Change Blindness

03.11.2018 |

Episode #2 of the course Most brilliant social psychology experiments by John Robin


Welcome back to more social psychology experiments.

Today, we’re going to talk about change itself.

Take a moment right now to ask yourself how aware you are of everything.

This sentence you’re reading, for example.

What are you aware of?

The way the paragraphs join together or the periods at the end of each sentence telling you that you finished a complete sentence?

What about the image that’s been blinking on and off the whole time you’ve been reading this?

Just kidding!

But today’s experiment actually covers scenarios where indeed, test subjects have been observing one thing, and researchers who designed the experiment made an image flash quickly on and off, and the test subjects were completely oblivious to it.

This effect is known as change blindness, and you’ll soon see that missing things like blinking images is just the beginning of showing how blind we really are to what we see.


Our Great Filter, aka the Brain

When your attention is on, it’s on, and that usually includes only a fine selection of things. Early film editors noticed that continuity errors involving changes to set backgrounds were often not noticed by the audience, while changes relating to the direct action were more likely to be detected. Many other reports from various phenomena over the last several decades led scientists to suspect that, while many people are good at remembering what they have seen, they are poor at remembering specific details in everything they have seen.

Let’s take a popular experiment, for example. These results were published in Psychonomic Bulletin & Review in 1998, by Dan Simons, PhD, and his assistant, Daniel Levin, PhD.

Fifteen random pedestrians were approached on the campus of Cornell University by one experimenter, who had a map and asked them to give him directions. In each trial, after the experimenter and pedestrian had been talking for about 10-15 seconds, two other experimenters carrying a wooden door rudely passed between them.

At this point, the first experimenter (asking for directions) grabbed one side of the door and the experimenter who had originally been carrying that side of the door stayed behind. The two swapped places! The new experimenter kept the map and the pedestrian kept giving directions.

The new experimenter looked significantly different from the original one and had a distinctively different voice.

The shocking results? Nearly 50% of the pedestrians failed to notice at all!

This study demonstrates what is called “change blindness,” and in fact, this effect has now been replicated numerous times in other experiments involving flashing pictures with subtle changes to the background. (See the link at the end of the lesson if you want to try some of them out yourself.)


Saccadic Eye Movements, Our Ever-Changing Change

The current theory explaining change blindness is that when our eyes are focused in one spot, they undergo period jerking motions. These are called saccadic movements. They are very quick and very slight, only a few degrees of motion several times per second, but nonetheless, this means when we are focused on one thing, our eyes skip a beat very quickly and beyond our awareness.

This means that if something changes in our surroundings when our eyes are in the middle of a saccade, we will not notice it.

Change blindness has serious consequences. For instance, if you are texting and driving, you are likely to notice fewer changes to the background (the view through your windshield). This is actually a documented problem, particularly with motorcycle accidents where drivers were talking on their phone. They reported that they never saw the motorcycle at all—and they were probably right! Unfortunately, though, it’s not an excuse, which is why cell phone use has been banned while driving in most countries.

Your takeaway from today’s lesson is to beware whenever your attention is focused in one spot, especially while driving. Let your eyes drift all around rather than in one spot when the surroundings in front of you are crucial, and you’re less likely to fall into the trap of change blindness.

Tomorrow, we’ll shift our attention from change to patience as we explore another popular experiment: the Marshmallow Test.


Learn Something New Every Day

Get smarter with 10-day courses delivered in easy-to-digest emails every morning. Join over 400,000 lifelong learners today!

Learn more


Recommended video

See change blindness in action by way of three tests you can try on yourself.


Recommended reading

The original paper outlining the change blindness experiment.


Share with friends