In the latest leap of mind-reading, scientists say they were able to decipher a person's emotions through brain scans.
Patterns of neural activity can give away what people are thinking and feeling, that is, if scientists can make meaning out of brain scans obtained through functional magnetic resonance imaging (fMRI). In past studies, researchers have shown they can determine what number a person is thinking of, predict where people are standing in a virtual reality environment, and even figure out what a person is dreaming about, all by looking at brain scans.
In the new study, researchers at Carnegie Mellon University investigated where anger, disgust, envy, fear, happiness, lust, pride, sadness and shame live in the brain. To guarantee that study participants would be able to reliably and repeatedly conjure up these emotions, 10 method actors were recruited from the school's drama department. [Image Gallery: Slicing Through the Brain]
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"They're really good at putting themselves into these emotional states," study author Karim Kassam said in a video from Carnegie Mellon. The actors were instructed to write scenarios for each emotion, so they could slip into the right sentiment on cue while lying down in an fMRI machine.
By looking at the brain activity of the actors, the researchers found there were neural signatures associated with each emotional state, and that these signatures were shared across individuals.
"Despite manifest differences between people's psychology, different people tend to neurally encode emotions in remarkably similar ways," graduate student and study researcher Amanda Markey said in a statement.
A computer model that learned the brain patterns associated with the actors' self-induced emotions could eventually guess which emotion was being evoked with a high degree of accuracy. The model was most accurate in identifying happiness, and least accurate in pinpointing envy. It usually did not confuse positive and negative emotions, the researchers said.
Lust was rarely mistaken for any other emotion, and lust's pattern of neural activity was not associated with positive or negative emotional signatures, suggesting it could belong to an entirely different class of feeling.
The researchers were concerned that an emotion like anger, when summoned by the actors, would be different from anger spontaneously experienced by the rest of the population. To keep this potential disparity in check, they designed a second experiment in which participants were not asked to invoke any emotion on their own, but instead they were shown images meant to disgust them.
When the actors saw the sickening pictures, the computer model predicted that they were experiencing disgust 60 percent of the time, and listed disgust among its top two predictions 80 percent of the time, the researchers found.
The scientists said they were surprised that the computer could also accurately predict emotion based only on the activation patterns in a subsection of the brain.
"This suggests that emotion signatures aren't limited to specific brain regions, such as the amygdala, but produce characteristic patterns throughout a number of brain regions," said Vladimir Cherkassky, senior research programmer in the psychology department.
The scans could open up new ways to examine emotion in studies without having to rely on self-reporting, a sometimes unreliable method, the scientists said.
"It could be used to assess an individual's emotional response to almost any kind of stimulus, for example, a flag, a brand name or a political candidate," Kassam said in a statement.
The findings were published Wednesday (June 19) in the journal PLOS ONE.
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