Table 4. Comparison of Classification Accuracy in Different Frequency Bands With and Without Feature Selection Base on Correlation.

Correlation	Without feature selection	With Feature selection
	Mean (S.D.)	Mean (S.D.)	p
Theta	0.47 (0.03)	0.55 (0.02)**	1.26×10−25
Alpha	0.42 (0.03)	0.53 (0.02)**	5.79×10−32
Beta	0.40 (0.02)	NS
Gamma	0.40 (0.02)	NS

Note: NS: No couples of electrodes were selected since there was no main effect among emotional states (i.e. no feature selection was performed);

**Accuracy with feature selection is significant higher than that without feature selection, p<.01.