My drunkenness means you did it deliberately

With our brains gently soaked in alcohol we're generally more sociable and relaxed - it's a sedative after all. So why do drunk people seem so prone to aggravation and argument? One reason, say Laurent Bègue and colleagues, is that alcohol exacerbates the 'intentionality bias', our natural tendency to assume that other people intended their actions. So when that guy jolts you at the bar and you're drunk, you're more likely to think he did it on purpose.

Bègue's team recruited 92 men (aged 20 to 46) to take part in what they were told was a taste-testing study. They were given three glasses to taste, each containing a cocktail of grapefruit and grenadine cordial, mint and lemon concentrate. For half the participants, the drinks also contained alcohol - approximately the same amount found in five to six shots of vodka. To control for expectancy effects, half the participants with the alcoholic drinks and half the non-alcohol participants were told the drinks were alcoholic. Next, the participants spent 20 to 30 minutes on filler tasks, in keeping with the cover story that this was a taste-test study, and to allow the alcohol to kick-in. Finally and most importantly, the participants read 50 sentences about various actions (e.g. 'He deleted the email') and gave their verdict on whether the actions were intentional or not.

The intoxicated and sober men alike said that obviously intentionally actions (e.g. 'she looked for her keys') were intentional, and that blatantly unintentional actions (e.g. 'she caught a cold') were unintentional. But crucially, when it came to more ambiguous actions, like the email deletion example, the intoxicated men were significantly more likely (43 per cent) than the sober men (36 per cent) to say the action was intentional. Whether participants were told they'd had alcohol or not made no difference.

Why should alcohol have this effect? Bègue's team think that it takes cognitive effort and control to overcome the intentionality bias, especially so as to take in all the information necessary to consider alternative explanations. Alcohol's well-known disinhibitory and myopic (the 'narrowing of attention') effects would clearly undermine these faculties.

'In summary,' the researchers concluded, 'alcohol magnifies the intentionality bias. Napoleon said, "There is no such thing as accident." Our findings suggest that drunk people are more likely to believe Napoleon's statement than are sober people.'
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Begue, L., Bushman, B., Giancola, P., Subra, B., and Rosset, E. (2010). "There Is No Such Thing as an Accident," Especially When People Are Drunk. Personality and Social Psychology Bulletin, 36 (10), 1301-1304 DOI: 10.1177/0146167210383044

How good are we at estimating other people's drunkenness?

Sloshed, trollied, hammered, plastered. We've done a sterling job of inventing words for the inebriated state, but when it comes to judging from their behaviour how much a person has drunk, we could do (a lot) better. That's according to a review of the literature by US psychologist Steve Rubenzer.

We all have our trusted indices for judging other people's drunkenness. Perhaps it's when the eyeballs start floating about as if under the control of a clumsy puppeteer. Or maybe the effusive 'you know I love you' delivered with a trickle of dribble. However, the vast majority of studies find that lay people, police officers and bartenders are in fact hopeless at distinguishing a drunk person from a sober one, at least at moderate levels of intoxication. To take just one example, after watching drunk and sober people being interviewed and negotiating a stair case, bartenders rated them as slightly, moderately or very drunk with an accuracy of just 25 per cent.

It's a similar story when participants are equipped with more structured means of detecting drunkenness. One 1958 study, for example, found no relation between doctors' assessments of people's intoxication (based on pulse rate, general appearance, gait and mental status) and the subsequent performance of those people on a driving course.

Rubenzer also looked at the evidence for specific indicators of intoxication. Alcohol causes reddening of the eyes, the literature shows, but the association between intoxication level and onset or amount of redness is unreliable. Another indicator is smell. The more a person has drunk, the more likely that their breath will be judged by observers to smell of alcohol. However, this indicator is hampered by the lack of a scientific explanation (alcohol has no odour), not to mention the risk of contamination by food smells. Speech slowing and slurring is another sign of intoxication but people are only modestly accurate at using this as a measure. Predictably enough, impaired walking, the last of the specific indicators, tends to increase the more a person has drunk but it only becomes reliable at very high intoxication levels.

The review finishes by looking at established 'sobriety tests': Nystagmus (jerky eye movements when following a moving target); the Romberg (whether a person sways or falls when they stand, eyes closed, with their feet together, arms at their sides); the Finger to Nose; the Finger to Finger; Saying the Alphabet; and the Hand Pat (alternating between clapping with the palms and backs of hands). In summary, performance on these tests does tend to decline as alcohol intake increases but the evidence for this at lower levels of intoxication is mixed and false positives (sober people categorised as drunk) are a frequent occurrence.

'...[J]udging low to moderate levels of intoxication in strangers is a difficult task,' Rubenzer concludes. 'A variety of professions that might be expected to show substantial skill assessing intoxication do not. [And] no behavioural or physical sign has emerged that is consistently related to a specific level of blood alcohol concentration level without large variation among individuals, with the possible exception of nystagmus.'
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Rubenzer, S. (2010). Judging intoxication. Behavioral Sciences & the Law DOI: 10.1002/bsl.935

What's the link between left-handedness and drinking behaviour?

Back in the 70's, psychologist Paul Bakan published a short research report in which he noted that among 47 inpatients on an alcoholism ward, 7 were left-handed - more than you'd expect based on the approximate 10-per cent prevalence of left-handedness in the general population. Bakan described his observation as 'incidental' but according to Kevin Denny, the idea of an alcoholism-handedness link has proven sticky, with some commentators suggesting the stress of being left-handed in a right-handed world is to blame.

Several studies through the years have attempted to replicate the left-handed-alcoholism link but most have relied on small samples and any way the results have been inconsistent. Denny's contribution is an examination of data from the SHARE survey involving over 25,000 people from 12 countries. Left-handers aren't more prone to risky drinking, Denny finds, but on average they do drink more often.

Denny made his finding after categorising survey participants based on their self-reports as either heavy drinkers (those who drink 'almost everyday' or '5 or 6 days a week') or light drinkers (less than once a month or not at all for last six months). There was no evidence that handedness was related to excessive drinking, but left-handers were significantly less likely to be in the light drinker category than right-handers, suggesting that, on average, a left-hander is more likely than a right-hander to drink at moderate levels.

'There is no evidence that handedness predicts risky drinking,' Denny wrote. 'Hence, the results do not support the idea that excess drinking may be a consequence either of atypical lateralisation of the brain or due to the social stresses that arise from left-handers being a minority group.'

Denny acknowledges his study has limitations - all participants in the SHARE survey are over 50, so it's possible his findings don't generalise to younger people. Related to this, it's possible that some heavy-drinking left-handers died before the age of 50, although their numbers are likely to be small. Another potential shortcoming is that some participants categorised as non-drinkers may have been problem-drinkers in recovery.
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Denny, K. (2010). Handedness and drinking behaviour. British Journal of Health Psychology DOI: 10.1348/135910710X515705

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