In a more recent study, psychologists from New York University asked students to estimate the distance between their own position and a full bottle of water on the table at which they were sitting. Beforehand, they fed some of the students a diet of pretzels to make them thirsty. The thirsty students judged the bottle to be closer than the other students did. Another study revealed that hills appear steeper to us than they actually are, and that this tendency is exaggerated when the observer is old, unhealthy, or wearing a backpack.
Excerpt from: Born Liars: Why We Can’t Live Without Deceit by Ian Leslie