# The Effect of Task Complexity on Time Estimation in the Virtual Reality Environment: An EEG Study
## 4 Discussion and Conclusions  
To the best of our knowledge, this study is the first to investigate how time estimation is influenced by task complexity in the VRE. The results of this study revealed three major findings that answer the three questions raised. First, we found that the participants made greater time estimation errors as the task complexity in the VRE increased. Second, in the VRE, the relative beta-band power of EEG was greater for the low task-complexity condition than it was for the high task-complexity condition. Third, we found a negative relationship between time estimation error and relative beta-band power and a positive relationship between time estimation error and mental workload. We explored the impact of task complexity on time estimation in a new task setting, i.e., the VRE. In addition to considering the participants' behavioral and subjective responses, we employed EEG to capture the participants' physiological responses in real-time. The composite of behavioral, physiological, and subjective responses enabled us to overcome the limitations of the self-reported questionnaire of NASA-TLX that is available only after  
Figure 5: Interaction plot with NASA-TLX scores (task complexity x block sequence). Error bars denote 95% confidence intervals. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Variables** & **Coefficients** & \(p\)**-Value** \\ \hline Absolute time estimation error and relative beta-band power at Cz & \(-0.25\) & \(0.01\)* \\ Absolute time estimation error and relative beta-band power at Fz & \(-0.16\) & \(0.11\) \\ Absolute time estimation error and relative beta-band power at Pz & \(-0.17\) & \(0.08\) \\ Absolute time estimation error and NASA-TLX score & \(0.55\) & \(<\)0.001 *** \\ \hline \hline \end{tabular} \({}^{*}p<0.05\), *** \(p<0.001\).  
\end{table} 
Table 3: Correlation coefficients between dependent variables. the completion of tasks and may produce self-reported biases. Our findings in the VRE provided new evidence of the direction of the relationship between the beta-band power of EEG and task complexity. Our finding that the absolute time estimation error was negatively influenced by task complexity in the VRE substantiates the attentional resource allocation theory [67, 68]. Based on this theory, estimating time and conducting cognitive tasks both require attentional resources, of which each person has only a limited capacity. In line with the structuralist point of view [21, 22], this study provided a smaller number of elements to be completed during the low-complexity task and a greater number of elements to be completed during the high-complexity task. As a result, the participants needed to allocate greater attention to the high-complexity task and paid less attention to the process of time estimation, leading to less accurate time estimations than seen during the low-complexity task [15, 67, 69]. We also observed the effect of block sequences on the absolute time estimation error, demonstrating that task repetition significantly improved the accuracy of time estimation results. We note that the practice trial was designed to familiarize participants with the VR environment, task procedure, and device usage with the HMD and VR controllers. The screening survey showed that 38% of participants did not have VR experience. If we had not included the practice trial, the participants likely would have made many task errors due to task misunderstanding and their lack of familiarity with the VR system. These errors would have been reflected in the time estimation. As we designed the experiment to investigate the effect of task complexity only on time estimation, the practice trial was necessary. While the practice trial minimized the impact of previous VR experience, we found an effect of task repetition on the absolute time estimation error. Without the practice trial, we would have expected the effects of block sequences to increase dramatically.