Fig. 1.

Demonstration of crowding. While fixating the square on the left, try to identify the middle letter in the triplet below. This is hard. We think that you will agree that, if you had to name it, you would be more likely to call the jumbled middle letter M than I. This is the effect of similarity on errors that we measured in our experiment. Now fixate the square on the right and try to identify the middle fruit in the triplet below. (This fruit demo works best in color.) Once again, we think that you will agree that you would be more likely to call the jumbled middle fruit an apple than a lemon. Actually, it’s a peach. Our experiments used letters, but the effect of similarity on errors applies to any kind of object