Motion Induced Blindness

Pilots are taught that the “rules for the road” in the skies are “see and be seen”! From the very beginning, instructors remind students to look before they turn and to continuously scan the sky for other aircraft. Click here for a related article on collision avoidance, and some very interesting photos!

Pilots are always cautioned against “fixating”, or staring at a point in space. Here’s an interesting visual/perceptual illusion to help demonstrate why this can lead to not seeing what you think you’re looking for! It’s also just a fun demonstration through which we can learn a little more about how we humans work.

So, what gives?

First off, credit where credit is due: This demonstration was built by Dr. Michael Bach. Please see his website for many other interesting illusions!

As far as what is going on with your eye, the human body and brain are absolutely fascinating when you consider in how well such a complex organism works. This however, is a great example of how our human organism can fail us.

The brain is able to filter out what it considers useless information. This isn’t to say that the stimuli (in this case the dots) don’t get processed; rather, the stimulus is discarded by the brain as unnecessary. Current scientific thinking is that this is done so that your consciousness won’t be overwhelmed by all sorts of excess perceptions.

OK, so why do the dots disappear and then reappear?

Did you notice that the disappearance of the dots isn’t dependent on the motion of the crosses? So, this illusion really isn’t about “motion” causing “blindness” at all it turns out. Instead, it’s all about your brain filtering out a stimulus. The way your brain “thinks” about something like this is it discards visual information that doesn’t move.

In order for this illusion to work, you must stare at the same spot, not necessarily the center dot though. As long as you relax, and your eyes don’t move, it won’t take long for your brain to decide that the dots don’t need to be brought to your conscious and made into a perception – even if you want them to be seen! However, since it’s very difficult for a person to keep their eyes from moving altogether, when your eyes do finally move, even if imperceptibly to you, a dot or multiple dots will “reappear”.

Why pilots care –

As a pilot, we care because we are on a collision course with another aircraft, its relative position in our field of view will not change. Accordingly, we see that we shouldn’t stare at a fixed point in space because, clearly, it is possible for our brain to filter out an object that isn’t moving in our field of view, and for it to become, essentially, invisible! That’s not entirely likely for it to go on long-term, so for a backup reason, let’s just say, “It’s really cool to ‘see’ how our eyes work!”

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Article by: Terry Keller Jr.