The nature of error detection as manifested by
the error-related negativity was examined in both a Sternberg
memory search task and a visual search task. Both tasks
were performed in conditions with consistent or varied
stimulus–response mapping and loads of three or six
letters. After subjects were trained extensively in all
conditions, they performed the tasks throughout the night
without sleeping. The data suggest that the effectiveness
of error detection decreases over time because of a decrease
in the quality of perceptual processing. Error detection
also suffers when performance requires more search-related
resources. In both cases, the representation of the correct
response is compromised. These results indicate that error
detection depends on the same perceptual and cognitive
processes that are required for correct performance.