If you want to understand how different types of alcohol affect learning, ask a goldfish. That's what one Harvard Medical School researcher did in 1969, when he had them swim around in vodka and bourbon.

Goldfish turn out to be an excellent model species for studying the effects of alcohol. That's because their blood alcohol levels rapidly rise to the level of the alcohol mixed into the water inside their fishtank. In as short as six hours, a researcher can accurately assess a fish's level of intoxication in a completely non-invasive way, just by knowing how much alcohol is dissolved into the water. Once the fish is good and drunk, the researcher can then subject it to various tasks to see how it performs while swimming around in its cocktail.

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And so it was in 1969 that Ralph S. Ryback took thirty fish and dumped them either into regular water, a solution that approximated vodka, or a solution that approximated bourbon. Each alcohol solution contained the same amount of ethanol; the difference between then was the amount of "congeners." Congeners are the chemical compounds produced in fermentation other than alcohols, and there are more congeners in drinks like bourbon than in spirits like vodka. Then he made then learn to swim a type of maze common in animal behavior research called a "Y" maze.

The experiment supported the notion that alcohol in general impairs learning, at least in large doses. But what's really interesting was the effect of bourbon compared to the vodka-like solution. Those who splashed about in bourbon had a much harder time:

Finally, this study provides additional objective evidence that there is a difference between the behavioral effect of ethanol with a low congener content (similar to vodka) and bourbon with a high congener content. Subjects at the same ethanol concentration, with a high congener content (bourbon), could not learn even after 2 consecutive days of training while all subjects at the same ethanol concentration with a low congener content, learned the first day of training. This decrease in performance is due to the congener content of the bourbon.

It isn't just relevant to a goldfish who wants to enjoy a night out with his or her buddies. As with all such research, the question is how the insights from work with goldfish can inform our own species. It turns out that ethanol is metabolized before the congeners are, which means that if you're drinking a high-congener beverage, then they build up in your bloodstream even after the ethanol is processed by your body. And that, according to Ryback, could explain why some hangovers are nastier than others:

Then, with the preferential metabolism of ethanol and its disappearance, the accumulated congener alcohols might express themselves in the hangover effect seen in man with congener beverages.

So, college students: choose vodka. At least, if you drink...like a fish.

[Psychopharmacologia]

Header photo: Bubble-eyed goldfish via Angie Torres/Wikimedia Commons.