Session 1 Sentence 1 Session 2 Sentence 2a Sentence 2b Acc (%) Char/min Acc (%) Char/min Acc (%) Char/min ITR 4.59 4.64 4.51 4.35 4.26 4.15 3.55 3.51 3.51 3.28 3.16 3.00 3.20 2.79 2.72 2.02 1.47 0.58 0.27 0.00 0.00 2.84 3.75 95.9 85.1 86.5 97.0 91.3 92.7 89.8 88.3 81.7 78.0 93.4 75.3 77.8 57.9 73.4 x x x x x x 84.3 86.2 1.26 0.88 0.94 1.30 1.10 1.01 0.96 1.01 0.65 0.61 1.03 0.50 0.92 0.36 0.51 x x x x x x 0.87 0.91 ITR 7.12 5.07 5.45 7.32 6.05 5.96 5.58 5.94 4.45 4.20 6.08 3.68 4.14 0.64 2.72 x x x x x x 4.96 5.27 100.0 88.6 86.5 94.2 97.9 94.3 83.3 96.8 85.1 68.5 83.9 69.3 88.5 x 68.1 x x x x x x 86.1 86.1 1.41 0.88 0.95 1.14 1.35 1.03 0.76 1.38 0.75 0.40 0.74 0.65 1.06 x 0.61 x x x x x x 0.94 0.94 Listen, you are writing! ITR 7.55 5.38 5.68 6.66 7.01 6.05 4.70 7.27 5.47 2.47 4.74 2.32 6.07 x 2.32 x x x x x x 5.26 5.26 Schreuder et al. Table 2 | Performance summary. User Gender Age VPfaz VPfcc VPkw VPfca VPfcd VPfaw VPfar VPfav VPfcb VPfck VPfau VPfcj VPfcg VPfch VPfcm VPfax VPfci VPfat VPfcl VPfce VPfas Session mean In all sessions mean F M F M M M M M M M F F F M M M M F F M F 27 28 57 23 25 40 31 40 21 43 25 23 33 55 51 28 28 25 44 47 29 34.1 33.4 98.4 98.4 97.0 94.7 92.9 91.7 85.6 84.9 84.7 83.2 81.9 80.6 79.5 79.3 78.3 72.1 58.6 54.1 51.7 40.0 37.5 77.4 88.0 0.83 0.84 0.81 0.77 0.77 0.73 0.58 0.59 0.49 0.50 0.50 0.41 0.40 0.46 0.47 0.32 – – – – – 0.59 0.62 Performance measures accuracy (Acc), characters per minute (Char/min), and information transfer rate (ITR) are given for all subjects and all sentences, as well as age and gender. Two means are calculated over each measure. Session mean refers to the mean when considering all available subjects, whereas In all sessions refers to the mean of only those subjects that succeeded in all sentences. The latter is included for cross session comparison. Subjects are sorted according to their accuracy on the ﬁrst session. Missing values are either because a the sentence was not written by the user (x) or because the Char/min could not be calculated (–). The non-linear relation between accuracy and characters per minutes can be explained by the type of errors committed, i.e., on the ﬁrst or second level. FIGURE 3 | Session differences. Session differences in accuracy (A) and char/min (B) are plotted for all subjects. The black line represents the mean of all subjects in a session and the gray line represents the mean of the 14 subjects that succeeded on all three sentences. (A) No signiﬁcant difference was found between sessions in the accuracy. No learning effect was found even when the number of iterations was reduced to four, as represented by the red, dotted line. (B) The char/min for Session 2 was signiﬁcantly better than for Session 1, which is due to early stopping and less label vocalization. Some subjects performed higher than the theoretic maximum char/min, indicating a particular beneﬁt from the dynamic stopping mechanism. Points are slightly displaced on the horizontal axis to prevent clutter. Frontiers in Neuroscience | Neuroprosthetics October 2011 | Volume 5 | Article 112 | 6