How Far Off Is Mind-Reading?

By Neuroskeptic | June 28, 2009 9:15 am has a somewhat enthusiastic article about the possibility of using fMRI to “uncover your private thoughts”- Mind-Reading Tech May Not Be Far Off.

Neuroscientists are already able to read some basic thoughts, like whether an individual test subject is looking at a picture of a cat or an image with a specific left or right orientation. They can even read pictures that you’re simply imagining in your mind’s eye. Even leaders in the field are shocked by how far we’ve come in our ability to peer into people’s minds. Will brain scans of the future be able to tell if a person is lying or telling the truth? … While we aren’t there yet, these possibilities have dramatic social, legal and ethical implications.

But what do we mean by “mind-reading”? I guess what most people mean by the term is being able to tell what someone is thinking, being able to “hear” their private thoughts. A stereotypical fictional “telepath” can get inside their targets minds and tell exactly what’s going through them.

Sadly, what most fMRI “mind-reading” experiments have done is rather less impressive. they’ve shown that it’s possible to tell whether someone is thinking about one thing as opposed to a second thing. But only if you already know what both things are, and only if you have already “read” the pattern of neural activity that corresponds to each one.

So, you could scan someone while they are thinking about, say, cats, and then again while they are thinking about dogs. From that, you could work out whether they are thinking about cats or dogs at any given point in time (here’s how). If they were thinking about anything else, you’d have no idea what it was, or worse, you’d think it was either a cat or a dog. A lion, for example, would probably activate many of the same pathways that a cat does.

The great majority of “mind-reading” studies are like this. It’s still pretty cool, but it’s no telepathy. Is there any prospect of true “mind-reading”? In other words, could you read a mental state without knowing what you were looking for in advance?

Maybe. The parts of the brain concerned with visual processing happen to be arranged in a relatively straightforward way,which means that there are predictable relationships between visual stimuli and the areas of the brain that are activated when looking at them. Reports have claimed that it’s possible to infer which picture someone is looking at out of a large set (1) and even to reconstruct the image that someone is looking at based purely on the visual cortex activity (2,3). For a good explanation of the last paper, which attracted a lot of attention, see Neurophilosophy.

Such studies come closer to true “mind-reading”, but thus far the technique only works with vision. Even assuming that the same areas of the brain light up when you’re thinking about something (visual imagery) compared to when you’re looking at it (visual perception), the best this method could achieve would be to tell what picture was in someone’s head at a given time. In ten years it might be possible to put someone in a scanner and tell, straight off the bat, that they were picturing a small white dog. But if you wanted to know what they were thinking about that dog, you’d be out of luck.

To truly read someone’s mind you would need to understand how every brain state relates to every mental state. In other words, you would need to know how the brain allows us to think. At the moment, we really have no ide about that, so true mind-reading remains over the horizon.

Edit: I must be telepathic because I just saw that Mind Hacks covered a new study about mind reading a few hours ago: I know where you are secretly attending! Yet again, it involves the visual cortex.

CATEGORIZED UNDER: fMRI, media, neurofetish
  • Richard

    Yes! Indeed, and this is why MRI evidence used in court is potentially so dangerous (e.g. ) – especially if the jury don't understand how it works or what it's really doing.

  • Phil

    These kinds of claims drive me nuts. It shows a complete lack of understanding of fMRI. It reminds me of the claims for 'neuromarketing' and a role for fMRI in market research

    I personally believe that fMRI is much overused/overrated, even in psych research. Its a fashionable and expensive tool that is often poorly applied in badly designed research projects.

  • David Bradley

    Are these brain states similar from person to person? So if I know what Amy's brain looks like when she's imagining a dog, do I know what Brian's brain looks like when he's imagining a dog?

  • Neuroskeptic

    That's an excellent question.

    Some aspects of neural organization do seem to be shared across individuals. So whenever you think about a face, there will be activity in your fusiform face area, and whenever I think about a face there will be activity in roughly the same place.

    Now on the other hand the particular collections of cells which fire when I think about, say, Michael Jackson's face (insert joke here) will not be the same as yours.

    So we could feasibly put someone in a scanner and know, off the bat, that they were thinking about faces but we'd need to map out their individual brain to know more than that.

    The exception to this however is the visual cortex, some parts of which seem to be organized in a very straightforward way – basically a bit of the brain acts like a screen where activity in different parts corresponds to different areas of the image – if you could decode that you could plausibly tell what someone was looking at without mapping them out first.

    But I don't know what quality image you would get (I suspect it would amount to little more than a vague outline).

  • David Bradley

    Thanks for your response. I imagine this would have large implications for mind-reading. I seem to remember an article about trapped-in syndrome, where a person has no voluntary movement but an active mental life. They stuck these patients into brain scanners and asked them to think about playing tennis, or walking through their home, to see if the patients were able to control their mental function. I gather from what you're saying that the person in the scanner might be thinking about walking around their friends' home or playing basketball, and with the current resolution levels the doctors would never know?

    I'm not sure how much American TV you watch, but there was an episode of House recently that dealt with this: they hooked up a guy (played by Mos Def) to a machine that could read his brain patterns, and the guy was able to control the mouse on a screen to answer basic questions (up for yes, down for no, that sort of thing). Occasionally, House gets it mostly right, is this sort of thing possible? It seems like a general enough movement that it might be possible.

  • David Bradley

    And then, minutes after posting this comment, I find the answer reading Steve Novella's blog. D'oh!



No brain. No gain.

About Neuroskeptic

Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.


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