This is the paper mentioned in an earlier post:
Current Biology, Vol 17, 323-328, 20 February 2007
Haynes JD, Sakai K, Rees G, Gilbert S, Frith C, Passingham RE.
Yahoo report: By MARIA CHENG, AP Medical Writer
BERLIN – At a laboratory in Germany, volunteers slide into a donut-shaped MRI machine and perform simple tasks, such as deciding whether to add or subtract two numbers, or choosing which of two buttons to press. They have no inkling that scientists in the next room are trying to read their minds — using a brain scan to figure out their intention before it is turned into action.
In the past, scientists had been able to detect decisions about making physical movements before those movements appeared. But researchers at Berlin’s Bernstein Center for Computational Neuroscience claim they have now, for the first time, identified people’s decisions about how they would later do a high-level mental activity — in this case, adding versus subtracting.
The research, which began in July 2005, has been of limited scope: only 21 people have been tested so far. And the 71 percent accuracy rate is only about 20 percent more successful than random selection.
In one study, participants were told to decide whether to add or subtract two numbers a few seconds before the numbers were flashed on a screen. In the interim, a computer captured images of their brain waves to predict the subject’s decision — with one pattern suggesting addition, and another subtraction.