"Our brains have a similar enough organization that we can use the patterns of activation from my brain to try to decode yours," says Mitchell.
"I think it's the first time anybody's really been able to read the content of the brain activity in a person's brain, find out what the thought is that the activation signals," adds Just. "The brain is doing something systematic-- it's coding thoughts. And this research for the first time breaks a little bit of that code. It can tell how the pattern corresponds to the thought of an object."
Does that mean scientists may eventually be able to read our minds? In theory, eventually, yes, say the researchers. "I think our work presents a noninvasive way of reading peoples' minds as they're thinking of common objects," Just says.
"We're able to have the computer answer a 10-wise multiple choice test," says Mitchell. "That's still a far cry from being able to have the computer determine whatever you're thinking."
"I think we're doing fabulously well for common objects," agrees Just. "I really think there's no common object we couldn't eventually be able to find a representation of.
"We're also looking forward to working on how ideas combine in the brain-- so not just hammer, but hammering a nail, buying a hammer, and so on. So, a lot of the complexity of human thought comes about when you combine ideas. It's not just one element, its putting elements together into prepositions, sentences, structures," Just adds. "We build our ideas out of simple elements, and we haven't yet studied the building."
"But then, beyond that," says Mitchell, "there are words like love and hate, democracy and totalitarianism; those probably have a very different representation in the brain than these concrete objects that we manipulate as people. We don't know how well we'll do at that. We intend to find out-- we're now in the process of setting up some new studies where we will be collecting data on those kinds of words. And then, beyond nouns, there are questions of, well, what about the more complex compositions that we think about as people? You know, 'the monkey flew over the lettuce.' Given a sentence like that, what happens in your brain? Well, we don't know either, but we intend to find out."
Mitchell says that while it's too expensive right now to "read" peoples' thoughts in real-time, speed is not an issue. "The speed of the processing for the computer is probably not going to prevent us from doing this in real-time in the long term. Once the patterns are learned, its actually a fairly efficient operation. The computer can classify an image, given that image, in less than a second."
So, could these techniques lead to new ways to invade our privacy?
Just points out that while MRI imaging is noninvasive-- no wires or implants required-- "It's, you know, I don't know, like a three-ton machine," he laughs. And we're not going to be doing this in shopping malls tomorrow."
Still, they say it's not too soon to start talking about the ethics of these technologies.
In the meantime, they point out, their aims are beneficial-- decoding how our brains represent thoughts could also help study mental disorders like autism and schizophrenia.
"A person with paranoid schizophrenia-- why are they frightened?" asks Just. "What are they concerned about? We might be able to tell what it is that concerns them. When a person with autism doesn't develop sort of conventional friendships or relationships, we can ask how they view the people they interact with, we can see what the representation is like. Is there some element missing? Is there some new element pressent that isn't normally there? "Once you get to the point of analyzing how people think, what they're thinking about, it gives us a tremendous advantage in many kinds of medical issues having to do with brain function."
This research was published online in PLoS One, January 2008, and funded by the W.M. Keck Foundation and the National Science Foundation.