Nature reveals that sometimes our mouths really do move faster than our brains:
But some researchers think that speech is not entirely planned, and that people know what they are saying in part through hearing themselves speak.
So cognitive scientist Andreas Lind and his colleagues at Lund University in Sweden wanted to see what would happen if someone said one word, but heard themselves saying another. “If we use auditory feedback to compare what we say with a well-specified intention, then any mismatch should be quickly detected,” he says. “But if the feedback is instead a powerful factor in a dynamic, interpretative process, then the manipulation could go undetected.”
In Lind’s experiment, participants took a Stroop test — in which a person is shown, for example, the word ‘red’ printed in blue and is asked to name the colour of the type (in this case, blue). During the test, participants heard their responses through headphones. The responses were recorded so that Lind could occasionally play back the wrong word, giving participants auditory feedback of their own voice saying something different from what they had just said.
When the voice-activated software got the timing just right — so that the wrong word began within 5–20 milliseconds of the participant starting to speak — the change went undetected more than two-thirds of the time. And in 85% of undetected substitutions, the participant accepted that they had said the wrong word, indicating that speakers listen to their own voices to help specify the meaning of what they are saying.