Researchers at Iowa State and Cornell universities have discovered how the amount of wine you pour is influenced by a variety of environmental factors and could have serious consequences when it comes to overconsumption of alcohol.

During the study, participants were asked to pour what they thought was a normal drink using different types of glasses in various settings. The results revealed just how easy it really is to overdo it. Participants poured about 12 percent more wine into wide glasses than standard ones. The same was true when pouring while holding the glass rather than pouring while the glass was on a table.

“People have trouble assessing volumes,” said Laura Smarandescu, co-author and assistant professor of marketing at Iowa State. “They tend to focus more on the vertical than the horizontal measures. That’s why people tend to drink less when they drink from a narrow glass, because they think they’re drinking more.”

Researchers tested six environmental factors to understand how each one influenced the amount poured. The contrast between the glass and color of the wine also appeared to make a significant difference. When pouring white wine into a clear glass, participants poured nine percent more than red, which had greater contrast to the glass. The influence of a small or large table was not as strong.

Wine is different from alcoholic drinks that are served in a bottle or measured with a shot glass, making it easy for individuals to overpour. A standard serving of wine is five ounces, according to the National Institute on Alcohol Abuse and Alcoholism. However, Douglas Walker, an assistant professor of marketing at Iowa State and co-author of the study, noted that it is easy to lose track of how many drinks you’ve had, if you are pouring more than you realize.

“If you ask someone how much they drink and they report it in a number of servings, for a self-pour that’s just not telling the whole story. One person’s two is totally different than another person’s two,” Walker said. “Participants in the study were asked to pour the same amount at each setting, but they just couldn’t tell the difference.”

This study was published in the journal Substance Use and Misuse.