Alcohol / Addiction / Illegal Drugs

Feeling fine after one drink? Your brain’s not

If, like me, you enjoy the occasional glass of wine in the evening, you probably don’t feel as though your judgment or alertness is impaired after this one drink. But according to a new study, it is.
a beer on a bar in a pub
Researchers find that just one drink can interfere with decision-making.

Yep, that’s right. Researchers say that we don’t need to guzzle an entire bottle of vino for our cognition to suffer; just a single alcoholic drink has the power to mess with our minds — we’re just not aware of it.

These somewhat disappointing findings are the result of a study by researchers from San Diego State University (SDSU) in California, which they recently published in the journal PLOS One.

The study involved 18 healthy social drinkers, who all took part in a computer-based task that was designed to measure their cognitive control during distractions.

The task measured their reaction time and accuracy when asked to press a button in order match colored squares on a screen, all while being distracted by bogus squares — which the research team calls “flankers.”

The experiment took place under two conditions: after drinking one alcoholic cocktail, and after drinking orange juice (which acted as the placebo).

During the task, the participants sat in a magnetoencephalography scanner. This measured their brain waves, or electrical brain activity, as they attempted to color-match the squares.

More specifically, the scientists measured the subjects’ beta and theta waves. Beta waves play a role in movement control, while theta waves are involved in making decisions.

Drinking impairs decision-making

So, how does a single drink affect our brain waves and overall cognition? Well, the study found that drinking doesn’t appear to affect our beta waves. When it comes to theta waves, however, it’s a different story.

After drinking just one cocktail, study subjects showed a reduction in theta wave frequency: they fell to almost half the frequency of those who drank the orange juice.

In the task itself, the cocktail was found to reduce subjects’ color-matching accuracy by 5 percent, although their reaction times were unaffected by alcohol.

The researchers say that their findings suggest that even a single alcoholic drink can impair our ability to make decisions, though we’re not aware of it. Importantly, because our motor control appears unaffected by alcohol, we’re likely to proceed with certain physical actions, under the illusion that we’re making the right choice.

In terms of how these results might relate to day-to-day activities, driving is the first thing that comes to mind.

“When driving,” notes study co-author Lauren Beaton, an SDSU psychology graduate, “we usually operate on auto-pilot, going through the motions automatically and without much conscious thought.”

“However,” she continues, “occasionally we have to quickly react to stimuli, such as when a car cuts you off. You must be able to override automaticity and use cognitive control to safely navigate the situation. But when drivers are intoxicated,” she adds, “they are less successful at making these quick changes.”

Since the study only included a small number of subjects, it’s hard to make solid conclusions about the effects of alcohol on decision-making.

Still, those of you who deem it safe to drive after “just one drink” might want to think about hailing a taxi, instead.

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