Experimenters' Influence on Mental-Imagery based Brain-Computer Interface User Training

Abstract Context: Motor Imagery based Brain-Computer Interfaces (MI-BCIs) enable their users to interact with digital technologies, e.g., neuroprosthesis, by performing motor imagery tasks only, e.g., imagining hand movements, while their brain activity is recorded. To control MI-BCIs, users must train to control their brain activity. During such training, experimenters have a fundamental role, e.g., they motivate participants. However, their influence had never been formally assessed for MI-BCI user training. In other fields, e.g., social psychology, experimenters gender was found to influence experimental outcomes, e.g., behavioural or neurophysiological measures. Objective: Our aim was to evaluate if the experimenters gender influenced MI-BCI user training outcomes, i.e., performances and user-experience. Methods: We performed an experiment involving 6 experimenters (3 women) each training 5 women and 5 men (60 participants) to perform right versus left hand MI-BCI tasks over one session. We then studied the training outcomes, i.e., MI-BCI performances and user-experience, according to the experimenters’ and subjects’ gender. Results: A significant interaction between experimenters and participants’ gender was found on the evolution of trial-wise performances. Another interaction was found between participants tension and experimenters gender on the average performances. Conclusion: Experimenters gender could influence MI-BCI performances depending on participants gender and tension. Significance: Experimenters influence on MI-BCI user training outcomes should be better controlled, assessed and reported to further benefit from it while preventing any bias.