Printed text is designed to be linear. We begin at the beginning, and proceed to the end. This is a good strategy while building a base of knowledge on a topic. Once that base is built, the strategy shifts to filling in the holes and selectively expanding what we know. This is non-linear learning. The index and the reference manual meet this need in print. The computer is optimized for non-linearity, and the early development of hypertext is the best example. The brain's internal wiring is non-linear. Our thinking constantly branches off in diverse directions as incoming information is processed. We can take advantage of this to defeat information overload.