College students lack knowledge of standard drink volumes: implications for definitions of risky drinking based on survey data.

BACKGROUND: College students tend to pour single servings of beer and liquor that are larger than commonly used standards. The reasons for this are unknown. Students might overpour because they lack knowledge of standard serving sizes. Alternatively, they might know how much alcohol to pour but simply have difficulty pouring the correct amounts. Misperceptions of standard serving sizes could lead to inaccuracies in self-reported consumption. If this is the case, then the validity of students' responses on alcohol surveys and the definitions of risky drinking that are based on them would be called into question. This study examined how college students define standard drinks, whether their definitions are similar to the definitions commonly used by alcohol researchers and government agencies, and whether their definitions of standard drinks are related to the sizes of the drinks that they pour. The study also examined whether feedback regarding the accuracy of their definitions of standard drinks leads students to alter their self-reported levels of consumption.
METHODS: Students (N = 133) completed an alcohol survey and performed tasks that required them to free-pour a single beer, glass of wine, shot of liquor, or the amount of liquor in a mixed drink. Roughly half of the students received feedback regarding their definitions of standard drinks. All students then were resurveyed about their recent levels of consumption.
RESULTS: With the exception of beer, students incorrectly defined the volumes of standard servings of alcohol, overestimating the appropriate volumes. They also overestimated appropriate volumes when asked to free-pour drinks. Positive relationships existed between students' definitions of standard drinks and the sizes of the drinks that they free-poured. Feedback regarding misperceptions of standard drink volumes led to an increase in levels of self-reported consumption, suggesting that students' original estimates of their alcohol consumption were too low.
CONCLUSIONS: Despite the recent focus on alcohol education and prevention at the college level, college students have not been taught how to define standard drinks accurately. They tend to overstate the appropriate volumes, leading them to overpour drinks and underreport levels of consumption. Self-reported consumption levels are altered by feedback regarding the accuracy of students' definitions of standard drinks. The findings raise important questions about the validity of students' responses on alcohol surveys and the definitions of risky drinking that are based them.