Since brainwaves are associated with brain disorders and brain disorders are associated with genetics, it would be worth (albeit dangerous politically?) to investigate the link between brainwaves (and by extension, different cognitive faculties) and ethnicity.
This assumes that brainwaves function the same in everybody and that their measurement means anything more than phrenology.
Also that "brainwaves" have meaning beyond the behavior, brain region, and context in which they're being examined.
Do you base this claim off of any scientific evidence? Measuring schizophrenia based off of gamma oscillations is standard clinical practice.