In the sphere of impulse and emotion the same kinds of modification occur. Detachment of an impulse or emotion from its natural stimulus is very much in evidence, since {300} what frightens or angers or amuses the little child may have no such power with the adult. One little boy of two could be thrown into gales of laughter by letting a spoon drop with a bang to the floor; and you could repeat this a dozen times in quick succession and get the response every time. But this stimulus no longer worked when he had advanced to the age of four.

The emotions get attached to substitute stimuli. Amusement can be aroused in an older child by situations that were not at all amusing to the baby. New objects arouse fear, anger, rivalry or curiosity. The emotions of the adult--with the exception of sex attraction, which is usually very weak in the child--are the emotions of the child, but they are aroused by different stimuli.

Not only so, but the emotions express themselves differently in the child and the adult. Angry behavior is one thing in the child, and another thing in the adult, so far as concerns external motor action. The child kicks and screams, where the adult strikes with his fist, or vituperates, or plots revenge. The internal bodily changes in emotion are little modified as the individual grows up--except that different stimuli arouse them--but the overt behavior is greatly modified; instead of the native reactions we find substitute reactions.

A little girl of three years, while out walking in the woods with her family, was piqued by some correction from her mother, but, instead of showing the instinctive signs of temper, she picked up a red autumn leaf and offered it to her mother, with the words, very sweetly spoken, "Isn't that a pretty leaf?" "Yes," said her mother, acquiescently. "Wouldn't you like to have that leaf?" "Yes, indeed." "I'll throw it away!" (in a savage tone of voice, and with a gesture throwing the leaf away). Here we have an early form of substitute reaction, and can glimpse how such {301} reactions become attached to the emotions. The natural outlet for the child's anger was blocked, probably because previous outbursts of rage had not had satisfactory consequences, so that the anger was dammed up, or "bottled up", for the instant, till the child found some act that would give it vent. Now supposing that the substitute reaction gave satisfaction to the child, we can well imagine that it would become attached to the angry state and be used again in a similar case. Thus, without outgrowing the emotions, we may outgrow emotional behavior that is socially unacceptable.

Emotions are also combined, much as reflexes are combined. The same object which on one occasion arouses in us one emotion may arouse another emotion on another occasion, so that eventually, whenever we see that object, we respond by a blend of the two emotions. Your chief may terrify you on some occasions, at other times amaze you by his masterly grasp on affairs, and again win your affection by his care for your own welfare; so that your attitude toward "the boss" comes to be a blend of fear, admiration and gratitude. Religion and patriotism furnish good examples of compound emotions.

Well, then, adult behavior compared with the instinctive behavior of the little child shows these several types of modification. This is interesting, but it is not all we wish to know. We want to know how the modification comes about; that is, we want to get an insight into the process of learning. Scientifically, this is one of the most fascinating topics in psychology--how we learn, how we are molded or modified by experience--and practically, it is just as important, since if we wish to educate, train, mold, improve ourselves or others, it is the process of modification that we must control; and to control it we must understand it.

To understand it we must watch the process itself; and {302} therefore we turn to studies that trace the course of events in human and animal learning.