Disrupting Apparent Motion In The Visual Speller Using Di erent Button Shapes

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The BBVEP Visual Speller allows locked-in patients to communicate with the outside world again. One of the biggest problems when using the Visual Speller is that the user may be distracted by anything surrounding the target letter. Such a distraction may be caused by a phenomenon called 'apparent motion'. Apparent motion happens when one perceives a sequence of still images as a moving object. From an evolutionary perspective, apparent motion is a useful feature of the human brain because any moving object could be a predator trying to attack. When using the Visual Speller, however, it could decrease the performance. This thesis considers the di erent ways in which apparent motion may arise and how this relates to the Visual Speller. Another Visual Speller, one with di erent shapes, was tested, as the di erent layout could disrupt the apparent motion patterns. The original Visual Speller was found to perform signi cantly better than the Visual Speller with di erent shapes. There were no signi cant di erences found in the subjective experience of apparent motion between the original Visual Speller and the Visual Speller with di erent shapes. 2
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