If you are trying to cut down on the amount of wine you drink, choose a narrow glass, the experts say. And in this case, the experts are researchers, not bartenders.
Drinking from a wide glass or pouring the wine while you hold the glass both might get you a heavier-handed pour, researchers from Iowa State and Cornell universities said.
Unlike a bottle of beer or a shot of spirits, a glass of wine is rarely an exact measure. The scientists set out to test some of the conditions that might affect the pour.
"If you want to pour and drink less wine, stick to the narrow wine glasses and only pour if your glass is on the table or counter and not in your hand -- in either case, you'll pour about 9 percent to 12 percent less," said co-author Brian Wansink, director of the Food and Brand Lab at Cornell.
We're not so accurate when we try to determine volume, said Laura Smarandescu, another co-author and an assistant professor of marketing at Iowa State.
Participants in the study -- 73 students and staff who drank at least one glass of wine in a given week -- were asked to pour what they considered a normal glass of wine; the National Institute on Alcohol Abuse and Alcoholism says that's 5 ounces.
If they were pouring into a wide glass, they poured about 12 percent more than if they poured into a narrow wine glass. The same was true when people held a glass, rather than pouring into a glass on the table. The researchers tried other conditions too. People poured 9 percent more white wine into a glass than red -- because of the contrast of color. Food and other things on the table had less effect, the researchers wrote.
Conditions make it easy to drink more than intended, said another co-author, Douglas Walker, an assistant professor of marketing at Iowa State. Their research was published this week in the journal Substance Use and Misuse.
If a person thinks about how much wine he drinks based on the number of glasses, that could be a problem, Walker said. "One person's two is totally different than another person's two."
It's important to become aware of portions -- just as people have for food, Wansink says. Participants were asked about the conditions after the pouring; the researchers found they were generally accurate about which conditions had influenced them.
"Increasing awareness of pouring biases is a step toward limiting alcohol intake for improved health outcomes and preventing alcohol-related problems," the authors wrote.