In new research, reported in the current online issue of the journal Social Neuroscience, researchers from the University of Georgia and San Diego State University report for the first time that social exclusion actually causes changes in a person's brain function and can lead to poor decision-making and a diminished learning ability.
I read several years ago of research that found that school bullies were found to be of normal I.Q. when they entered school, but when they were older, they scored below average. Perhaps this new research is at least part of the reason. I suspect that it at least partly due to a dependence on bullying, rather than peaceful interaction, with others, resulting in less exercise of of the intellect. We know that using one's brain results in the growth of connections between brain cells, and possibly in the number of brain cells.