## 3 Results and Discussion
### Results of Reading Comfort Assessment  
According to the results of the Mann-Whitney U test, no significant difference was found between the reading comfort ratings of experienced subjects (Group A) and inexperienced subjects (Group B) in Exp.2. Thus, no practice effect was found and the data in Exp.2 were combined.  
The effects of paper colour, lighting environment, test trial, as well as gender, on reading comfort were investigated using a MANOVA test (Table 4). The hypothesis was that paper colour, lighting environment, and their interaction effect might have a significant impact on the rating of reading comfort. As shown in Table 4, however, only paper colour exhibited a significant influence (\(p\) < 0.001, with the largest \(\eta^{2}\) value) and the impact of lighting was insignificant.  
The results of the MANOVA test also show that no other effects of gender and test trial (including interaction effects) were significant. Thus, it can be concluded that visual fatigue does not have a significant impact on reading comfort assessments. It should also be noted that the \(p\) value for gender was only slightly higher than 0.05 (0.052), which is consist with the results in Section 3.1 above. This finding further suggests that the effect of gender should not be underestimated and deserves further investigation.  
The post hoc test for the significant main effects (paper colour) revealed that the comfort ratings amongst different paper colours were significantly different at the 95% confidence level: \(p\) < 0.001 for white paper vs. yellowish-white paper; \(p\) = 0.005 for white paper vs. green paper; \(p\) < 0.001 for yellowish-white paper vs. green paper.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Fixed Factors** & **Mean Square** & **F** & \(p\)**-Value** &
\begin{tabular}{c} **Partial Eta** \\ **Squared, \(\eta^{2}\)** \\ \end{tabular} \\ \hline Paper colour & 44.545 & 25.389 & \textless{}0.001 & 0.101 \\ Lighting environment & 0.161 & 0.092 & 0.762 & 0.000 \\ Test trial & 4.594 & 2.619 & 0.106 & 0.006 \\ Gender & 6.635 & 3.782 & 0.052 & 0.008 \\ Paper colour \(\times\) Lighting environment & 2.101 & 1.197 & 0.303 & 0.005 \\ Paper colour \(\times\) Test trial & 2.712 & 1.546 & 0.214 & 0.007 \\ Paper colour \(\times\) Gender & 2.792 & 1.590 & 0.205 & 0.007 \\ Lighting environment \(\times\) Test trial & 2.294 & 1.305 & 0.254 & 0.003 \\ Lighting environment \(\times\) Gender & 0.092 & 0.052 & 0.819 & 0.000 \\ Test trial \(\times\) Gender & 0.276 & 0.157 & 0.692 & 0.000 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Results of MANOVA for the subjective ratings for reading comfort.  
Figure 10: The means of the subjects’ proofreading speed and accuracy in Exp.1 and in Exp.2 after removing the practice effect. The error bars depict the 95% confidence intervals.  
Figure 11 illustrates the average scores of the comfort rating and the results of a Wilcoxon Signed Rank Test, which was used to further verify the impact of paper colour on perceived reading comfort in Exp.1 and Exp.2. The results showed that the yellowish-white paper was related to the most comfortable reading experience (\(p\) values \(<\) 0.05), while the white paper was rated as least comfortable.  
Another finding of interest is that the average comfort rating score for green paper increases significantly after the 2-h self-study session (\(p\) = 0.007) in Exp.1, which was not found in Exp.2 (in Exp.2, the increment does exist but is not significant). This result could be related to the interaction between the lighting environment and the visual perception of green paper, which should be further clarified by future work.