Take a look at this quick video. You’ll see a set of six small images, arranged in a circle, for 1 second. Then the screen will go blank for 1 second. Finally, one image will reappear in the place of one of the first six pictures. Your job: indicate whether the final image is the same or different as the image that originally appeared in that same spot.
Click here to view the movie (QuickTime required)
In principle, this should be an easy task, right? Your visual working memory can hold around six items at a time, so it shouldn’t be hard at all to remember if the new picture is the same as the one it replaced. So, is the final picture the same as the one it replaced?
Let’s make this a poll (if you don’t know, just guess):
If we’re very accurate at this task, then one answer (the correct one) should dominate. If we’re not very good at it, answers should be closer to 50-50.
In fact, visual memory is a bit more complicated than that. What constitutes a single item in your memory? Is it a whole face? Or does each portion of the face count as a separate item to be remembered?
In a 2007 study, Kim Curby and Isabel Gauthier found that “experts” seem to have a larger visual working memory in their area of expertise than non-experts. (Nearly all humans are experts at recognizing faces, unless the faces are upside-down). But a team led by Miranda Scolari wasn’t convinced. Maybe the distinction between expert and non-expert isn’t the size of working memory, but how detailed it is.
Scolari’s team showed sequences like the one in the video to 12 volunteers, but with a few twists. Sometimes the faces were upright, and sometimes upside-down. Cubes and colored ovals were also shown, and sometimes a mixture of faces and cubes were shown.
Half the time, the single item that reappeared was the same as the item it replaced. What the researchers were interested in was accuracy the rest of the time, when the image changed. Here are the results:
The researchers made a simple calculation to estimate the size of working memory based on the responses. Remember, respondents were asked if the new image was the same or different from the image it replaced. If accuracy is 100 percent, then the size of working memory should be at least six. If it’s 50 percent (equal to random chance), that would suggest that working memory size is zero. As you can see, when there was a big change in the items, the apparent size of working memory was roughly four, and there was no significant difference in the type of images viewers saw. But the key distinction was between upright faces and upside-down faces — when a different upright face was substituted for an upright face, or when a different inverted face was substituted for an inverted face. In this case, memory size for upright faces was about 1.7, while it was only 0.5 for inverted faces. This difference was statistically significant.
The researchers say this means that experts do not have a larger working memory capacity than non-experts. Instead, their memory is more detailed. If experts really had a larger capacity, then they should be more accurate when the faces shift from upright to cube versus inverted to cube. They’re not, even though they could spot a different upright face three times more often than a different inverted face. So experts remember more details, just not more different items.
How did you do on our little example? Did you notice that a different face was substituted? Our task was a little easier than the researchers’ task, because our faces have a few extra features that make them easier to identify — eyeglasses, different lighting, and so on. In the original study, these things were held constant.
M. SCOLARI, E. K. VOGEL, E. AWH (2008). Perceptual expertise enhances the resolution but not the number of representations in working memory Psychonomic Bulletin & Review, 15 (1), 215-222 DOI: 10.3758/PBR.15.1.215