Scarcity: Why Having Too Little Means So Much

by Sendhil Mullainathan

An early study tested this idea by giving subjects a simple enough task: push a button when you see a red dot on the screen. Sometimes, just before the dot appeared, another picture would flash on the screen. For nondieters, this picture had no effect on whether people saw the dot. For dieters, in contrast, something interesting happened. They were less likely to see the red dot if they had just seen a picture of food. Flashing a picture of a cake, for example, reduced dieters’ chance of seeing the red dot immediately afterward: it was as if the cake had blinded them. This happened only with pictures of food; nonfood pictures had no effect. Of course the dieters were not physically blinded; they were just mentally distracted. Psychologists call this an attentional blink. The food picture, now gone, had made them mentally blink. When the dot appeared, their minds were elsewhere, still thinking about the food. All of this happened in a fraction of a second, too quick to control. Too quick to even be aware of. The title of the study says it best: “All I Saw Was the Cake.”