Researchers at the University of Kentucky have been looking into the links between social rejection and aggression in a series of experiments involving a total of 190 college students. In one of the experiments 30 people were given a personality test and then bogus feedback about the results. A third of the participants were told their personalities would mean they would probably end up on their own later in life; these were the excluded group. The rest of the participants were either told they would have 'many lasting and meaningful relationships,' or were given no feedback at all. All the participants were then told to read an essay - supposedly by another participant - and rate their impression of the author's actions. They were also told that the authour was a candidate for a research position. Those participants who had been in the excluded group were far more likely to see the authour's actions as hostile and to give them a negative evaluation as suitable for the job. In anther experiment 32 participants were given the same personality test and again some of them were told that they would end up alone. The participants then 'played' a computer game in which they could inflict a blast of white noise on their opponents. Those participants from the excluded group inflicted a higher level of painful noise on their opponents than those participants in the control group.
You can read more about this research at