There are various ways to scan the brain. One way is to use functional magnetic resonance imaging (fMRI), which measures change in blood oxygenation. Then there's CT scanning, and a process called PET. Then there's MEG, which measures magnetic fields produced by electrical activity in the brain. Then there's NIRS, another technique for measuring blood oxygenation in the brain.
None of these methods give one single bit of direct information about what someone is thinking or perceiving. However, scientists can try an elaborate technique for matching up brain scans taken at a particular time with data about what a person was observing at some particular time, or what a person says he was thinking at a particular time. It doesn't work very well at all, because two person's brains don't look the same way when they are thinking the same thing, or looking at the same thing. Even a single person's brain doesn't look exactly the same way when that person is looking at the same thing or thinking the same thought at two different times.
But there does seem to be a little bit of a tendency for one brain to look a little like another brain when they are observing the same thing or thinking the same thing. So scientists are able to do a little bit of what I may call a parlor trick. The parlor trick consists of analyzing sets of brain scans, and studying what a brain scan tends to look like when a particular thought is being thought, or a particular thing has being observed. Scientists can use that analysis to make a very weak limited-scope prediction about a person's thought or observations.
For example, when a person thinks about (or observes) something burning in a fire, his brain scan might tend to look a little different from the way it would look if he were thinking of (or observing) someone relaxing in an ocean. So given a set of brain readings, a scientist or a computer might be able to say something like, “It is 20% more likely that he is thinking about relaxing in an ocean than that he is thinking about someone burning in a fire.”
Should we call this type of thing “mind reading”? We should not. A proper term for it is brain scan correlation analysis. But such a term does not attract press attention or investors, so people doing such brain scan correlation analysis might resort to hype, and call it “mind reading” instead. Is there much use that we can foresee for brain scan correlation analysis? Not really. It's probably a dead end. It's basically a kind of parlor trick or stunt, good for attracting a few headlines, but not much else.
In my local library there are many Chinese books I can't read. I might create a new technique for trying to understand Chinese. I might take pictures of the covers of the Chinese books, and run these images through a computer program that correlates certain pictures on the book cover with Chinese words on the book covers. I could probably get a few results I could brag about using such a technique, which might attract some press attention, with headlines about a new computer program that can read Chinese. But such a technique would really be a parlor trick and a dead end. I would never be able to take it much farther, and never be able to really understand Chinese by using such a technique. Such a technique would be similar to using our current type of brain scans to try to read minds.
The items being read in brain scanning are like cloudy blobs, which severely limits the amount of usable information that can be derived from them. If you consider that the same person will have a different set of cloudy blobs when thinking the same thing at two different times (which would differ from the set of cloudy blobs that some other person would produce), it is hard to foresee much use that could be made of such analytics. One application you can think of is creating some kind of lie detector that would work from analyzing brain scans (because the cloudy blobs might look different when someone is lying). But such an approach would probably not be any more accurate than the existing technology of a polygraph.
The cloudy blobs of brain scans
The headline in the story I have cited (referring to “the man who records and stores your thoughts, dreams and memories”) is utterly misleading. What is being recorded is the brain scans of people while they are having thoughts, dreams, or recollections, not the thoughts, dreams, and recollections themselves. The story implies that such storage may be useful because a science of some later age may be able to analyze the cloudy blobs of brain scans more accurately, so that they can figure out memories, thoughts, and dreams from studying these cloudy blobs. There is no reason to be hopeful that any such thing will ever happen. It seems like something along the lines of saying, “Freeze yourself at death, and science will be able to figure out how to revive your body.” We might be able to figure out exactly how thoughts and memories are stored in the brain, but that would require science vastly more advanced than the crude indirect techniques of brain scanning correlation analysis.
When will we actually have technology for reading minds? My guess is sometime between 50 years from now and never. Contrary to the hyped claims of modern would-be technological mind readers, we are simply nowhere near to understanding the mystery of how the brain stores memories and how it produces thoughts. Our knowledge of the matter is so limited that we are not even sure whether the brain is the sole agent involved in storing memory and producing thoughts. We might one day unravel such a mystery after many decades of additional study. Or we might never figure it out.