Seeing Things That Aren't There? That's Just Your Brain Functioning Normally
David Berreby is the author of "Us and Them: The Science of Identity." He has written about human behavior and other science topics for The New Yorker, The New York Times Magazine, Slate, Smithsonian, The New Republic, Nature, Discover, Vogue and many other publications. He has been a Visiting Scholar at the University of Paris, a Science Writing Fellow at the Marine Biological Laboratory, a resident at Yaddo, and in 2006 was awarded the Erving Goffman Award for Outstanding Scholarship for the first edition of "Us and Them." David can be found on Twitter at @davidberreby and reached by email at david [at] davidberreby [dot] com.
"Pay attention to that alley over there. A gorilla in a clown suit is going to come out of it in a second." If I said that to you, and the ape subsequently appeared, you would (rightly) conclude that I'd helped you see the beast by focussing your attention on the right place at the right time. Suppose, though, that I'd said to look at the alley after the gorilla rushed by. And then you realized, hey, I saw a gorilla over there! That would be weird right? After all, if awareness is a straightforward record of what we've seen, then you either see the gorilla or you miss it. Outside of dreams, there's not supposed to be "miss the gorilla, look where it was, then change the record to say that you saw it." But, this paper suggests, intuition is wrong, and this dreamlike revising is indeed a part of everyday waking perception. In other words, it isn't always seeing a gorilla that makes you focus on the alley. Sometimes, focussing on the alley makes you see the gorilla.
In the study, published last month in the journal Current Biology, Claire Sergent and her colleagues had 18 volunteers look at a computer screen on which were two circles. After a moment, one of the two circles filled with fuzzy parallel lines for a mere 20th of a second. The volunteers then had to say which circle contained the lines and how they were oriented (vertical, horizontal or various kinds of diagonal). People's ability to answer correctly was much enhanced if they had a cue—if the correct circle dimmed a bit just before the lines appeared—thus drawing their attention.
Remarkably, though, people also did better on the task if the relevant circle dimmed about a half second after the lines had appeared. As Sergent et al. write, "this suggests that, contrary to a commonly held assumption, postcueing can influence perception itself."
You might think that this cueing effect was a sort of hallucination—that people could have imagined lines only because, and wherever, they'd seen the circle dim. But Sergent et al. eliminated that possibility by dimming both circles in one set of tests. In this case, people still saw the lines in the place where they had really appeared before the cue. They weren't following the cue alone to imagine something wherever it appeared; rather, the focussing device was leading them to see something that really had appeared—but which was no longer visible when they realized they had seen it.
There has been a lot of research over the years on perceptions that never reach awareness. For example, people whose visual cortex is damaged are unaware of seeing anything, yet they often react to things in their field of vision. Sergent et al.'s study is significant because it's not about these kinds of perceptions outside of consciousness. Instead, it's a demonstration that the mind can edit perceptions before they reach consciousness. Therefore Sergent et al. also had to eliminate the possibility that these results were a kind of blindsight, in which people were giving correct answers without knowing how or what they knew.
To address this, the researchers ran the experiment on another 18 people, and this time, added a measure of their awareness: in addition to saying where the lines were and how they were oriented, volunteers also had to rate how visible they were. There was a certain amount of projection, or "response bias," here, with people reporting better visibility wherever there was a cue (even when no actual lines had appeared). Despite that noise, though, there were "drastic improvements" the reported visibility of lines that had appeared and vanished just before the attention-focussing cues. In other words, post-event cues weren't just causing people to see lines in the right places; those cues were also causing people to know that they'd seen something. Which suggests that the reality you see around you isn't a "raw feed" of data coming from the eyes and visual centers of the brain, but a product that has been edited—and (as Dan Dennett points out here) is still being edited, by "you," even as "you" consume it.
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Sergent, C., Wyart, V., Babo-Rebelo, M., Cohen, L., Naccache, L., & Tallon-Baudry, C. (2013). Cueing Attention after the Stimulus Is Gone Can Retrospectively Trigger Conscious Perception Current Biology, 23 (2), 150-155 DOI: 10.1016/j.cub.2012.11.047
Here's the science of black holes, from supermassive monsters to ones the size of ping-pong balls.
- There's more than one way to make a black hole, says NASA's Michelle Thaller. They're not always formed from dead stars. For example, there are teeny tiny black holes all around us, the result of high-energy cosmic rays slamming into our atmosphere with enough force to cram matter together so densely that no light can escape.
- CERN is trying to create artificial black holes right now, but don't worry, it's not dangerous. Scientists there are attempting to smash two particles together with such intensity that it creates a black hole that would live for just a millionth of a second.
- Thaller uses a brilliant analogy involving a rubber sheet, a marble, and an elephant to explain why different black holes have varying densities. Watch and learn!
- Bonus fact: If the Earth became a black hole, it would be crushed to the size of a ping-pong ball.
Protected animals are feared to be headed for the black market.
In a breakthrough for nuclear fusion research, scientists at China's Experimental Advanced Superconducting Tokamak (EAST) reactor have produced temperatures necessary for nuclear fusion on Earth.
- The EAST reactor was able to heat hydrogen to temperatures exceeding 100 million degrees Celsius.
- Nuclear fusion could someday provide the planet with a virtually limitless supply of clean energy.
- Still, scientists have many other obstacles to pass before fusion technology becomes a viable energy source.
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