The link between alcohol and aggression is well known. What’s not so clear is just why heavy drinkers get belligerent. What is it about the brain-on-alcohol that makes fighting seem like a good idea “and do all intoxicated people get more aggressive” or “does it depend on the circumstances”? New research by University of Kentucky psychologist Peter Giancola and Michelle Corman addresses these questions.

One theory about alcohol and aggression is that drinking impairs the part of the brain involved in allocating our limited mental resources — specifically attention and working memory. When we can only focus on a fraction of what’s going on around us, the theory holds, drunks narrow their social vision, concentrating myopically on provocative cues and ignoring things that might have a calming or inhibiting effect.

The research tested this idea on a group of young Kentucky men. Some of the men drank three to four cocktails before the experiment, while others drank no alcohol. All group members then competed in a stressful game that required very quick responses. Every time they lost a round, they received a shock varying in intensity. When they won a round they gave their opponent a shock. The idea was to see how alcohol affected the men’s belligerence, as measured by the kinds of shocks they chose to hand out.

In addition, Giancola and Corman also deliberately manipulated some of the volunteers’ cognitive powers. They asked some of the drinkers to simultaneously perform a difficult memory task. The idea was to see if they could distract those who were “under the influence” from their “hostile” situation. If they could tax their limited powers of concentration, perhaps they wouldn’t process the fact that they were recieving shocks.

The results confirmed the researchers predictions: The drinkers who had nothing to distract them, exhibited aggression towards their adversaries. However, the drinkers whose attention was focused elsewhere were actually less aggressive than the non-drinkers. The researchers comment that although this seems counterintuitive at first, it’s really not: the non drinkers were cognitively intact, so they would naturally attend to both provocations and distractions in the room, resulting in some low level of aggression.

It appears that alcohol has the potential to both increase and decrease aggression, depending on where’s one’s attention is focused. The psychologists speculate that working memory is crucial not only to barroom behavior, but to all social behaviour, because it provides the capacity for self-reflection and strategic planning. Activating working memory with salient, non-hostile, and health-promoting thoughts, in effect reduces the “cognitive space” available for inclinations towards violence.

Source: Alcohol and Aggression: A Test of the Attention-Allocation Model. Psychological Science Volume 18 Issue 7 Page 649-655, July 2007

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Adding volume to their claim is the new study “Subjective aggression during alcohol and cannabis intoxication before and after aggression exposure” just published in the journal Psychopharmacology.

“The results in the present study support the hypothesis that acute alcohol intoxication increases feelings of aggression and that acute cannabis intoxication reduces feelings of aggression following aggression exposure,” researchers concluded after extensive human trials.

In the study researchers gave two groups either a placebo or what amounted to a Screwdriver (ethyl alcohol plus orange juice). They gave another group either a pot placebo or actual marijuana vapor from a Volcano Vaporizer bag filled with 13% THC bud.

Then researchers made the test subjects play a money game designed to stimulate aggression or “escape” responses.

“Alcohol increased the number of aggressive responses in the PSAP in the alcohol group, whereas cannabis reduced the number of aggressive responses in the cannabis group. … These findings are generally in line with previous studies that showed alcohol-induced aggression at higher doses. … The cannabis group received a moderate to high cannabis dose which diminished aggressive responses during intoxication, which is in line with previous findings.”