Abstract
In the Simon task, participants respond faster when the task-irrelevant stimulus position and the response position are corresponding, for example on the same side, compared to when they have a non-corresponding relation. Interestingly, this Simon effect is reduced after non-corresponding trials. Such sequential effects can be explained in terms of a more focused processing of the relevant stimulus dimension due to increased cognitive control, which transfers from the previous non-corresponding trial (conflict adaptation effects). Alternatively, sequential modulations of the Simon effect can also be due to the degree of trial-to-trial repetitions and alternations of task features, which is confounded with the correspondence sequence (feature integration effects). In the present study, we used a spatially two-dimensional Simon task with vertical response keys to examine the contribution of adaptive cognitive control and feature integration processes to the sequential modulation of the Simon effect. The two-dimensional Simon task creates correspondences in the vertical as well as in the horizontal dimension. A trial-by-trial alternation of the spatial dimension, for example from a vertical to a horizontal stimulus presentation, generates a subset containing no complete repetitions of task features, but only complete alternations and partial repetitions, which are equally distributed over all correspondence sequences. In line with the assumed feature integration effects, we found sequential modulations of the Simon effect only when the spatial dimension repeated. At least for the horizontal dimension, this pattern was confirmed by the parietal P3b, an event-related potential that is assumed to reflect stimulus–response link processes. Contrary to conflict adaptation effects, cognitive control, measured by the fronto-central N2 component of the EEG, was not sequentially modulated. Overall, our data provide behavioral as well as electrophysiological evidence for feature integration effects contributing to sequential modulations of the Simon effect.
Highlights
Stimulus–response compatibility (SRC) paradigms like the Simon task (Simon, 1969) are helpful research tools to investigate action control
We investigated the contribution of conflict adaptation and feature integration effects on sequential modulations of the Simon effect by using different spatial dimensions
We examined whether sequential modulations of the Simon effect (RT) and of spatial correspondence effects on accuracy and ERPs occur irrespective of a trial-by-trial change of the spatial dimension or whether such effects are only evident in trials with an unbalanced proportion of unbinding processes
Summary
Stimulus–response compatibility (SRC) paradigms like the Simon task (Simon, 1969) are helpful research tools to investigate action control. In the Simon task, participants are asked to respond to non-spatial stimulus features (e.g., color or letter-identity), which are mapped onto spatially arranged response keys. Dual-route models (Kornblum et al, 1990; De Jong et al, 1994) assume that S–R transmission in the Simon task proceeds via a direct and an indirect route. While the direct route operates via automatic processing of the irrelevant spatial stimulus information, the indirect route involves controlled processing of the task-relevant stimulus features. It follows that both routes activate the same response in corresponding trials, whereas they activate opposing response tendencies in non-corresponding trials. The prolonged RT observed in non-corresponding Simon trials are assumed to result from this response conflict (Kornblum et al, 1990; De Jong et al, 1994)
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