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Simon Task Test
A blue or orange square flashes on the left or right. Answer by the colour — blue means left, orange means right — and ignore where the square appears. When position and colour agree the answer comes quickly; when they clash your brain slows down. Thirty-six trials measure that Simon effect.
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About the Simon Task Test
The Simon task measures how much an irrelevant spatial feature interferes with a choice. Your task depends only on colour, so the square's position should not matter. Yet responses are reliably faster when the square appears on the side that matches its colour, and slower when it appears on the opposite side.
That slow-down is the Simon effect. It shows that even when you try to ignore location, it is processed automatically and competes with the correct response. Answer with the arrow keys, A and D, or the on-screen buttons. Your average reaction time is split into congruent and incongruent trials so you can see the interference directly.