Table 2.

Variation of the support vector machine classification performance with different features.

Number of features	Added feature	Accuracy (%)	Sensitivity (%)	Specificity (%)
1	Total SLa	79.49	68.42	90.00
2	~b +Mouth_Session 1	84.62	78.95	90.00
3	~ +Wholebody_Session 3	92.31	84.21	100.00
4	~ +Face_Session 3	92.31	84.21	100.00
5	~ +Face_Session 2	92.31	89.47	95.00
6	~ +Eyes_Session 4	92.31	89.47	95.00
7	~ +Face_Session 1	92.31	89.47	95.00
8	~ +SL_Session 2	92.31	89.47	95.00
9	~ +Wholebody_Session 1	89.74	89.47	90.00
10	~ +Face_Session 4	92.31	89.47	95.00
11	~ +Mouth_Session 2	92.31	89.47	95.00
12	~ +Eyes_Session 1	89.74	84.21	95.00
13	~ +Eyes_Session 2	89.74	84.21	95.00
14	~ +Mouth_Session 3	87.18	84.21	90.00
15	~ +SL_Session 3	89.74	84.21	95.00
16	~ +Wholebody_Session 4	89.74	84.21	95.00
17	~ +Mouth_Session 4	87.18	84.21	90.00
18	~ +Eyes_Session 3	84.62	78.95	90.00
19	~ +SL_Session 1	82.05	78.95	85.00
20	~ +SL_Session 4	79.49	78.95	80.00
21	~ +Wholebody_Session 2	76.92	73.68	80.00

^aSL: session length.

^bIn forward feature selection, ~ represents all features in the previous iteration; for example, ~ represents all 6 previously selected features in the 7th iteration.