How to measure post-error slowing: The case of pre-error speeding

Post-error slowing is one of the most widely employed measures to study cognitive and behavioral consequences of error commission. Several methods have been proposed to quantify the post-error slowing effect, and we discuss two main methods: The traditional method of comparing response times in correct post-error trials to response times of correct trials that follow another correct trial, and a more recent proposal of comparing response times in correct post-error trials to the corresponding correct pre-error trials. Based on thorough re-analyses of two datasets, we argue that the latter method provides an inflated estimate by also capturing the (partially) independent effect of pre-error speeding. We propose two solutions for improving the assessment of human error processing, both of which highlight the importance of distinguishing between initial pre-error speeding and later post-error slowing.