“You can turn your back on a person, but never turn your back on a drug, especially when it’s waving a razor sharp hunting knife in your eye.” – Hunter S. Thompson
It is widely accepted that alcohol causes aggression. This link is even evident in historical records of ancient Greece in the 4th and 5th centuries.  However, it is also well-documented that alcohol does not always cause aggression. Alcohol may lead the same person to feel happy one day and enraged the next. The reason for these different effects is now better understood and may be the key to preventing alcohol from causing aggression.
For more than 25 years, scientists who study the relation between alcohol and aggression have used Alcohol Myopia Theory (Steele & Josephs, 1990) to interpret their findings. Alcohol Myopia Theory essentially states that alcohol intoxication causes people’s attention to be narrowed. I like to think of attention as a spotlight: Sober people have a very wide spotlight, and thus can perceive a lot of information in their environment – both information that is significant and noticeable as well as information that is much less obvious and easily overlooked. But because drunk people’s “attentional spotlight” is narrowed, they tend to only perceive and consider information that easily captures their attention. This is why alcohol can have so many different effects: Drunk people’s behavior is primarily driven by their attention to these highly salient cues in their environment, and the cues that are most obvious may vary from situation to situation.
What about a conflict situation? When your friend insults you to your face, that insult is unmistakable. But there is likely other relevant information in this situation.  Maybe your friend is under a great deal of stress and their insulting you is out of character. Perhaps you think about the many potential negative consequences of getting into a verbal or, even worse, a physical fight. This information, which could actually help you to hold back from being aggressive, is typically less salient than the overt, verbal insult. 
Sober people are better able to process all of these cues. But, because alcohol narrows the “attentional spotlight," drunk people tend to focus only on the most salient information in their environment – which in a conflict situation tends to be information and cues that provoke aggression. And there we have it: Alcohol causes people to be more aggressive because they focus on aggression-promoting cues.

A Counterintuitive Idea: Can Alcohol Reduce Aggression?

What would happen if we made those cues which inhibit aggression more noticeable? According to Alcohol Myopia Theory, a drunk person should focus predominantly on those inhibitory cues and, as a result, be less aggressive. Increasing the salience of inhibitory information leads us to the somewhat counterintuitive idea that alcohol can actually reduce aggressive behavior.
My colleagues and I have conducted several studies which support this idea. In these studies, male participants drank a dose of alcohol that placed them above the legal limit for driving a car – an average breath alcohol concentration of .09%. Then, they engaged in an aggression task, which was framed as a reaction time competition in which they could also behave aggressively toward another participant. Importantly, while engaged in the aggression task, roughly half of the participants were also told that they could complete a second, unrelated task to earn more money – which we called “the tile game.” Thus, we used the tile game to distract people’s attention away from the aggression task.

In the first study to test this counterintuitive idea that alcohol can actually reduce aggressive behavior (Giancola & Corman, 2007), participants who were intoxicated and in the non-distraction condition showed a very well-established pattern: They were the most aggressive. However, participants who were intoxicated and in the distraction condition were the least aggressive – even less aggressive that sober subjects! Thus, distracting a drunk – but not a sober – person’s attention away from an aggressive interaction led to them to be less aggressive.
A subsequent study (Gallagher & Parrott, 2011) replicated this finding but added a new element. We wanted to test where participants’ attention was actually focused. To do that, we measured participants’ attention toward aggression-related words.  Our findings supported Alcohol Myopia Theory: Drunk and distracted participants showed an attentional bias away from aggressive words, whereas participants in the other groups – namely the alcohol, non-distracted group – showed some attentional bias toward aggressive content.
In a third study (Gallagher & Parrott, 2016), we tested heavy drinking men and replaced the tile game with self-awareness cues in the participants’ testing room. The assumption is that, for most people, increased self-awareness should be linked to prosocial, non-aggressive behavior. So, in the experimental group, participants were in a room with two large mirrors and security cameras that displayed their behavior on a television in real time. Their drinks sat on a coaster that said, “What does my behavior say about me?” Participants in the control group sat in an identical testing room, except that it was devoid of these inhibitory cues.
Once again, we found that when inhibitory cues were noticeable and unavoidable – in this case, cues that increase self-awareness – aggression was reduced among drunk participants. And, of interest, exposure to self-awareness cues only reduced aggression for heavy drinking men who endorsed certain traits that suggest receptivity to self-introspection (Purvis, Gallagher, & Parrott, 2016).

What Does This Mean For Prevention of Alcohol-Facilitated Aggression?

Let’s first agree on the obvious: Alcohol can’t cause aggression if people don’t drink. But the reality is that many people consume alcohol and many people treated for an alcohol use disorder do not achieve sustained abstinence. Thus, one promising approach to reduce alcohol-facilitated aggression is to design interventions that increase the likelihood that drunk people will notice inhibitory cues. What might actual interventions based upon this work look like?
One might envision strategically placed slogans (e.g., in a bar, on a cocktail napkin) that enhance self-awareness or inhibition – such as a slogan like “Drink, Fight, Go to Jail” or “What Happens Tonight Goes on Facebook Tomorrow.” Another idea is to use a non-violence chip akin to the abstinence chips used in Alcoholics Anonymous. If a person always carries that chip and understands its meaning, then its mere presence in a situation, or the feeling of it in one’s pocket, may help to redirect attention toward information that would help a drunk person hold back from being aggressive. Though untested in natural settings, this approach holds promise as a method to shift attention away from provoking cues and ultimately decrease alcohol-related aggression.
^{Dr. Dominic Parrott is a Professor of Psychology at Georgia State University and Executive Secretary for the International Society for Research on Aggression. His research uses laboratory and survey methods to examine risk factors and mechanisms for aggression perpetration, with a particular emphasis on the effects of alcohol on intimate partner violence, aggression toward sexual minorities, and sexual aggression.}