Distinguishes between alpha activity in the left and right sides of a brain and is used to determine how an ad is affecting the mental processes of the individual viewing it.

The answer is Hemispheric lateralization.  It distinguishes between alpha activity in the left and right sides of a brain and is used to determine how an ad is affecting the mental processes of the individual viewing it. It is the distinction between functions of the right and left hemispheres of the brain. If one hemisphere is more heavily involved in a specific function, it is often referred to as being dominant.