**3. Results**

### **3.1 Study selection**

This review finds 2524 articles after using the TAK searching strategy above. The exact numbers of each database and term can be seen in **Table 5**. After removing the duplication and first reviewing with SC, 549 articles are saved in three plans, and seven more articles are included with two additional searching methods. Sixty-one articles remained after a second review with EC. Three main reasons for high elimination (approximately 90% of the articles) are no gamification, hybrid BCI, and BCI for assessment but not control. After detailed reading with IQC, we finally marked 28 articles. This reduction is due to insufficient reporting data. The whole search process is presented in **Figure 1**


#### **Table 5.**

*The number of the articles found in 3 plans of stage 1.*

**Figure 1.** *The whole process of searching strategy using PRISMA.*

The means of ICQ of 28 articles are 9.3, while the standard deviation is 2.1. These parameters show that the quality of the chosen articles is relatively high, with an average level of 'important' with slight fluctuation.
