Impact of Speller Size on a Visual P300 Brain-Computer Interface (BCI) System under Two Conditions of Constraint for Eye Movement

Figure 10

Representation of counterbalanced global dimensions to evaluate satisfaction of different interfaces. Rank was considered as a factor, which was multiplied by the subject’s number that classified each dimension in ranks 1, 2, or 3. Each rank was translated in a positive or negative value (rank 1, ±1; rank 2, ±2; and rank 3, ±3). Positive values were assigned to favourite, comfortable, and controllable dimensions. Negative values were attributed to complex, stressful, and tiring dimensions.