NEW YORK —
When inattentional blindness (sometimes referred to as attentional blindness) strikes, our focus on one particular element in a scene or situation or problem causes the other elements to literally disappear. Images that hit our retina are not then processed by our brain but instead dissolve into the who-knows-where, so that we have no conscious experience of having ever been exposed to them to begin with. The phenomenon was made famous by Daniel Simons and Christopher Chabris: In their provocative study, students repeatedly failed to see a person in a gorilla suit who walked onto a basketball court midgame, pounded his chest, and walked off. But the phenomenon actually dates to research conducted by Ulric Neisser, the father of cognitive psychology, in the 1960s and 1970s.
One evening, Neisser noticed that when he looked out the window at twilight, he had the ability to see either the twilight or the reflection of the room on the glass. Focusing on the one made the other vanish. No matter what he did, he couldn't pay active attention to both. He termed this phenomenon "selective looking" and went on to study its effects in study after study of competing attentional demands. Show a person two superimposed videos, and he fails to notice when card players suddenly stop their game, stand up and start shaking hands — or fails to realize that someone spoke to him in one ear while he's been listening to a conversation with the other. In a real-world illustration of the innate inability to split attention in any meaningful way, a road construction crew once paved over a dead deer in the road. They simply did not see it, so busy were they ensuring that their assignment was properly carried out.
Inattentional blindness, more than anything else, illustrates the limitations of our attentional abilities. Try as we might, we can never see both twilight and reflection. We can't ever multitask the way we think we can. Each time we try, either the room or the world outside it will disappear from conscious processing. That's why Holmes is so careful about where and when he deploys that famed keenness of observation. Were he to spread himself too thin — imagine modern-day Holmes, be it Benedict Cumberbatch or Jonny Lee Miller, pulling out his cell to check his email as he walks down the street and has a conversation at the same time, something you'll never see either of these current incarnations actually doing — he'd be unable to deploy his observation as he otherwise would. Enter the email, exit the Baker Street steps — and then some.