Would you see a gorilla walking through a group of basketball players who were passing balls back and forth? Not if your attention was focused on counting the number of passes made between players, say cognitive scientists. In a now well-known study on “inattentional blindness,” roughly one-half of participants failed to see the woman in a gorilla suit who stopped in the middle of the basketball players, thumped her chest, and then walked away. How can half of the subjects miss the gorilla? According to the study’s authors, Christopher Chabris and Daniel Simons ( http://www.theinvisiblegorilla.com ), this perceptual error results when we focus our attention on a particular aspect of our visual world. When our attention is focused, we tend not to notice unexpected…