Are you a glass half full or a glass half empty person? When it comes to dieting, your answer could change how many calories you drink, according to a study published this month in PLOS ONE. Food psychologists have previously found that people drink less and feel more satisfied when they use a tall, skinny glass rather than a short, wide one, because the human brain perceives height more readily than width. Now, researchers suggest a more nuanced reality: The difference also has to do with where you focus your attention when you pour that drink. When the scientists asked people to pour an amount of lemonade that they deemed equivalent to a shot into a glass, the participants poured less into a skinny glass and more into a wide one of the same volume, as expected. But when the team asked the participants to leave a fixed amount of space at the top of the glass, the participants poured more lemonade into the skinny glass, because the same visual bias tricked them to overestimate the amount of space left unfilled in the skinny glass. So if you are on diet, remember to view the glass half full when you use a slender glass.