Change Blindness

This post is based on a book by Stefan Van Der Stigchel titled “How Attention Works: Finding Your Way in a World Full of Distraction.” Change blindness is the failure to spot a major change because something draws one’s attention away from the spot where the change is taking place. Inaccurate eyewitness accounts are often at the root of wrongful convictions, and these are sometimes caused by change blindness. Experiments have shown that test subjects often wrongly identify a person as a thief after seeing a video of a burglary simply because that person happened to appear in the clip. Consider this scenario: you see person 1 walk into a store and disappear behind a stack of boxes. When person 2 appears from behind the books and steals something the shop, Person 1 is identified as a thief.

There is an experiment regarding change blindness that has been recorded and you might already have seen it. In this experiment test subjects are asked to go to a counter and pick up a form. The person behind the counter bends down to get the form and disappears from view for a moment. Then a different person stands up in their place and hands the form to the test subject. Seventy-five% of the test subjects failed to notice the switch. Dr. Van Der Stigchel writes, “So don’t feel too bad the next time your sweetheart walks into the room and says to you, ‘Well, What do you think?’ and you have absolutely no idea which change in his or her appearance is being referred to.” HM’s advance is to respond, “You look great!” in these situations.

Dr. Van Der Stigchel writes that other change blindness rules appear to apply to moviemaking. Changes are less noticeable when they occur simultaneously with a major visual event, such as an explosion, just like a white screen that when shown very briefly can prevent test participants from noticing differences between two seemingly identical images.

Another trick of moviemakers is to use the actor’s direction of view. So when an actor is looking at a relevant object that is located off camera, most viewers will be so busy trying to figure out why the actor is looking at that they will fail to notice when a change occurs in the scene, such as a car driving into the shot. This also makes it easy to switch between two actors who are looking at and talking to each other. Viewers like to follow the direction of view of the person who is the focus of attention, because they assume that theirs is the most interesting point of view.

So we, in addition to radiologists, security scanners and movie directors, have to deal with the fact that we only ever have access to that small part of the world upon which we focus our attention.

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