# Spectral Analysis of Electroencephalographic Data in Serious Games
## 5 Conclusions  
The EEG activity while playing an SG was investigated. We investigated 21 subjects (nine males and 12 females). The methods which use the standard signal processing techniques to evaluate EEG was implemented in the MATLAB programming language. The evaluation methods are based on spectral analysis of EEG. We investigated the change of beta activity in game levels with arising difficulty (Figure 10). We found that beta activity does not depend on the level of difficulty for all examined subjects. Subsequently, we focused on another important indicator--the beta/alpha ratio. The beta/alpha ratio is a trustworthy indicator of brain concentration or relaxation. During the gameplay, the beta/alpha ratio was raised almost in all examined subjects except three individuals (Figure 11). Based on the spectrograms, we found out that the results are very individual across the respondents. Even though the results are very individual, the subjects can be split into three specific groups based on characteristic changes in brain activities. The subjects were divided into three groups by the k-means clustering method (Figure 12). The rise of brain activity in all frequency sub-bands during the gameplay is typical for group 1. A distinct decrease of alpha activity is characteristic for group 2, and a very low or negative increase of beta/alpha ratio is typical for group 3. Future research will focus on increasing the number of subjects involved in an experiment to confirm the hypotheses described in this paper statistically.  
The measured results clearly showed that a SG designed in this way activates beta waves of students solving logic puzzles and increases their brain activation and, consequently, their cognitive abilities. The conclusions of the study can be implemented in the educational process, but also in the creation of SG.  
Based on this study, the teacher can be sure during the teaching process that the beta waves of students are activated and their cognitive activities are increased by including a serious game with logical elements in the lesson.  
In future work, we plan to realize the research that will be focused on measurement and compare of beta waves of respondents. They will be divided into two groups: a control group (using paper and pencil) and experimental group (using a serious game). Both groups will have same conditions and they will solve same tasks focused on logic gates (AND, OR, NOR, XOR, etc.).  
Conceptualization, methodology, and writing--original draft: M.H. and B.B.; Writing--review and editing, methodology, M.H. and M.S.; Visualization, M.H., B.B., M.S., and L.H.; Supervision, L.H. All authors have read and agreed to the published version of the manuscript.  
This current project was funded by the Grant Agency of the Ministry of Education of the Slovak Republic under Contract KEGA 011 UCM-4/2018.  
The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the local Institutional Review Board.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The data presented in this study are available on request from the corresponding author.  
We are grateful to [PERSON] and [PERSON] for the English improvements.  
The authors declare no conflict of interest.