or in the dark, manifest anger and affection, walk, run, play, question, imitate, collect things, pull things apart, put them together again, take pleasure in being with friends, act shy before strangers, find a chum, belong to a ‘gang’ or ‘bunch,’ quarrel, fight, become reconciled, and some day fall in love with one of the opposite sex.  These, and many more, are just his natural human ways.  He does not of purpose initiate them any more than he initiates breathing or heart-beat.  He does these things because he is so born and built.  They are his instincts.”

As Norsworthy and Whitley point out, we are not especially concerned with the boundary lines between automatic actions, reflexes, and instincts—­we are rather concerned with the fact that human beings possess native tendencies to act in particular ways.  Some psychologists stress them as instincts; others as capacities, but they have all pretty generally agreed that under certain stimuli there are natural tendencies to react.