# Promoting Optimal User Experience through Composite Challenge Tasks
## 8 Discussion and Conclusions  
In this paper, we claim that interactive systems that enforce balanced challenges foster a state of flow and improve performance. A balanced challenge is one in which the mental and motor skills that the user needs to deploy to achieve the task successfully are demanded by the system in similar proportions. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Challenge** & **N** & \(\bar{x}\) & \(\sigma\) & **Error \(\bar{x}\)** \\ \hline BG & 19 & 8.3955 & 0.78433 & 0.17994 \\ NBG & 19 & 7.7759 & 0.97911 & 0.22462 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Mean and deviation standard of the Balanced and Unbalanced challenges. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Leveane’s Test for Equality of**} & \multicolumn{6}{c}{**t-test for Equal Means**} \\  & **Variances** & & & & & & **Lower** & **Upper** \\ \hline  & **F** & **Sig.** & **t** & **df** & **Bilateral Significance** & **Mean Difference** & **Std. Error Difference** & **Confidence Interval** \\ \hline  & & & & & & & & **Lower** & **Upper** \\ \hline
**Equal variances** & & & & & & & & & \\
**assumed** & 1.486 & 0.231 & 2.15 & 36 & 0.038 & 0.62 & 0.29 & 0.4 & 1.2 \\
**Equal variances** & & & & & & & & & \\
**not assumed** & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Student’s \(t\)-test result for Balanced vs Unbalanced challenges. We first presented and tested a methodology to measure the mental and the motor load involved in interactive tasks, and hence to assess whether the challenges in a human-computer interaction task are balanced. Then, we developed a methodology to assess whether balanced challenges do promote a state of flow better than unbalanced ones, and to evaluate whether flow promotes performance better. To test these hypotheses, we developed two interactive systems with tangible interfaces implementing serious games oriented to rehabilitate shoulder injuries: SIBMER and Macoli. Both systems had two versions, one implementing balanced and the other unbalanced challenges. The experiments confirmed that in both systems balanced challenges promote a better state of flow, and in the case of Macoli flow was correlated with high performance. These results suggest that balanced challenges promote flow and flow improves performance. However, in SIBMER the unbalanced version was more complex and attractive than the balanced one, and playing one version of the game first biased playing the other. However, this contrasts strongly with Macoli in which the balanced version is more complex and attractive than the unbalanced one, and playing one version of the game does not influence playing the other. These observations taken together suggest that balanced challenges do promote flow and flow promotes better performance independently of the mental or motor load, and of the complexity and attractiveness of the system. In summary, the experimental study presented in this paper provides support to the hypothesis that HCI systems involving balanced challenges are more likely to induce a state of flow than systems with the same or similar goals that involve simple or unbalanced challenges. These results are very positive and encouraging but need to be corroborated with further systems and experiments in different settings and application domains. A more general approach would be to include an emotional dimension in addition to the physical and the mental, and to explore whether a balance between the three dimensions impact on flow. The present study was also restricted to the user-experience aspect of the systems, and the application to the rehabilitation of actual patients with shoulder injuries is left for further work. Conceptualization and methodology R.C. and L.A.P. ; software, validation, formal analysis, experiments and data collections, R.C. ; writing-original draft preparation, writing-review and editing, R.C. and L.A.P; supervision, L.A.P. R.C. was funded by a CONACyT's doctoral research grant No.