Mistakes in skilled performance are often observed to be slower than correct actions. This error-slowing has been associated with cognitive control processes involved in performance monitoring and error detection. A limited literature on skilled actions however, suggests that pre-error actions may also be slower than accurate actions. This contrasts with findings from unskilled, discrete trial tasks, where pre-error performance is usually faster than accurate performance. We tested 3 predictions about error related behavioural changes in continuous typing performance. We asked participants to type 100 sentences without visual feedback. We found 1) pre-error performance was more variable before errors than correct key-presses, 2) error and post-error key-presses were slower than matched correct key-presses and 3) errors were preceded by greater variability in speed compared to matched correct key-presses. Our results suggest that errors are preceded by a behavioural signature which may indicate breakdown of fluid cognition, and that the effects of error detection on performance (error and post error slowing) can be dissociated from breakdown effects (pre-error increase in variability).

Performance errors are associated with robust behavioural and EEG effects. However, there is a debate about the nature of the relationship between these effects and implicit vs. explicit error awareness. Our aim was to study the relationship between error related electrophysiological effects, such as spectral perturbations in fronto-medial theta band oscillations (FMT), and error awareness in typing. Typing has an advantage as an experimental paradigm in that detected errors are quickly and habitually signalled by the participant using backspace, allowing separation of detected from undetected errors without interruption in behaviour. Typing is thought to be controlled hierarchically via inner and outer loops, which rely on different sources for error detection. Touch-typist participants were asked to copy-type 100 sentences as EEG was recorded in the absence of visual feedback. Continuous EEG data were analysed using independent component analysis (ICA). Time-frequency and ERP analyses were applied to emergent independent components. The results show that single-trial FMT parameters and Error Related Negativity (ERN) amplitude predict overt, adaptive post-error actions such as error correction via backspace; and, post-error slowing after errors, reflecting implicit error awareness. In addition, we found that those uncorrected errors which were slowed down the most were also the ones associated with a high level of FMT activity. Our results as a whole show that FMT are related to neural mechanism involved in explicit awareness of errors, and input from inner loop is sufficient for error correction in typing. Public SignificanceWe investigated the patterns of brain activity which precede errors and error-correction during skilled typing. This is interesting because it tests how theories of action and error-monitoring apply in a domain where actions are made extremely rapidly (up to ten keys per second). Electroencephalography (EEG) allows us to identify signature changes which have previously been associated with error-related processes in the brain. We showed that two of these signature patterns, the "error related negativity" (ERN) and "fronto-medial theta band oscillations" (FMT), both predict whether a typist is likely to notice and correct an error they make, as well as predicting how much typing slows down after an uncorrected error. The results support the idea -which has been contested -that the ERN reflects our explicit recognition that we have made a mistake.