# An Eye-Tracking Study on Text Comprehension While Listening to Music: Preliminary Results
## 2 Materials and Methods
### Data Preprocessing and Analysis  
Raw gaze data were collected and processed using Tobii Pro Eye-Tracker Manager (Tobii Pro X2-60) and iMotions 7.1 software to ensure data integrity and consistency. The preprocessing procedure involved multiple steps, including blink removal, where data points containing blinks or missing values were excluded from fixation calculations, and saccade filtering, where eye movements exceeding a velocity of 30\({}^{\circ}\)/s were classified as saccades and removed to isolate fixations. Additionally, fixation aggregation was performed by computing and averaging fixation durations and fixations count for each participant and reading condition. The Statistical Package for Social Sciences (SPSS) was utilized to analyze statistical differences across four visual patterns and two reading performance measures under the four auditory conditions: preferred music, non-preferred music, cafe noise, and silence. Statistical tests were conducted to examine how these four reading conditions (independent variable) influenced the measured dependent variables, which included fixation duration, fixations count, (TTFF), (FFD), reading time, reading comprehension, perceived difficulty, perceived understanding, perceived confidence, perceived fatigue, and perceived immersion. In order to decide on the suitable test to be performed, the assumptions of Analysis of Variance (ANOVA) were initially examined for all the related dependent variables. For each variable, the assumptions assessed included the independence of observations, normality (observations within each status should be normally distributed) and homogeneity of variance (variance of the observations within each status should be equal). In case all the assumptions were met, the ANOVA test is used, otherwise the non-parametric statistical test of Kruskal-Wallis is used to determine if there were statistical differences for the dependent variable between the independent reading status. The results of the ANOVA assumptions assessment are summarized in Table 1. For the variables fixation duration, fixations count and reading time, all the assumptions were met and ANOVA is used. For the rest of the variables, the normality assumption was violated, therefore the Kruskal-Wallis test was used. All analyses were corrected using the post hoc tests--the Bonferroni post hoc test after an ANOVA has been performed and the 'Dwass, Steel, Critchlow-Fligner' test after a Kruskal-Wallis test has been performed.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Independence of** & **Normality** & **Homogeneity of** & **ANOVA** & **Kruskal–Wallis** \\  & **Observations** & **Variance** & **ANOVA** & **Test** \\ \hline Fixation Duration (ms) & Yes & Yes & Yes & Yes & No \\ \hline Fixation Counts & Yes & Yes & Yes & Yes & No \\ \hline TTFF (ms) & Yes & No & No & No & Yes \\ \hline FFD (ms) & Yes & No & Yes & No & Yes \\ \hline Reading Comprehension (0–10 point scale) & Yes & No & No & No & Yes \\ \hline Reading Time (s) & Yes & Yes & Yes & Yes & No \\ \hline Perceived Difficulty & Yes & No & Yes & No & Yes \\ \hline Perceived Understanding & Yes & No & No & No & Yes \\ \hline \hline \end{tabular}
\end{table}
Table 1: ANOVA assumptions assessment.