Simon Task

The Simon task is a classic measure of cognitive control and stimulus-response (S-R) compatibility, first described by Simon and Rudell (1967). On each trial the participant responds to a task-relevant, non-spatial feature of a stimulus (here, its colour) using a left or right key, while the stimulus's spatial location — which is entirely irrelevant to the task — varies from trial to trial.

Because the stimulus location automatically activates the spatially-corresponding response, trials on which location and response side agree (congruent) are answered faster and more accurately than trials on which they conflict (incongruent). The difference in reaction time between incongruent and congruent trials is the Simon effect — a robust index of the cognitive control needed to resolve the conflict between an irrelevant spatial code and the correct response.

This implementation uses the widely-adopted visual colour variant (as popularised by tools such as PsyToolkit): a coloured circle appears to the left or right of a central fixation cross. Participants press the Left-Arrow key for one colour and the Right-Arrow key for the other, regardless of where the circle appears. On congruent trials the circle appears on the side of its colour-mapped response (e.g. a Blue circle — mapped to the Left key — on the left); on incongruent trials it appears on the opposite side.

Note on lineage: the original Simon & Rudell (1967) task was auditory — participants heard the word "left" or "right" in one ear and responded to its meaning while ignoring the ear of presentation. The visual, lateralised colour version used here is the form most researchers reach for today; it measures the same S-R compatibility construct with a language-independent stimulus.

The template ships with a short 4-trial practice block, followed by 24 shuffled main trials balanced across the four design cells (2 colours × 2 locations). Fixation, response-deadline and inter-trial-interval durations are exposed as re-usable parameters so researchers can adjust timing in the Open Lab study builder without editing individual screens, and all participant-facing text is exposed as translatable parameters.