A study suggests that now we can spot the difference in personalities not only by looking at them but differences can also be spotted in their brains.

The result suggests that he size of certain brain regions is related to people's personalities. For example altruistic people had a bigger posterior cingulated cortex, a brain region thought to be involved in the understanding of others' beliefs.

"One of the things that this shows is we can start to develop theories about how personality is produced by the brain," said study researcher Colin DeYoung, of the University of Minnesota.

Scientists have only recently begun to combine personality research with neuroscience in order to figure out the underlying brain mechanisms responsible for personality differences.