A within-subjects analysis was used to reduce any variability that may have been attributed to differences between subjects: thus, each subject’s performance on one layout was compared with his or her own performance on an alternative layout. The practice diagrams and the randomisation of the order of presentation of the experimental diagrams for each subject helped counter the learning effect (whereby subjects’ performance on the task may improve over time, as they become more competent in the task). The response time and accuracy of the subjects’ responses to the 32 experimental diagrams were recorded by the online system
