Results from the session-comparison questionnaire. From left to right, the panels show the results for questions 1, 2, 3, and 4 in the session-comparison questionnaire (Figure 4, right). Those questions concern respectively general fatigue, eye irritation, headache, and a general preference for one condition over another. The conditions being compared are natural viewing and S3D viewing. A comparison score of 5 means no difference between the two. Scores greater than 5 mean that S3D viewing caused more severe symptoms or was less preferred. Scores less than 5 mean the opposite. The double asterisks indicate a significant difference from 5 (p<0.05, Wilcoxon signed-rank test, two-tailed). Single asterisk indicates marginally significant difference from 5 (p<0.1).