We need to add a bit more to the story. The pickup up truck was stationary, parked in the travel lane while its occupant talked to someone in the front yard of a house on the other side of the road. That is not good practice but, still, the woman on the motorcycle had a quarter mile of clear road in front of her when she came around the curve. What happened?

I think she fell victim to a different form of blindness, a blindness that we all live with all of the time. We are convinced that we see a world full of well-defined, well-understood objects. Here is my computer mouse, there is the paper, the coffee mug, and my lava lamp (really) - all visible in the scene in front of my eyes. What we do not appreciate is that all of these objects may be visible but they are not recognized and understood simultaneously. Your ability to recognize objects is limited to one or a very few at one time. If you could recognize everything at the same time, you might, for instance, be able to read this article and another one at the same time. You can't, even if you make the letters large enough. You can recognize many objects per second - about 20-40 per second for simple objects - but at any given moment, you are only updating your information about one or two of these. The rest of what you "see" is a construction, built up out of what you attended to recently and by some reasonable guesses about the way the world works.

So, our woman comes around the curve and sees the truck ahead of her. She recognizes it and, quite automatically and unconsciously, says to herself ,"I know about pick-up trucks in travel lanes. They are travelling." Her attention moves rapidly from object to object in the scene. We can't know what she was attending to or where she was looking but we don't need to assume that she was not paying attention or driving prudently. Whatever she was doing, when she got her attention back to the truck and discovered that her theory about its motion was wrong, it was too late. The skid marks show that she hit the brakes but by then there was no way to prevent the crash.

Her blindness was two-fold. First, there was the blindness caused by unsuccessful deployment of attention. Second, there was a blindness to the first sort of blindness. Both of these are completely normal aspects of everyday life. We can function with these impairments because, most of the time, the world does not violate our theory. Objects obey the rules. If, while I was not attending, my coffee mug chose to hover six inches above the desk, I might well be unaware of it. Since this does not happen (I assume), I can function with only intermittent updates on its status.

That said, these blindnesses have important effects beyond rare (or maybe not so rare) accidents. For example, there is a literature in radiology on "retrospectively visible" or "retrospectively detectable" cancer. Women get screened for breast cancer and, fortunately, cancers are detected. When a cancer is detected, radiologists routinely check the prior exam to see what that location looked like a year ago. Unfortunately, at rates that are higher than we would like, when you look at This Spot in last year's image, you can see that the cancer was there. It is retrospectively visible. Why was it missed? Probably not because the radiologist was negligent last year. More likely, the radiologist was blind in the double sense that the motorcyclist seems to have been blind. The cancer was right in front of the radiologist's eyes but she did not see it because her attention was not correctly directed to that spot. Moreover, if we grant that the radiologist was conscientious, we would guess that she thought she had looked everywhere she needed to look and was, thus, blind to her own blindness.

There is an obvious difference between the attentional blindnesses that I am describing here and the pathological blindness that we think about when we think about "research ... against the main causes of blindness". However, attentional blindnesses are ubiquitous. We are all blind in this sense and the consequences of this blindness are significant; accidents of many varieties, missed information, failures of eyewitnesses, the list goes on. Of course, the NEI should work to eradicate pathological blindness. It should also work to ameliorate attentional blindness. We can't eliminate it. It comes with the system but if we understood, we could build safeguards that would decrease the chances of missing a cancer or driving into the back of a truck on a clear, straight stretch of road.