What are some advantages and disadvantages to having an overabundance of grey matter in the brain compared to the average person?

More gray matter is associated with better cognitive function, while decreases in gray matter are associated with Alzheimer's disease and other related dementias. An overabundance of grey matter would infer increased intelligence. Being more intelligent than the average person is generally a great benefit, however, it can hinder your ability to relate to others and that can cause problems.