## 6 Recognition Results of the Same Gestures and Different Gestures  
Using the aforementioned methods, we investigated the four types of gestures described in the previous section. For each studied gesture, we randomly took two samples from five hand gesture operations. The samples were performed by the same person. We first obtained the recognition results for the same gestures. For each of the four studied gestures, we took the samples at different times as motions \"A\" and \"B\" and compared them with each other to obtain the matching points of the extracted features. Table 1 lists the test results of the matching points. Figure 9a shows that the results of the push motion \"A\" tested against itself yielded 245 matching points and the push motion \"B\" tested against itself yielded 251 matching points. The small yellow circles indicate the matching points. Figure 9b shows that, by using the push motion \"A\" to test the push motion \"B\", we could obtain 189 matching feature points. When we switched the matching sequence, that is, using the push motion \"B\" to the test motion \"A\", we could obtain 179 matching points. The pinch out motion \"A\" tested against itself yielded 210 matching feature points, and the pinch out motion \"B\" tested against itself yielded 240 matching points. Using the pinch out motion \"A\" to test \"B\", we could obtain 165 matching points, and we could obtain 149 matching points by switching the test order. A similar test was also performed for the hand rotation motion. The rotation \"A\" tested against itself yielded 320 matching points, and rotation \"B\" tested against itself yielded 311 matching points. The cross-validation of using rotation \"A\" to test \"B\" yielded 192 matching points and the reverse order yielded 188 matching points. As for the gesture of wrist motion from flexion to extension, the motion \"A\" tested against itself yielded 267 matching points; the motion \"B\" tested against itself yielded 250 matching points. Using motion \"A\" to test \"B\" yielded 156 matching points, and the reverse order yielded 140 matching points. From the above analysis, we observe that a stronger matching occurs at the comparison of each identical feature description for each investigated case. The rotation motion case showed the highest matching number of 320 points, and the pinch out motion case showed the lowest matching number of 210 points. Although the matching points of cross-validation for the same gestures were not as high as those for testing with an identical gesture, they still exhibited the largest value of 192 and the smallest value of 140 for the four investigated gestures. In addition, we observed that the comparison order could affect the matching number of points for the same gesture motions. The differences of cross-validation comparisons were 10, 16, 16, and 4 for push motion, wrist motion from flexion to extension, pitch out, and rotation, respectively. The disparity is approximately one order of magnitude less than the number of matching points, which indicates that the effect of the test order could be reasonably neglected. Subsequently, different gestures were examined. For every two cases of the same gestures discussed above, we tested the other three cases of gestures. We selected some examples to illustrate the matching results. Figure 10a-e shows the results of using the rotation motion \"A\" to test the push motion \"A\", the wrist motion from flexion to extension \"A\" to test the pinch out motion \"A\", the wrist motion from flexion to extension to test the rotation motion \"A\", the pinch out motion \"A\" to test the wrist motion from flexion to extension \"A\", and the push motion \"A\" to test the rotation motion \"A\", respectively. The corresponding numbers of matching points were 30, 37, 25, 26, and 26, respectively. The marked matching points (yellow circle) in Figure 10 indicate much smaller numbers compared with that of the same gestures.