Nimble-fingered touch-typists catch errors without even noticing them using an unconscious "autopilot", research has shown.
Scientists made the discovery after conducting experiments designed to separate what typists see on the screen and feel with their fingers.
In the first, the researchers secretly used a computer program to insert random false "typo" errors or correct mistakes typists had actually made.
They found typists generally blamed themselves for the errors the program had inserted, and took credit for the corrected errors.
But their fingers told a different story.
Usually, a typist's fingers slow down when a wrong key is hit. This occurred as normal in the experiment, and was unaffected by computer tampering. Fingers slowed after an actual error, but not when a false typo appeared on the screen.
"We all know we do some things on autopilot, from walking to doing familiar tasks like making coffee and, in this study, typing," said Professor Gordon Logan, from Vanderbilt University in Nashville, Tennessee, who led the research.
"What we don't know as scientists is how people are able to control their autopilots. The remarkable thing we found is that these processes are disassociated. The hands know when the hands make an error, even when the mind does not."
The findings are reported today in the journal, Science.
Two additional experiments were devised to probe awareness more deeply.
In one, typists were immediately asked to judge their performance after typing each word.
In the other, they were first tipped off that the computer might insert or correct errors, and then asked to rate their performance.
The outcome of the second experiment was the same as the original. Typists took credit for corrected errors and blame for false errors, while their fingers slowed down for real errors but not false ones.
In the third experiment, typists were fairly accurate in detecting when the computer had inserted an error. However, they still tended to take credit for corrections the computer had made.
As before, their fingers correctly distinguished between real and false errors.
Co-author Matthew Crump, also from Vanderbilt University, said: "This suggests that error detection can occur on a voluntary and involuntary basis.
"An important feature of our research is to show that people can compensate for their mistakes even when they are not aware of their errors."