The Simon effect in a discrete sequence production task: Key-specific stimuli cannot be ignored due to attentional capture. Willem B. Verwey12, David L. Wright2 & Rob H.J. Van der Lubbe13 1 Department of Cognitive Psychology and Ergonomics University of Twente Enschede, the Netherlands 2 Human Performance Laboratories Department of Health and Kinesiology Texas A&M University, College Station TX, USA 3 Laboratory of Vision Science and Optometry Faculty of Physics Adam Mickiewicz University, Poznań, Poland Abstract Two experiments were carried out to examine whether practicing a key sequence skill eventually leads to a disregard of the key-specific stimuli as suggested by sequence learning models, or continue to be relied upon as suggested by visual search models. The experiments involved participants practicing two discrete keying sequences by repeatedly reacting to two series of seven letter stimuli. A Simon effect was used as index for stimulus use and was induced by displaying each letter at a location that did or did not correspond with the required response location. Experiment 1 demonstrated that stimulus display continues to attract attention in that the Simon effect was observed for each sequence element, remained quite stable across practice, and did not differ for familiar and unfamiliar sequences. Experiment 2 showed that the Simon effect remained present even with meaningless stimuli that were often harmful. These findings imply that as long as stimuli attract visual attention, they will be processed when executing even highly practiced keying sequences.