An e-mailer, who seems to know of what he speaks:

As usual I am quite suspicious of any fantastic-sounding “study”. I can make an argument that people who drink that much are typically bar-flies who are usually bantering/arguing with a group of friends, constantly competing to have their voice heard. These types of people MUST have the verbal and thinking skills in order to stand out, lest they be ignored. So the cause/effect may be backwards here.