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When you are about to cross a street, and you’re looking to make sure no cars are coming, your experience feels, in a word, rich. You are seeing, all in the same moment, the sky, the road, the cars, the traffic lights, pedestrians—all of it.
So it can come as a shock to hear perceptual psychologists saying that, actually, we are only seeing a high level of detail in a tiny part of our visual field—about the size of your thumbnail held at arm’s length. The rest is lacking in detail and color. The reason we experience all that detail, then, isn’t because we are really perceiving it from the world, but rather because our mind is “filling in” those other areas with what we expect to be there. The idea that we’re actually seeing this big, rich world, is an illusion.
Psychologists think this because repeated studies have demonstrated a phenomenon they have come to call change blindness: When you show people two slightly different pictures one after the other, they can see even small changes pretty easily. But introduce a slight pause between one viewing and the next, by showing just a blank white image, and suddenly they can’t. In this “flickering paradigm,” they need to look carefully around the picture, searching for what has changed. Take a look, for example, at these two images, and see how long it takes you to notice what’s changed.
Did you notice how the two photos differ?* If it takes several seconds to identify what’s changed (some subjects stare at the alternating images for over a minute), the reasoning goes, you must not be as aware of the whole image as you think. But a new pre-peer review study by Michael Cohen, a psychologist at MIT who studies how perception works in the brain, challenges this interpretation. He and his colleagues from Amherst College suggest in their paper that we are aware of much more perceptual information than psychologists have traditionally thought.
To test this idea, the researchers decided to see if familiarizing subjects with an image first would improve their ability to recognize changes to it. This had never been done before in change-blindness studies, they say.
We are aware of much more perceptual information than psychologists thought.
In Cohen’s experiment, subjects looked at sets of flickering images like the ones above, which alternate between an original and a slightly changed version, but some of the subjects had been familiarized with the scene beforehand. Then they asked the subjects to stare at the center of these test pictures and try to notice whether the periphery of the picture was somehow altered—scrambled, or in black and white, compared to the originals.
Cohen and his colleagues reasoned that if the “filling-in” hypothesis were correct, subjects who were more familiar with the original image would have a harder time recognizing differences—their minds would populate the periphery with what they had already seen. Cohen and his colleagues proposed a different hypothesis that they called the “expansion” hypothesis: that familiarity with a scene would actually allow one to expand one’s perceptual awareness. If the expansion hypothesis were correct, they reasoned, then study subjects who were more familiar with the original image should be better at recognizing changes between one image and the next, not worse.
Their results supported their expansion hypothesis: People were better at detecting changes to familiar stimuli. Over repeated trials, they found that study subjects had a harder time identifying changes in unfamiliar test images than in familiar ones: The changes needed to be more significant.
This is an exciting development, because it suggests that humans are capable of expanding our visual awareness to include larger areas of our visual field than theories of change blindness propose. It also casts doubt on the filling-in hypothesis, which says we use our memory and expectations to flesh out parts of the world we aren’t currently focusing on.
The findings help to explain why our sense that we take in an entire scene when we gaze on it contrasts so much with the filling-in theory. According to Cohen, when people think about how detailed their perception is, they tend to reflect on familiar scenes from their experience—their homes, neighborhoods, or office—or, at least, scenes they’ve looked at for a few seconds. This study suggests that we feel we are aware of a lot more than psychologists were telling us because, in fact, we are! When we know a scene well, we can expand the borders of visual awareness to process more information. Our perceptual experience might be just as rich as it seems. 
*It’s one of the smaller boats in the middle right of the image.
Lead image: Aman Patel1 / Shutterstock
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