Simple Reaction Time Task

The Simple Reaction Time (SRT) task is the foundational measure of psychomotor processing speed — the time between onset of a sensory signal and the initiation of a voluntary motor response. A single target stimulus (a filled circle) appears at the centre of the screen and participants press the Space bar as quickly as possible.

Because there is only one stimulus type and one response, the SRT isolates the basic speed of sensorimotor processing with minimal cognitive load. Mean RT in healthy adults typically falls between 200 and 300 ms, with variability (intra-individual SD) providing an additional index of sustained attentional consistency.

Each trial uses a variable foreperiod: after the fixation cross the screen goes blank for an unpredictable interval before the target appears, so participants cannot learn the onset time and pre-programme their response. This implementation uses 10 shuffled practice trials with correctness feedback, followed by 40 main-task trials. All timing parameters — fixation duration, foreperiod range, stimulus window, and inter-trial interval — are researcher-adjustable in Open Lab without opening the builder.