He claims that leftbrainers are functioning at the beta wave level, while rightbrainers are at the alpha wave level. Silva believed that alpha waves are significantly better than beta waves. Actually, alpha waves increase in meditation and under hypnosis, indicating lack of focus or visual stimulation, not some higher brain activity. They are also produced by both sides of the brain. And the evidence is very speculative and tenuous that geniuses and creative artists are primarily functioning at the alpha wave level.
Beta waves are evidence of concentration and heightened mental activity.
If they are too extreme, they can be indicative of stress. But no one in his or her right mind should want to eliminate beta waves, unless you are trying to relax or go to sleep, in which case you would want fewer beta waves and more alpha waves if you want to relax and more delta waves if you want to sleep. This allows people to also use the information stored in the subconscious, consciously. It also connects us with higher intelligence, so that we can get the guidance and help that we need. Despite the fact that the Silva Method is promoted with hyperbole worthy of Fox news promoting the notion that aliens built the pyramids, it has many satisfied customers.