Just by looking at the pattern of firing in your brain, neuroscientists can tell whether you are thinking about moving your hand to the left or to the right. They can tell if you have seen something you didn't even know you saw, and, now it seems, they can tell which mathematical operation you secretly have in mind.
[...] Haynes and colleagues put three men and five women into a functional magnetic resonance imaging (fMRI) scanner, and asked them to decide whether they would add or subtract a set of numbers, and to concentrate on that decision.
After a delay, two numbers appeared on the screen, and the volunteers performed the mental maths they had decided on. They then selected the correct answer from a list, revealing to the researchers which option they had chosen.
To see what was happening while volunteers were privately making their decision to add or subtract, Haynes' team looked at changes in oxygen in the blood across the brain. These data, picked up by the scanner, indicate changes in metabolism and so, in neural activity.
A computer program was then fed all these results, so that it could learn to distinguish the patterns of activity associated with a thought about addition from that for subtraction. When they tested the computer's abilities to predict the correct answer on a fresh set of data, the computer correctly determined what the volunteer was planning to do 75% of the time — quite a lot better than the 50% expected from random chance.
[...] As for the notion of making a really thorough mind-reading machine, distinguishing a thought from just two choices is very different from when you have many options, as is more often the case in real life. "If there were ten options, would our predictions be any better than chance?"
Todd Braver, a neuroscientist at Washington University in St Louis, Missouri, is more excited about the study's implications for understanding when we become conscious of the decisions we make. Haynes agrees: "The next step to take is to see whether we can read thoughts about intention before a person has even become conscious of them themselves."
