With the expansion of the World Wide Web and other electronic information sources, it is becoming increasingly important for learners to actively allocate their time among texts in order to maximize their learning. Finding relevant texts is no longer the main problem; rather the problem is one of adaptive time allocation among multiple relevant texts. What constitutes a good text is dependent on, among other things, the individual’s background knowledge, since comprehension requires textual information to be integrated with this knowledge so as to construct a situation model. If there is too much overlap between the text and the reader’s background knowledge, then the text affords little opportunity for learning, but if there is too little overlap then the text would be incomprehensible. Good texts for learning therefore fall in the middle ground that Wolfe, Schreiner, Rehder, Laham, Foltz, Kintsch & Landauer (1998) call the zone of learnability.