## 3 Model Validation
### Results and Discussion
According to [PERSON] and [PERSON] (2016), task switching can occur not only when the task is too difficult but also when the task is perceived to be too easy. Thus, the difference in results at difficulty level 1 could be attributed to the self-interruption caused by perceiving the ongoing task as being too easy. Finally, Figure 9 and Table 6 present the total performance time for the subject data and model data. According to a goodness-of-fit analysis ([PERSON], 1955), the correlation coefficient and RMSE were calculated as r = 0.97 and RMSE = 18.83 for the total performance time. The results indicate that our task-switching model can predict the total performance time at different levels of difficulty and provide a representation of task switching in discretionary multitasking. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Level of Difficulty**} & \multicolumn{2}{c}{**Mean (Standard Deviation)**} \\ \cline{2-3}  & **Subjects** & **Model** \\ \hline Level 1 & 0.417 (0.67) & 0.75 (0.86) \\ Level 2 & 1.08 (0.99) & 1.25 (1.42) \\ Level 3 & 1.17 (0.94) & 1.33 (0.98) \\ Level 4 & 2.0 (1.13) & 2.33 (1.55) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mean of task switching during the execution of a subtask for subjects and model data. Figure 7: Average number of task switching occurrences during the execution of a subtask in the memory game for the subject and model data. In summary, the results in the experiment demonstrate that the cognitive model in this study can provide a relatively accurate representation, in terms of task-switching percent just after the completion of the ongoing subtask, the amount of task-switching during the execution of the ongoing subtask, and performance time depending on the task difficulty level. It exhibits enhanced performance in predicting human behavior in discretionary multitasking environments and demonstrates how ACT-R facilitates accounts of voluntary task switching. However, since the experiment in this study was conducted  
Figure 8: Performance time for a small unit task involving the selection and clicking of a card according to the presence or absence of task switching during the execution of a subtask in the memory game for (**A**) subject data and (**B**) model data. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Mean (Standard Deviation)**} \\ \cline{2-5}
**Level of Difficulty** & \multicolumn{2}{c}{**without Task Switching**} & \multicolumn{2}{c}{**with Task Switching**} \\ \cline{2-5}  & **Subjects** & **Model** & **Subjects** & **Model** \\ \hline Level 1 & 1.2 (0.28) & 1.04 (0.27) & 1.95 (0.23) & 1.25 (0.27) \\ Level 2 & 1.24 (0.37) & 1.37 (0.30) & 1.86 (0.62) & 1.79 (0.32) \\ Level 3 & 1.36 (0.62) & 1.34 (0.32) & 1.93 (0.66) & 1.76 (0.24) \\ Level 4 & 1.99 (0.68) & 2.20 (0.70) & 3.00 (1.08) & 2.75 (0.46) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Performance time (s) in a small unit task for selecting and clicking a card according to the presence or absence of task switching in the memory game for subject and model data. with a somewhat small number of subjects and the conclusions should not be interpreted to statistically represent the general population.