## 4 Results and Discussions
### Building a Generalized Linear Model to Assess the Difficulty of E-C and C-E Translation Tasks
Importantly, interaction terms between AU_type and GazeEventDuration were tested in previous models but were found to be non-significant. This indicates that the effect of gaze duration on pupil dilation does not vary meaningfully across translation processing types in C-E translation. As a result, we report the final model without interaction terms for a more parsimonious interpretation. The results, presented in Table 5, indicate that translation processing type impacts cognitive load differently in Chinese-to-English translation. Unlike in E-C translation, where ST significantly reduced pupil dilation, in C-E translation, ST processing does not significantly differ from parallel processing (\(p\) = 0.285). However, TT processing leads to a significant decrease in pupil dilation (\(p\) < 0.001), suggesting lower cognitive effort during text production compared to multitasking (parallel processing). A key distinction from the E-C results is that gaze event duration significantly influences pupil dilation in C-E translation (\(p\) < 0.001). Longer fixation durations are associated with increased pupil dilation, suggesting that sustained fixations demand higher cognitive effort in this translation direction. However, no significant interaction effects between gaze event duration and AU_type were observed, indicating that the impact of fixation duration on pupil dilation remained \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Predictor** & **Estimate** & \(p\)**-Value** & **Interpretation** \\ \hline Intercept & 3.138 & \textless{}0.001 *** & Baseline pupil dilation (parallel processing, reference participant). \\ \hline AU\_typeST & \(-\)0.0356 & \textless{}0.001 *** & ST processing significantly reduces pupil dilation compared to parallel processing. \\ \hline AU\_typeTT & \(-\)0.0140 & 0.033 * & TT processing slightly reduces pupil dilation relative to parallel processing. \\ \hline GazeEventDuration & \(-\)0.000028 & 0.026 * & Longer gaze durations are associated with a small but significant decrease in pupil dilation. \\ \hline AU\_typeST:GazeEventDuration & \(-\)0.000018 & 0.265 & Not significant: gaze duration does not significantly alter pupil dilation in ST processing. \\ \hline AU\_typeTT:GazeEventDuration & 0.000039 & 0.0026 ** & Significant: longer gaze durations increase pupil dilation in TT processing. \\ \hline \end{tabular}
\end{table} 
Table 4: Interpretation of Gaussian model for English-to-Chinese translation, with a corresponding estimate and \(p\)-value with Signif. codes: ******* 0.001 *** 0.01 * 0.05.  
stable across all translation processing types. Additionally, participant differences were highly significant across all models (_p_ < 0.001), demonstrating individual variability in cognitive processing strategies. Some participants, such as P09, exhibited higher pupil dilation, whereas others, such as P18 and P13, showed reduced pupil dilation, indicating variability in cognitive load management. However, due to the complexity and secondary relevance of these variations, we omit a detailed discussion of participant differences. The findings from our Generalized Linear Models (GLMs) highlight key differences in cognitive load between English-to-Chinese (E-C) and Chinese-to-English (C-E) translation. In E-C translation, ST processing significantly reduces pupil dilation, indicating that comprehension requires less cognitive effort than multitasking (parallel processing). Additionally, longer gaze durations generally decrease pupil dilation, except in TT processing, where sustained fixations increase cognitive load. In contrast, C-E translation exhibits a different pattern, where ST does not significantly differ from parallel processing, and TT processing still reduces cognitive effort. Notably, longer gaze event durations significantly increase pupil dilation across all processing types, suggesting that sustained fixations in C-E translation may indicate greater cognitive effort.