He gave people some decisions to make, and asked people to record the time when they decided them. He showed that there was a blip in the brain 550 milliseconds before a person was aware of deciding.
So he figured that blip, er, signal, was the real decision, occurring in some non-conscious way, and that the conscious mind became aware of the decision a teeny bit later and took credit for it.
This sort of fits the Freudian model. The id decides, the ego makes up a reason for the id's dark doings.
But now... some other people ran some new experiments, which question whether that initial blip is really a secret decision or just the brain gearing up to decide.
"We argue that what looks like a pre-conscious decision process may not in fact reflect a decision at all. It only looks that way because of the nature of spontaneous brain activity."There's many a slip
and maybe a blip
twixt the cup and the lip.