The impact of response frequency on spatial stimulus-response correspondence effects

The Simon effect in a discrete sequence production task: Key-specific stimuli cannot be ignored due to attentional capture

Two experiments examined whether practicing discrete key pressing sequences eventually leads to a disregard of the key-specific stimuli, as suggested by sequence learning models, or whether these stimuli continue to be relied upon because the associated luminance increase attracts visuospatial attention. Participants practiced two sequences by reacting to two fixed series of seven letter stimuli, each displayed at a location that did or did not correspond with the required response location. Stimulus use was indicated by a Simon effect in that key presses were slowed when stimulus and key locations did not correspond. Experiment 1 demonstrated that letter stimuli continued to be used as the Simon effect occurred with each sequence element, and this 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 even harmful. These findings suggest that even in motor sequences that can be executed without element-specific stimuli attention attraction enforces stimulus use. The data further supported the assumptions that S-R translation and sequencing systems are racing to trigger individual responses, and that explicit sequence representations include spatial and verbal knowledge.

Response Preparation With Reliable Cues Decreases Response Competition in the Flanker Task

We tested the hypothesis that selective response preparation, based on reliable response cues, reduces response conflict in an Eriksen flanker task. Previous studies of this issue produced inconclusive results because presenting an always valid response cue before the stimulus display turns a choice-response task into a simple-response task, in which full processing of the actual stimulus display is no longer necessary. We conducted two experiments in which we matched stimulus processing in conditions without cues and with reliable cues as far as possible. In both experiments, we presented a nogo target stimulus in 25% of the trials. The different cueing conditions were presented in separate blocks in Experiment 1 but mixed within blocks in Experiment 2. The most important result was the reduction of response conflict as induced by incompatible flanker stimuli in both experiments with reliable response cues. This finding supports the notion of a negative preparation-interference relationship.

Response Preparation, Response Conflict, and the Effects of Irrelevant Flanker Stimuli

The present study explored how response preparation modulates the effects of response conflict as induced by irrelevant flanker stimuli. In Experiments 1 and 2, an unreliable response cue (i.e., valid in 75% of trials but invalid in 25% of trials) preceded the stimulus display containing a target stimulus and different types (i.e., identical, neutral, compatible, or incompatible) flanker stimuli. In Experiment 3, a fully reliable response cue (i.e., valid in 100% of trials) or a neutral cue preceded the stimulus display. There were two major findings. First, valid response cues always improved performance in terms of speed and accuracy when compared to invalid or neutral cues, indicating that the cues were used to selectively prepare the indicated response. Second, response preparation with unreliable response cues did not modulate flanker-induced response conflict in reaction times (RTs; and not consistently in error percentages), whereas response preparation with reliable cues eliminated flanker-induced response conflict. According to these results, only extreme levels of response preparation modulate (flanker-induced) response conflict. The results of computer simulations suggest some boundary conditions for our conclusion.