Drunk people are more impatient and less generous

Understanding the effects of alcohol on our behaviour is important for policy. Do people make more risky decisions when under the influence? Are they more impulsive? Are they more, or less, affected by systematic biases? Answering these questions would help with designing appropriate harm-minimising policies, or at least better assessing the costs and benefits of such policies.

But assessing the impacts of alcohol is also hard, and not helped by garbage research like this. In contrast, a paper last year (pdf) by Luca Corazzini (University of Padua), Antonio Filippin (University of Milan), and Paolo Vanin (University of Bologna) takes a much more robust approach involving lab experiments, different from the traditional observational or field experimental approaches.

Why is it important to find a robust approach? The authors explain:

First, empirical studies of alcohol intoxication based on field data, whether collected from directly observed or from self-reported behavior, typically suffer from self-selection into drinking... Any correlation between blood alcohol concentration and certain behavioral traits may reflect a true causal effect, but could also stem from different propensity to drink alcohol by individuals with those traits.

Second, and relatedly, individuals usually choose at the same time whether, when, where, with whom and how much to drink alcoholic beverages. This means that it is usually hard to disentangle the effects of alcohol from those of the context in which drinking takes place.

Third, the behavioral effects of alcohol intoxication are partly pharmacological and partly triggered by a psychological reaction to the subjective perception of being under the influence of alcohol. Disentangling the two effects requires independent variations of actual and perceived blood alcohol concentration (with implied relevant misperceptions).

In other words, people who drink may be systematically different from those who don't drink, the drinking context matters, and people may behave differently not because of the alcohol itself, but because of how they think they should be behaving under the influence of alcohol.

The paper uses a neat experimental design to get around these problems. They had three experimental groups: (1) received no alcohol and was never told the experiment had anything to do with alcohol; (2) drank no alcohol before the experiment and didn't know whether they had been given alcohol; (3) drank alcohol before the experiment  but didn't know whether they had been given alcohol. Comparing the first and second group gives an indication of the placebo effect of alcohol on behaviour, while comparing the second and third groups gives an indication of the pure pharmacological effect of alcohol on behaviour. They then ran their subjects through a battery of different lab experiments to identify their risk tolerance, impatience, and pro-social behaviour.

What they found was interesting:

Concerning risk preferences, after controlling for optimism, the willingness to pay and other subjective controls, we only detect a marginal positive effect of alcohol intoxication on risk aversion for female subjects.

On the contrary, we find a strong pharmacological effect of alcohol consumption on time preferences: it makes subjects more impatient. The pure impact of alcohol consumption on time preferences remain substantially large even after taking into account its interplay with subjects’ risk attitude. In this respect, net of the pharmacological effect of alcohol intoxication and in line with previous studies, we detect a negative and significant relationship between impatience and risk aversion.

Finally, concerning altruism, our results suggest that alcohol makes subjects more selfish, as we observe a negative and significant relationship between alcohol intoxication and donations to NGOs.

Now, their results might be sensitive to some selection bias, in that the participants in the second and third groups knew that the experiment had something to do with alcohol (which was in the advertisement for participants), whereas those in the first group did not. The no-alcohol group was slightly older and had a much higher proportion of women. Which makes the results on risk aversion a little shaky. The sample size was a little small too - an opportunity for replication beckons (though I suspect your institutional review board would take some convincing).

What do the results tell us (other than that drunk people are more impatient and less generous)? The authors suggest that "alcohol intoxication makes decisions more determined by emotions and less by deliberation", which should not be a surprise to any of us, and provides good reason for policy to place some moderate restrictions on alcohol availability.

[HT: Steve Tucker]