Leave it to a vision researcher to make you feel like Mr. Magoo.

When Jeremy Wolfe of Harvard Medical School, speaking last week at a symposium devoted to the crossover theme of Art and Neuroscience, wanted to illustrate how the brain sees the world and how often it fumbles the job, he naturally turned to a great work of art. He flashed a slide of Ellsworth Kelly’s “Study for Colors for a Large Wall” on the screen, and the audience couldn’t help but perk to attention. The checkerboard painting of 64 black, white and colored squares was so whimsically subtle, so poised and propulsive. We drank it in greedily, we scanned every part of it, we loved it, we owned it, and, whoops, time for a test.

Dr. Wolfe flashed another slide of the image, this time with one of the squares highlighted. Was the highlighted square the same color as the original, he asked the audience, or had he altered it? Um, different. No, wait, the same, definitely the same. That square could not now be nor ever have been anything but swimming-pool blue ... could it? The slides flashed by. How about this mustard square here, or that denim one there, or this pink, or that black? We in the audience were at sea and flailed for a strategy. By the end of the series only one thing was clear: We had gazed on Ellsworth Kelly’s masterpiece, but we hadn’t really seen it at all.

The phenomenon that Dr. Wolfe’s Pop Art quiz exemplified is known as change blindness: the frequent inability of our visual system to detect alterations to something staring us straight in the face. The changes needn’t be as modest as a switching of paint chips. At the same meeting, held at the Italian Academy for Advanced Studies in America at Columbia University, the audience failed to notice entire stories disappearing from buildings, or the fact that one poor chicken in a field of dancing cartoon hens had suddenly exploded. In an interview, Dr. Wolfe also recalled a series of experiments in which pedestrians giving directions to a Cornell researcher posing as a lost tourist didn’t notice when, midway through the exchange, the sham tourist was replaced by another person altogether.

Beyond its entertainment value, symposium participants made clear, change blindness is a salient piece in the larger puzzle of visual attentiveness. What is the difference between seeing a scene casually and automatically, as in, you’re at the window and you glance outside at the same old streetscape and nothing registers, versus the focused seeing you’d do if you glanced outside and noticed a sign in the window of your favorite restaurant, and oh no, it’s going out of business because, let’s face it, you always have that Typhoid Mary effect on things. In both cases the same sensory information, the same photonic stream from the external world, is falling on the retinal tissue of your eyes, but the information is processed very differently from one eyeful to the next. What is that difference? At what stage in the complex circuitry of sight do attentiveness and awareness arise, and what happens to other objects in the visual field once a particular object has been designated worthy of a further despairing stare?