## 3 Results
### Objective 2: To Determine Cognitive Load Levels (Low, Medium, and High) in the Participating Groups
The variance inflation (VIF) values--which quantifies the intensity of multicollinearity in a normal least squares regression analysis, and the higher the variance of the estimated regression coefficient, the higher the collinearity--were high for the cognitive load indicators average pupil diameter, saccade direction and average velocity. The presentation type 2 variable (visual-auditory vs. visual) predicted 25.5% (R\({}^{2}\) = 0.255) of the variance with respect to the cognitive load indicators (see Supplementary Materials, Table S2 for the results of the linear regression analysis). In this case, very low values of tolerance were found for the cognitive load indicators fixation point Y, average pupil diameter, saccade direction and average velocity, while there were very high VIF values for the indicators average pupil diameter, saccade direction and peak velocity. Based on these results, which point to collinearity between the variables, a principal component analysis was carried out to group the cognitive load levels into the most relevant load components (see Supplementary Materials, Figure S4). Three principal components were found (see Supplementary Materials, Table S3 for the matrix of principal components). Component 1 comprised the cognitive load indicators mean duration, fixation point X, fixation point Y, average pupil diameter and saccade direction; Component 2 comprised the indicators average velocity and peak velocity; while Component 3 comprised the indicators average GSR and SCR count. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Indictors of**} & \multirow{2}{*}{**Mean**} & \multirow{2}{*}{**SD**} & \multirow{2}{*}{**Minimum**} & \multirow{2}{*}{**Maximum**} & \multicolumn{3}{c}{**Percentiles**} \\ \cline{4-7} \multicolumn{1}{c}{**Cognitive Load**} & & & & & **25** & **50** & **75** \\ \hline
**Group 2** & & & & & & & \\ Mean duration & 153.58 & 35.61 & 93.25 & 237.41 & 136.26 & 153.58 & 173.51 \\ Fixation point X & 1119.89 & 527.97 & 158.17 & 2424.80 & 988.74 & 1119.89 & 1276.17 \\ Fixation point Y & 951.40 & 438.04 & 162.18 & 2023.44 & 849.83 & 951.40 & 1132.69 \\ Average pupil diameter & 6371.50 & 4451.51 & 1132.41 & 19,140.53 & 4432.29 & 6371.50 & 7298.63 \\ Saccade direction & 319,974.78 & 115,718.13 & 41,797.90 & 397,630.64 & 267,580.33 & 319,974.78 & 375,132.14 \\ Average velocity & 229,531.47 & 94,148.06 & 49,784.31 & 382,706.45 & 199,910.41 & 229,531.47 & 266,353.23 \\ Peak velocity & 331,430.91 & 132,544.18 & 64,173.60 & 537,397.30 & 272,005.44 & 331,430.91 & 398,652.17 \\ Saccade amplitude & 7372.37 & 2653.55 & 989.92 & 9646.79 & 5714.81 & 7372.37 & 8285.77 \\ Average GSR & 1.10 & 1.12 & 0.01 & 3.17 & 0.01 & 1.10 & 1.99 \\ SCR count & 8.00 & 11.33 & 0.00 & 38.00 & 0.00 & 8.00 & 16.00 \\ \hline
**Group 3** & & & & & & & \\ Mean duration & 250.43 & 54.94 & 134.61 & 399.59 & 239.68 & 250.43 & 286.75 \\ Fixation point X & 2919.06 & 1260.15 & 1162.95 & 6185.12 & 2068.23 & 2919.06 & 4091.90 \\ Fixation point Y & 2643.52 & 1307.08 & 959.91 & 6157.44 & 2225.84 & 643.52 & 3557.76 \\ Average pupil diameter & 25,055.68 & 7498.00 & 113,585.3 & 40,122.79 & 19,702.44 & 255,055.68 & 29,433.05 \\ Saccade direction & 105,956.02 & 24,936.85 & 51,991.70 & 149,285.16 & 89,490.71 & 105,956.02 & 120,311.50 \\ Average velocity & 84,465.25 & 18,890.28 & 51,017.96 & 121,059.84 & 71,890.70 & 84,465.25 & 97,068.89 \\ Peak velocity & 105,569.23 & 24,746.30 & 64,997.00 & 152,861.24 & 95,035.23 & 105,569.23 & 127,999.83 \\ Saccade amplitude & 2006.29 & 521.67 & 1300.68 & 2952.87 & 1785.50 & 2006.29 & 2645.64 \\ Average GSR & 0.86 & 4.11 & 0.01 & 14.11 & 0.18 & 0.86 & 4.75 \\ SCR count & 11.00 & 12.14 & 0.00 & 39.00 & 6.00 & 11.00 & 24.50 \\ \hline \hline \end{tabular} Note: SD = standard deviation; GSR = galvanic skin response, SCR = skin conductance responses.  
\end{table}