Carnegie Mellon University scientists
are training a computer to decode the human mind.
The scientists explain today in the journal Science
how their computer program can read a person's brain
scan and figure out what noun he or she is thinking.
Their goal is to perfect the program so that it can help
autistic, schizophrenic or paralyzed people.
"Imagine somebody who is completely immobilized, a
quadriplegic, who can't talk," said co-author Marcel
Just, a neuroscientist and director of Carnegie Mellon's
Center for Cognitive Brain Imaging. "They could think a
thought and maybe the machine could figure out what it
The work expands on a separate study the same
scientists published earlier this year showing that
people's brains activate similarly when they think about
the same word.
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In the latest study,
the scientists used functional magnetic resonance
imaging (fMRI) to measure changes in blood flow in the
brain as volunteers thought about 25 verbs, such as
"see," "hear," "taste," "run" and "push."
When given a noun -- such as "celery" -- the computer
program searches for it in a database containing 1
trillion words of text. Once the noun is found, the
program searches for nearby verbs.
The program predicts what it thinks the brain scan
would look like if a person were thinking of that noun
by blending the brain scans from the 25 verbs, giving
more weight to the verbs that occur most frequently with
the noun in the text.
So for celery, such verbs as "eat" and "taste" would
dominate the predicted brain scan, while "ride" wouldn't
When given a brain scan of a noun, the computer
program was 72 percent accurate in picking the word it
was associated with out of a list of 1,001 nouns.
"The bottom line is -- and this is what's really new
here -- nobody had previously even tried to build a
theory or computational model that would predict neural
activity for ... arbitrary words," said co-author and
computer scientist Tom Mitchell, who heads the School of
Computer Science's Machine Learning Department.
Prior to this study, scientists could only figure out
the word a person was thinking if they already had a
brain scan of that word, said John-Dylan Haynes, a
neuroscientist at the Bernstein Center for Computational
Neuroscience in Berlin. He did not participate in the
"This very interesting study now shows a method that
allows one to read out a large number of different
thoughts from brain activity, even with only a few
calibration measurements," Haynes wrote in an e-mail.
Mitchell and Just have been tweaking their computer
model to interpret simple sentences. They've also done
small studies that show the brain scans of a bilingual
person are the same, regardless of which language they
use to think of a noun.
"Possible applications could include brain-computer
interfacing, neuromarketing and even possibly detection
of concealed thoughts for criminal investigations,"
Just said such applications could be feasible but are
still several years away because the fMRI machine is
large and expensive, several computers have to be united
to handle the data and people have to remain very still
for long periods.
"Plus, you can't make somebody think something
consistently," Just said. "All they have to do is think
of something else."