The artifactual component of the EEG signal is significantly more informative than brain activity with respect to classification accuracy — consistent across different feature extraction methods and classification pipelines.Artifacts in EEG-Based BCI Therapies: Friend or Foe? · Sensors 22(1):96
When researchers separated artifact components from brain-signal components in EEG recordings, the artifacts — jaw, eye and neck muscle activity — were consistently more predictive of intended movement than the brain signal was.
Movement-related artifacts are not random noise. They contaminate the signal of interest in a predictable way, which makes them more useful to an automated classifier, not less. Most published BCI work does not report whether it controlled for this.
The paper draws the distinction that matters: informative artifacts are a helpful friend in communication applications, and a serious foe when the goal is estimating a physiological brain state. A decoder optimised purely for accuracy will happily select for the clench.
We consider this the single most important fact for anyone entering this field, ourselves included. It is why one of our five public commitments is an artifact control.