Pour Guess: The Effect of Glass Shape and an Ice Substitute on Alcohol Pouring and Estimation
BACKGROUND
Research suggests that people are poor at estimating the amount of alcohol they have served themselves. Glass shape, the presence of ice, and alcohol consumption may influence the amount of alcohol people pour and estimate they have poured. The aim of these studies was to examine whether these factors would affect pouring behavior, in the laboratory and in real-world environments.


METHODS
Across 4 studies, 1 laboratory study and 3 conducted during public engagement events, we tested the effect of glass shape (straight sided highball and tumbler glasses) and, using an ice substitute (whiskey stones), the effect of ice on pouring and estimating a self-defined typical drink. We also assessed the association between alcohol consumption and pouring accuracy.


RESULTS
Overall, participants consistently overestimated their typical serving of alcohol, and poured more than 1 U.K. unit when pouring into an empty glass. Findings demonstrate no credible effect of glass shape or ice substitute on alcohol unit estimation or the amount of a typical serving. However, while alcohol consumption was not related to accuracy, the presence of an ice substitute improved accuracy when pouring a single U.K. unit.


CONCLUSIONS
Given that participants overestimated the amount of alcohol in their typical alcoholic drink, self-report measures of alcohol consumption may be overstating the amount of alcohol individuals consume. Additionally, the presence of ice may improve accuracy when pouring standard servings (U.K. units) of alcohol. Therefore, self-report measures may be improved if the presence of ice is considered.