The modality effect occurs when audio/visual instructions are superior to visual only instructions. The effect was explored in two experiments conducted within a cognitive load theory framework. In Experiment 1, two groups of primary school students (N = 24) were presented with either audio/visual or visual only instructions on how to read a temperature graph. The group presented with visual text and a diagram rather than audio text and a diagram was superior, reversing most previous data on the modality effect. It was hypothesized that the reason for the reversal was that the transitory auditory text component was too long to be processed easily in working memory compared to more permanent written information. Experiment 2 (N = 64) replicated the experiment with the variation of a reduced length of both auditory and visual text instructions. Results indicated a reinstatement of the modality effect with audio/visual instructions proving superior to visual only instructions. Copyright © 2011 John Wiley & Sons, Ltd.