Giancola and Corman wanted to know why drunks are more aggressive.

The prevailing model to explain this effect is what is called the attentional allocation model wherein the alcohol inhibits an individual's ability to focus on a broad range of stimuli -- they become attentionally myopic. This means that when they focus on something that is provocative, they will become super-provoked. When they are focusing on something less provocative, they will become less provoked because they can more successfully ignore the provocative stimuli. It is in essence the horse-blinder theory of aggression.

To test this they got people drunk. If you don't think that is fabulous in itself, then you should read this sentence that appears in the Methods section of the paper:

Subjects in the alcohol condition were administered a dose of 1g/kg of 100% alcohol mixed at a 1:5 ratio with Tropicana orange juice.

Science has now experimentally defined the screwdriver. (Although I would call 1:5 pretty weak sauce...) (Ed. Removed so that people won't think the Editor is an alcoholic and because I realized that they were talking about pure grain alcohol, not something 80 proof.)

Then they compared the ability to arose anger in subjects that were drunk compared to those that were not. How you do this is you use something called the Taylor aggression paradigm wherein the participants can administer shocks to one another. The amount of aggression is measured by the size of the shock delivered.

To look at the relationship between being attentionally myopic and being drunk, the researchers also had some of the drunk participants and some of the controls memorize a sequence of illuminated grid squares. This serves to elevate their attentional load.

The data is below:

As you can see the aggression measured in the control subjects, it is about the same for both conditions. However, when the drunk subjects are not distracted, they are particularly aggressive. When they are distracted, their aggression falls below normal levels.

The experimenters view this as validation of the statement that drunk subjects are more aggressive because their working memory is contracted. The contraction prevents successful behavioral inhibition by crowding out nonhostile cues with hostile cues:

In conclusion, our results indicate that alcohol can both increase and decrease aggression, depending on where one's attention is focused. As already alluded to, the mechanism underlying this myopic effect of alcohol seems to be disruption of working memory (see Finn, 2002). In general terms, working memory involves the ability to encode, maintain, and process and manipulate information (external and internal representations) in the short term. Successful behavioral inhibition and regulation require (a) that one is able to act upon inhibitory representations in working memory and (b) that these inhibitory representations are salient. We propose that working memory helps regulate social behavior by providing the capacity for information processing involved in, for example, hypothesis generation, self-reflection, previewing, outcome evaluation, resistance to distraction, problem solving, abstract reasoning, and strategic planning (i.e., executive functioning). We argue that activating and loading, yet not overloading, working memory with nonprovocative, inhibitory cues can attenuate aggression by allowing behavioral output to be influenced by such cues. In turn, this creates less "cognitive space" to house and process hostile cues. (Emphasis mine.)

I do have a couple little problems with this paper.

1) They are equating attentional load with working memory, but that is a rant for another time. The amount of things you can attend to and your working memory are not necessarily equivalent.

2) This study ignores the possibility that the alcohol limits the complexity of the things your working memory can contain. In this sense the size of the working memory may not be the issue. You just can't think of things more complicated than aggression.

3) You could argue that the increased aggression effect is the result of a broad change in the interpretation of reward -- i.e. aggression becomes more strategically desirable, and that this is present in the distracted drunk case but you can't see it because they are not paying attention to the task.

For those reasons, I would make the claim that the attentional allocation model is not necessarily true.

However, there is one exceedingly useful take home from this work. If your friends get belligerent when they are drunk, distraction works wonders.

Incidentally, this study totally reminds me of that scene in Ghostbusters...

"I'll you what the effect is: it's pissing me off!"

Hat-tip: Eurekalert