Note: This is an excerpt from an article for The Box Move publication that draws on a few major strands of science utilized in artistic mediums such as film or literature.
First written about in Life, the Universe and Everything by Douglas Adams, “an SEP is something we can't see, or don't see, or our brain doesn't let us see, because we think that it's somebody else's problem.... The brain just edits it out, it's like a blind spot. If you look at it directly you won't see it unless you know precisely what it is. Your only hope is to catch it by surprise out of the corner of your eye…. It relies on people's natural predisposition not to see anything they don't want to, weren't expecting, or can't explain.”
Most of us have seen that video of people in white and black t-shirts passing basketballs to each other while a man in a gorilla suit walks to the centre of the screen, thumps his chest, walks off screen, and for most of us, goes unnoticed because we were busy counting how many times the white t-shirt team passed the basketball. That video is pretty representative of how most of us perceive the world. Human beings have developed an ability to pick out the most significant aspects of any scene that we encounter and focus on them only. So while we might think that we’re taking a scene in, chances are that we wouldn’t notice if more than half of it is changed. This ability is important since it lets us concentrate, and keeps us from sensory overload. In fact, most people who have autism are susceptible to sensory overload because, among other reasons, they are not very good at setting up a SEP field.
In another experiment done by Christopher Chabris and Daniel Simons, the guys behind The Invisible Gorilla experiment, the subjects walk up to a counter and the first experimenter hands them a consent form to sign. After they’ve signed the form, the experimenter takes the form and ducks behind the counter to put it away. At the same time a second experimenter, a distinctly different looking man, stands up and hands the subject a packet of information related to the experiment and sends them on. 75% of the subjects did not notice that the person who handed them the packet is different from the person who handed them the consent form.
What makes some people notice the difference and some not? According to Simons, “We really don’t have an idea what separates the people who don’t from the people who do. It might be that there are individual differences – that some people are better able to detect these sorts of changes, but it is also possible that it’s just a coincidence. That the people who noticed it just happened to be focusing on a feature that changed.” That, in other words, they were looking directly at an SEP and knew precisely what it was.
Change blindness and selective attention, aren’t the only examples of SEPs. If you quickly flick your eyes right or left to focus on some object, chances are that you were blind between now and focusing on that object. Not only does your brain make you go blind when you flick your eyes back and forth, but it also actively suppresses these blind moments so that you never notice them. This is also why you don’t feel queasy when flicking your eyes right and left, but might feel queasy or dizzy when you’re shown a video made by a camera doing the same.