Comprehension aids for on-line reading of expository text

A chapter of expository text was presented on a CRT with optional "windowing" of definitions of selected words varying in relevance to each screen's main ideas. A test treatment was interposed to influence reading strategies. Dependent variables included text reading time, frequency of definition "calls," definition reading rates, and scores on a final comprehension test. Results indicate that a technical chapter can be read from a CRT with appreciable content retention. Subjects accessed 80% of available definitions, but those able to "call" content-relevant definitions increased their frequency of definition "calls." Definition reading rate diminished; comprehension and processing time increased only for subjects accessing the theoretically relevant definitions. The results suggest how the use of definitions enhances the comprehension of on-line training manuals, texts, and help screens. "Callable" definitions need not include all low-frequency technical concepts but only those relevant to reductive main ideas.