=To Modify a Habit.=--At other times, however, we may desire not to eliminate an habitual co-ordination _in toto_, but rather to modify only certain phases of the reaction. In writing, for instance, a pupil may be holding his pen correctly and also using the proper muscular movements, but may have developed a habit of forming certain letters incorrectly, as [symbol] and [symbol]. In any attempt to correct such forms, a special difficulty is met in the fact that the incorrect movements are now closely co-ordinated with a number of correct movements, which must necessarily be retained while the other portions of the process are being modified. To effect such a modification, it is necessary for attention to focus itself upon the incorrect elements, and form a clear idea of the changes desired. With this idea as a conscious aim, the pupil must have abundant practice in writing the new forms, and avoid any recurrence of the old incorrect movements. This fact emphasizes the importance of attending to the beginning of any habit. In teaching writing, for instance, the teacher might first give attention only to the form of the letter and then later seek to have the child acquire the muscular movement. In the meantime, however, the child, while learning to form the letters, may have been allowed to acquire the finger movement, and to break this habit both teacher and pupil find much difficulty. By limiting the child to the use of a black-board or a large pencil and tablet, and having him make only relatively large letters while he is learning to form them, the teacher could have the pupil avoid this early formation of the habit of writing with the finger movement.