The amount of wine you drink is influenced by the shape of the glass, and whether you are holding the glass when you pour it, a new study suggests.

Study participants were told to pour what they considered to be a normal amount of wine into a glass. When they used a wide glass, they poured about 12 percent more than when they poured into a narrow glass. They poured 12 percent more when they held the glass, compared to when they set it on a table, CBS News reports.

The study also found participants poured 9 percent more white wine into a glass than red wine.

Using narrower wine glasses and not pouring while holding the glass may help modestly reduce the amount of wine a social drinker pours and drinks, the researchers note.

“People have trouble assessing volumes,” co-author Laura Smarandescu of Iowa State said in a news release. “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.”

The findings appear in the journal Substance Use and Misuse.

A study published last year found people tend to drink beer more slowly if it is served in a straight glass instead of a curved one.