In the accomplishment of this end it will be necessary to apply the principles of habit formation already described. Start out by making a strong determination to ignore all distractions. Practise ignoring them, and do not let a slip occur. Try to develop interest in the object of attention, because we pay attention to those things in which we are most interested. A final point that may help you is to use the first lapse of attention as a reminder of the object you desire to fixate upon. This may be illustrated by the following example: Suppose, in studying a history lesson, you come upon a reference to the royal apparel of Charlemagne. The word "royal" might call up purple, a Northwestern University pennant, the person who gave it to you, and before you know it you are off in a long day-dream leading far from the history lesson. Such migrations as these are very likely to occur in study, and constitute one of the most treacherous pitfalls of student life. In trying to avoid them, you must form habits of disregarding irrelevant ideas when they try to obtrude themselves. And the way to do this is to school yourself so that the first lapse of attention will remind you of the lesson in hand. It can be done if you keep yourself sensitive to wanderings of attention, and let the first slip from the topic with which you are engaged remind you to pull yourself back. Do this before you have taken the step that will carry you far away, for with each step in the series of associations it becomes harder to draw yourself back into the correct channel. In reading, one frequent cause for lapses of attention and for the intrusion of unwelcome ideas is obscurity in the material being read. If you trace back your lapses of attention, you will often find that they first occur when the thought becomes difficult to follow, the sentence ambiguous, or a single word unusual. As a result, the meaning grows hazy in your mind and you fail to comprehend it. Naturally, then, you drift into a channel of thought that is easier to follow. This happens because the mental stream tends to seek channels of least resistance. If you introspect carefully, you will undoubtedly discover that many of your annoying lapses of attention can be traced to such conditions. The obvious remedy is to make sure that you understand everything as you read. As soon as you feel the thought growing difficult to follow, begin to exert more effort; consult the dictionary for the meanings of words you do not understand. Probably the ordinary freshman in college ought to look up the meaning of as many as twenty words daily.