Take a look at the following pictures of U.S. dimes. As you can see, they are slightly different from one another — the date is in the incorrect spot on one of them. Can you tell which one is “wrong”?
Let’s make this a poll:
Don’t look at your pocket change before you answer! In case you don’t have a dime handy, I’ll reveal the correct answer later in the post.
Even though most Americans will say they know what U.S. coins look like, a similar study in 1979 found that people can’t remember the basic details of a penny. More recently, change blindness studies have shown that we are very bad at detecting changes in scenes, even those that seemingly take place before our eyes.
But Luke Rosielle and Jeffrey Scaggs point out that change blindness isn’t much of a problem in the real world because things don’t ordinarily disappear or change right in front of our eyes, or in the moment when we glance away. A much more common type of change happens when we’ve been away for a longer period of time. If you leave town for a few weeks, you might be likely to notice that your favorite coffee shop has been repainted. This is the sort of change we may be more likely to notice. Or are we?
Rosielle and Scaggs showed 48 students pictures of their own college campus, and told them that half had been photoshopped to remove or change prominent campus buildings and monuments. The students carefully observed each picture for 20 seconds, then said whether the photo was accurate or modified. After each photo, they rated their familiarity with the scene on a scale of 1 to 10. On average, the students were familiar with 97 percent of the scenes. However, they failed to identify the changes to 81 percent of the photos!
So even though the students said they recognized the scenes, they flopped at actually noticing what had been modified. Why? Rosielle and Scaggs showed the same scenes to 48 new students from the same campus, but this time they were shown the original and altered pictures side-by-side. These students were asked how difficult it would be for others to identify the changes in the pictures. Interestingly, their ratings matched the errors made by the first group of students: they could predict how good other students would be at identifying changes at a rate significantly better than chance. That said, they still weren’t very good at predicting: they thought students would get about half the answers correct, when in fact they missed over 80 percent!
The researchers showed the same pairs of pictures to 48 students from a different school, who had never seen the original college campus. These students were unable to predict how well students from the original campus would do; their predictions bore no relationship to the actual results.
So it seems that while our memories of scenes aren’t as good as we think they are, the memories are indeed better than nothing. The students from the different university tended to rate the larger changes (those occupying the most pixels on the screen) as easier to spot, but the students who actually attended the school recognized other features as more likely to be noticed. This makes some sense — you’d probably be more likely to notice if your favorite coffee shop closed down than if the same thing happened at a larger place you never visit. But it’s striking that even very familiar places don’t actually stick very well in our memories at all.
If this is the case, then we should expect that our readers didn’t do very well on the two polls above. For comparison, here’s an unaltered photo of a dime:
As you can see, dime B had the date in the correct spot. But both dimes were missing a very large feature: the word “LIBERTY” to the left of Roosevelt’s face. Did you notice all these changes? Let us know in the comments.
Rosielle, L., & Scaggs, W. (2008). What if they knocked down the library and nobody noticed? The failure to detect large changes to familiar scenes Memory, 16 (2), 115-124 DOI: 10.1080/09658210701787765