Your Body Detects Typos While Your Conscious Mind Ignores Them
Analyzing the typist's keystroke speed, however, revealed something interesting: when the a mistake was made -- even if the researchers automatically corrected it -- the participants' fingers slowed down slightly before moving on to the next letter. The typists never saw the error and were not, at least consciously, aware of the mistake. Yet their fingers slowed instinctively, indicating that the brain actually detects errors on multiple levels.
Though not definitive, the study implies that we have a hierarchical method of error correction -- a "lower" physical system that does the work and a "higher" system that accepts credit and blame. By manipulating the on-screen text, researchers were able to trick the "higher" system. But the "lower" system, which presumably relies on things like muscle memory, indicated that some awareness of a mistake existed. It's either that, or our fingers have minds of their own.