An effective way for a hBCI to combine all the control channels is to merge their individual decisions – i.e., the estimation of the user's intent – by weighting the contribution of each modality. These weights reflect the reliability of the channel, or confidence/certainty the system has regarding its output. The weights can be estimated from supervision signals such as mental states [e.g., fatigue, error potentials (ErrPs)] and physiological parameters (e.g., muscular fatigue). Another source to derive the weights is to analyze the performance of the individual channels in achieving the task at hand (e.g., stability over time).