Research Article
The Role of Visual Features in Text-Based CAPTCHAs: An fNIRS Study for Usable Security
Table 3
Detected significant changes in mean values (tests of within-subjects effects).
| Method | Type III SS | df | MS | F | | Partial η2 |
| HbO | o1 | Line wave rotation | Sphericity assumed | 1.657 | 4 | 0.414 | 3.892 | 0.006 | 0.170 | o11 | Line wave rotation | Sphericity assumed | 1.410 | 4 | 0.352 | 3.427 | 0.012 | 0.146 | o12 | Line wave rotation | Sphericity assumed | 1.044 | 4 | 0.261 | 2.587 | 0.044 | 0.126 | o13 | Line wave rotation | Sphericity assumed | 1.039 | 4 | 0.260 | 2.554 | 0.046 | 0.118 | o16 | Wave rotation | Sphericity assumed | 0.742 | 2 | 0.371 | 3.686 | 0.034 | 0.156 | Line wave rotation | Sphericity assumed | 1.092 | 4 | 0.273 | 3.176 | 0.018 | 0.137 | o2 | Line wave rotation | Sphericity assumed | 1.203 | 4 | 0.301 | 2.736 | 0.034 | 0.120 | o3 | Line wave rotation | Sphericity assumed | 1.115 | 4 | 0.279 | 2.588 | 0.043 | 0.115 | o4 | Line wave rotation | Sphericity assumed | 1.603 | 4 | 0.401 | 3.730 | 0.008 | 0.172 |
| HbR | o6 | Wave rotation | Sphericity assumed | 0.206 | 2 | 0.103 | 3.712 | 0.034 | 0.171 |
| HbT | o1 | Line wave rotation | Sphericity assumed | 1.665 | 4 | 0.416 | 4.024 | 0.005 | 0.175 | o10 | Line rotation | Sphericity assumed | 2.098 | 2 | 1.049 | 4.180 | 0.023 | 0.180 | o12 | Line wave rotation | Sphericity assumed | 1.156 | 4 | 0.289 | 2.542 | 0.047 | 0.124 | o14 | Line wave rotation | Sphericity assumed | 1.172 | 4 | 0.293 | 2.664 | 0.040 | 0.143 | o16 | Line wave rotation | Sphericity assumed | 1.091 | 4 | 0.273 | 3.185 | 0.018 | 0.137 | o2 | Line wave rotation | Sphericity assumed | 1.150 | 4 | 0.287 | 2.624 | 0.041 | 0.116 | o4 | Line wave rotation | Sphericity assumed | 1.285 | 4 | 0.321 | 2.663 | 0.039 | 0.129 | o8 | Line rotation | Sphericity assumed | 2.027 | 2 | 1.013 | 3.586 | 0.038 | 0.166 |
| Oxy | o1 | Line wave rotation | Sphericity assumed | 1.827 | 4 | 0.457 | 3.425 | 0.013 | 0.153 | o10 | Line wave rotation | Sphericity assumed | 1.517 | 4 | 0.379 | 2.850 | 0.029 | 0.130 | o11 | Line wave rotation | Sphericity assumed | 2.120 | 4 | 0.530 | 3.554 | 0.010 | 0.151 | o13 | Line wave rotation | Sphericity assumed | 1.631 | 4 | 0.408 | 2.533 | 0.047 | 0.118 | o3 | Line wave rotation | Sphericity assumed | 2.029 | 4 | 0.507 | 3.022 | 0.022 | 0.131 | o4 | Line wave rotation | Sphericity assumed | 2.004 | 4 | 0.501 | 4.108 | 0.005 | 0.186 | o9 | Line wave rotation | Sphericity assumed | 1.884 | 4 | 0.471 | 3.464 | 0.012 | 0.148 |
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