The taste of beer, without the effects of alcohol, is enough to trigger the urge to drink more, according to a study released Monday.
When given a small amount of beer, the taste triggered a dopamine reaction in the centers of the brain most often associated with addiction and cravings. The findings suggest that just a small sip can lead a drinker--or an alcoholic--to want to drink more.
"Just a little taste is sufficient to increase people's desire to drink," says David Kareken of Indiana University, the study's lead author.
The response was stronger in people with family histories of alcoholism.
Kareken says the result suggests beer might have a Pavlovian Effect on humans.
In Ivan Pavlov's famous experiment, the Russian physiologist discovered "classical conditioning"—a form of learning that suggests that one stimulus can elicit a certain response because of an expected outcome. In his experiment, if a human rang a bell before feeding dogs, the dogs eventually began salivating as a response to the bell.
Kareken says that the taste of beer in drinkers works in much the same way. In his experiment, beer drinkers were given 15 milliliters—an extremely small amount—of their favorite beer over the course of 15 minutes, which enabled them to taste beer without perceptible blood alcohol increases. The taste alone was enough to trigger the release of dopamine—a hormone associated with rewarding activities—in the brain. When given Gatorade, there was no dopamine response. The study did not test nonalcoholic beers, but previous studies have suggested that drinking them could lead to relapse for alcoholics.
"What we showed is you don't need intoxication from alcohol to produce the release of dopamine," Kareken says. "The taste alone is enough."
Previous studies have suggested that the smell of beer can trigger cravings, but Kareken's study was the first to show actual hormonal changes in the brain.
"Given that subjects who had a family history of alcoholism had the strongest dopamine response, the findings suggest that even the taste of beer can provoke the urge to become intoxicated," he says.
A drinker's brain might be conditioned to expect that he'll get drunk if he continues to drink beer, while an inexperienced drinker might not have the same effect, Kareken says.
"When intoxication is unexpected [by the brain], that's when you find the dopamine release from the [alcohol] itself," he says. "As certain sensory cues become associated [with getting drunk], the dopamine release moves away from the reward and happens with the stimulus."
In other words, the taste, not the alcohol, becomes Pavlov's bell for the brain's reward centers, he says.