 Measurement of the brain signals using the functional magnetic resonance imaging technique fMRI is safe, and there are no known risks or side effects of this procedure. The participant may, however, find that being placed inside the scanner is unpleasant. Measurement of the brain signals with surface electrodes is also considered safe, and there are no known risks or side effects of this procedure. There may be risks associated with the experiment that are unknown to the investigators. Therefore, the participant are asked to inform the investigators if the participant experiences any health problems during the experiment. If any side effects are discovered by the investigators, the participant will be informed immediately. 