Simon Effect Test: Can You Ignore Where It Appeared?
The Simon effect is one of the cleanest demonstrations in attention research: you answer based on colour, and the side a stimulus appears on is completely irrelevant — yet when the two disagree, you get slower and less accurate anyway. Your brain maps location to action whether you want it to or not. This test measures your personal Simon cost: the gap between the trials that lined up and the trials that fought you.
A quiet round of Simon Effect Test — Standard. When you start, everything else fades — just you and the task.
No sign-up needed. Press Esc to exit anytime.
Pro is coming — train without limits
- ·Unlimited sessions
- ·Every difficulty level
- ·Full growth history
- ·Ad-free training
How to play
- A coloured circle appears on the left or the right of the field.
- Answer by COLOUR — teal means the left button, amber means the right button.
- Where the circle appeared is irrelevant. It will still pull at you.
- Finish all trials to see your accuracy, speed, and your Simon cost in points.
Frequently asked questions
What is the Simon effect?+
It's the finding that people respond faster when a stimulus appears on the same side as the required response, even when position carries no information at all. The slowdown on mismatched trials is the Simon effect, and it shows that location is processed automatically.
How is the Simon effect different from the Stroop test?+
Both are conflict tasks, but the conflict lives in different places. In Stroop, one feature of the stimulus (the word) fights another feature (the ink). In the Simon effect, the stimulus itself is unambiguous — the conflict is between where it is and which hand you need to move. Stroop is stimulus-stimulus conflict; Simon is stimulus-response conflict.
What does a large Simon cost mean?+
It means the irrelevant spatial information leaked further into your response than average on this run. It's a measure of one specific thing on one specific day, not a verdict about you — fatigue and practice both move it noticeably.
Is this the Simon memory game with the coloured buttons?+
No — completely different thing. That's a 1978 electronic toy where you repeat a growing sequence of lights. This is the Simon effect from cognitive psychology, named after J. R. Simon, and it has nothing to do with memory.
Try another challenge
Schulte Table
Scan a scrambled number grid as fast as you can, in order. Trains visual search speed and peripheral vision.
Stroop Test
Name the ink color, not the word. Trains selective attention and mental control.
Visual Search
Find the one target hidden among distractors. Trains scanning speed and sustained attention.
Multiple Object Tracking
Keep several identical moving dots in mind at once. Trains divided and sustained visual attention.
Cancellation Task
Sweep a dense field and cross out every target. Trains visual scanning and selective attention.
Trail Making Test
Connect the sequence — Part B alternates numbers and letters. Trains processing speed and attention switching.
Change Blindness Test
Two versions flicker back and forth — spot what changed. Trains attention allocation across a scene.