The way that this technology works is that you let them look at your brain while think about, say, playing tennis, then playing golf, then playing football. Then, later on, they say, "call to mind one of those three memories we worked with before." And they can tell you which of the three you are remembering.
In the study, Maguire and her colleagues Martin Chadwick, Demis Hassabis, and Nikolaus Weiskopf showed 10 people each three very short films before brain scanning. Each movie featured a different actress and a fairly similar everyday scenario.
The researchers scanned the participants' brains while the participants were asked to recall each of the films. The researchers then ran the imaging data through a computer algorithm designed to identify patterns in the brain activity associated with memories for each of the films.
Finally, they showed that those patterns could be identified to accurately predict which film a given person was thinking about when he or she was scanned.
It's not like they could take someone who hasn't been a part of the study, plug them into the machine, and figure out what they are thinking about. The technique they describe only works with individuals and for specific memories for which they have an established baseline that can be used for comparison.
