You can’t see two things at the same time. You may think you can, but you can’t. Don’t believe me? If you don’t already know the punchline of the famous Simons & Chabris video above, take a few minutes to do the experiment on yourself. It makes the point much better than I can.
This human exploit is called inattentional blindness. It was first discovered by Ulric Neisser, the father of cognitive psychology. Writing in Slate, Maria Konnikova explains:
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.When watching the Simons & Chabris video, even if you saw the "surprise" that about half of people missed, you may have noticed you couldn't also see the basketball passes well enough to keep count.
So that’s the exploit, and it is powerful. We would expect persuasion practitioners to use it to their advantage all the time. But here’s the thing: Many times they do the opposite. That is, they inadvertently create inattentional blindness that works agains them. Split screens are a prime example.
In advertising, a "split screen" is typically when the screen is split into two frames, but three-frame splits (triptychs) and four-frame splits (quads) are not uncommon. I have a rule: I only use two-frame split screens for comparisons (e.g. before and after shots), and I only use quads to recap scenes the viewer has seen before. Inattentional blindness is the reason. The viewer cannot “see” more than one frame at a time. She must process them in sequence. This works out fine when looking back and forth for a side-by-side comparison. It also works for visually skimming a recap of four, already-processed scenes. It doesn’t work when each frame introduces new material — unless the viewer has a lot of time and a long attention span.
This is my rule for split screens. Others seem ignorant of this best practice. I routinely see commercials with short, multi-frame scenes featuring all new information, which essentially ensures viewers of the commercial will miss something that's (presumably) important. In the case of a quad, the scene becomes downright overwhelming. The viewer has no idea where to look.
So there you have it: A fascinating human exploit to which even the crafty persuaders in my line of work haven’t paid much attention (pun intended). In fact, I can only think of one type of persuader who uses it regularly: magicians. They call it "misdirection," which is actually a great way to describe how this type of blindness occurs. It misdirects our focus.