In a brain-computer interface paper, I found the following paragraph:
Effective assessment of BCI performance requires two levels of evaluation: the user and the system. The user must control the signal features ..."
My question is how can a person control the signal features of his/her brain signal? Does this mean, for example, that a person can give more attention to increase signal to noise ratio for the P300 signal, and be able to look more carefully at the screen that shows flashes in an SSVEP experiment?