Type "the quick brown fox jumps over the lazy dog" a few times and you'll probably see at least one letter on screen you didn't expect.
That's when your conscious brain says, "Oops!"
But it turns out an unconscious part of your brain already knows you screwed up, say researchers from Vanderbilt University. They offer evidence for this in a study just out in the journal Science.
The researchers had skilled typists type words that appeared on screen and then report whether they'd made a mistake.
What the typists didn't know was they were working at computers programmed to mess with their minds.
Sometimes the computer would insert an error into a correctly typed word. Other times it would correct a typing mistake, so the word on screen appeared correct.
People in the experiment usually took responsibility for any mistake that appeared on screen, whether or not they'd caused it. And if the computer fixed a mistake, they generally believed they'd typed the word correctly.
But their fingers told a different story.
When typists hit the wrong key, their fingers slowed down, even if the computer fixed the error. But typing speed didn't change when they typed the word correctly, even if the computer introduced an error.
"The hands know when the hands make an error, even when the mind does not," psychologist Gordon Logan, the study's lead author, explains in a statement. He talks about the study in this Vanderbilt video:
Another experiment showed that the mind was unreliable even when typists were told what the computer was doing to them. Once they knew what was going on, they were much better at catching inserted errors, but still tended to take credit when the computer fixed a mistake.
The study shows that the brain has at least two separate systems for detecting errors we make. One involves looking at the result of our actions. The other monitors something we're doing in real time.
These dual systems mean that "people can compensate for their mistakes even when they are not aware of their errors," Logan says.
Copyright 2010 National Public Radio.