Your brain registers more than you think you see, NYU researchers find
A team of scientists has mapped out how the brain processes subliminal images
Your brain is capable of retaining information about things you think you haven't noticed, according to a team of scientists in a study published in the journal Neuron on Wednesday.
"Our results indicate that what is 'invisible' to the naked eye can, in fact, be encoded and briefly stored by our brain," said the study's lead author, Jean-Rémi King, a postdoctoral fellow at New York University's (NYU) department of psychology.
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The findings could help scientists better understand conscious versus subconscious perception, as well as how patients recovering from comas are treated.
Using a type of brain imaging known as magnetoencephalography (MEG), the scientists observed subjects as an image was flashed on a screen for just 17 milliseconds, King told CBC News.
They're guessing right, even though they're claiming not to see it.- Jean-Rémi King, New York University
The images were low-contrast pictures of striped circles rotated at different angles.
Using buttons on a keyboard, the study participants were then tasked with comparing their test images to another image in higher contrast that they were shown for a longer period of time, and determining whether the image was rotated to the left or right.
Subjects were asked to rate the image on a scale from zero ("I did not see anything) to three ("I clearly saw an image on the screen"), said King.
"What we found is that, even when subjects claim not to see the stimulus, they are able to maintain its information. They're guessing right, even though they're claiming not to see it."
Subjects guessed accurately at a rate that was statistically above chance, he said.
Advancing earlier findings
Since the early 1990s, aided by the rise of neural imaging, researchers have tried to compare brain activity that occurs when subjects are shown images to what the subjects report that they've seen, said King.
Those studies have helped establish that the brain can process some information from subliminal images, he said, even if the brain's response is "extremely transient." This has led to a number of theories around visual awareness.
"In this study we tried to push this prediction to see whether it was holding in all conditions," said King. "So we asked subjects to try to maintain a visual item in working memory, even when they claim they don't see the stimulus."
King said his work confirms the results of a study done by David Soto in 2011, and takes the investigation further using brain-scanning technology.
King said that although it was beyond the scope of this study, knowledge of how the brain responds to stimulus could be used down the road to better understand people who are in vegetative states recovering from coma.
"The big question for clinicians and for families is to know whether these patients are not responsive because they are paralyzed, or whether they are fully unaware of the environment," said King.
Understanding this better would help physicians care for, diagnose and determine patients' prognoses.