Personal observation of the test situation together with questionnaire responses may provide an explanation for this. Many students were unfamiliar with the use of highlighters and found that with limited time available they were unable to concentrate on the learning task if they made full use of the highlighters. Consequently, a few students made little or no use of them, but of course these subjects were not excluded from their assigned groups. Others made comprehensive use of highlighters, but their progress was somewhat delayed by this and they failed to finish the text. We would expect this to be reflected in their test scores.
Data is available on the page reached by each student when their study time expired.
It would be interesting to examine their scores on test questions which dealt with material up to the point they reached. It is possible that they made slower progress but the quality of their learning was enhanced by using highlighters. In comparing the use of marginalia and highlighting it must be borne in mind that there are several basic differences between these methods of typographic signalling. Highlighting is the reverse of each of these characteristics. The reason subjects were asked not to re-read sections of the text, or make any notes, was so that the learning processes might be based on a single reading of the text.