Suppose that you grab an instructional manual, you may glance over some of the pages to determine whether it looks interesting enough to read carefully. Our past study demonstrated that illustrations enhance readers’ motivation in the first few seconds in text comprehension. This study examined the knowledge about the role of illustrations and the relationships to the motivation effect. In the first phase of this experiment, participants were required to glance over a page of a disaster prevention manual for two seconds and to answer questions as to motivation, such as “Did the page motivate you to read?” In the next phase, they were required to evaluate a subjective amount of information and comprehension efficiency for each page. Results showed that illustrations didn’t increase the subjective amount of information but subjective efficiency, which enhanced motivation to read.