Why you really should avoid upsetting the big, drunk guy

There are some obvious practical reasons why you might want to avoid provoking the big, drunk guy in the bar. After all, he's bigger than you. However, according to a new study, there's another more psychological reason to be wary - heavier men are, on average, more likely to be aggressive when drunk than are lighter men. Nathan DeWall and colleagues say their finding is consistent with evolutionary theory and research on embodied cognition.

Over five hundred women (average weight 149 lb) and men (average weight 183 lb), aged 21 to 35, consumed either an alcoholic beverage or a placebo drink before taking part in a reaction time contest. The winner of each round had the opportunity to inflict an electric shock on their opponent. Their choices of how strong and long a shock to inflict was the measure of aggression. Unbeknown to the participants, their opponent was fictitious and the game was fixed so that they won fifty per cent of the rounds.

The key finding was that among the male participants only, alcohol interacted with body weight to predict aggression. That is, heavier men who had an alcoholic drink tended to be more aggressive than those who had an alcohol-free placebo drink. By contrast, having an alcoholic vs. placebo drink made little difference to the aggression of lighter men.

Another way of looking at the results was that, among men who had the alcoholic drink, those who were heavier tended to be more aggressive. For the female participants, their weight bore no relation to their aggressiveness. These same findings were replicated in a second study with a further 327 men and women.

It makes sense in terms of evolutionary theory that bigger men should be more prone to aggression, the researchers said, because 'they're more able than weaker men to inflict costs on others in conflict situations.' The same isn't true for women because even those who are larger will usually be smaller and weaker than potential male adversaries.

An association between weight and aggression is also predicted by embodied cognition, the researchers said. This is the idea that the way we think about abstract concepts is rooted in physical metaphors. One example is that we think about importance in terms of weight, thus leading heavier people to feel more important and entitled to special treatment.

Consistent with both these theoretical arguments, past research has indeed found that physical size is related to aggression. However, DeWall's team said their new study is the first to show that weight is a predictor of alcohol-induced increases in aggression. 'It seems that alcohol reduced the inhibition for heavy men to "throw their weight around" and intimidate others by behaving aggressively,' they said.
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DeWall, C., Bushman, B., Giancola, P., & Webster, G. (2010). The big, the bad, and the boozed-up: Weight moderates the effect of alcohol on aggression. Journal of Experimental Social Psychology, 46 (4), 619-623 DOI: 10.1016/j.jesp.2010.02.008