The skin behind the participant's right ear will be the location for another of our reference electrodes. 

​

Swab the skin over the area (the skin over the skull, not over the ear itself).

​

Exfoliate the area, focusing particularly on the 'bone bump' if you can identify such a bump.

 

Given this is a difficult area to obtain a good signal, it may be worthwhile to spend extra time on the exfoliation step.