Finally, an important type of modification consists in the _combination_ of reflex movements into larger coördinations. One hand grasps an object, while the other hand pulls, pushes or strikes it. Or, both hands grasp the object but in different ways, as in handling an ax or shovel. These cases illustrate simultaneous coördination, and there is also a serial coördination, in which a number of simple instinctive movements become hitched together in a fixed order. Examples of this are seen in dancing, writing a word, and, most notably, in speaking a word or familiar phrase. In these ways, by strengthening, fixing and combining movements, and by new attachments and detachments between stimulus and response, the instinctive motor activity of the baby passes over into the skilled and habitual movement of the adult. Acquired Tendencies 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.