How the lengths game works
A simple face appears for a moment. Its mouth is one of two lengths, and the difference is small but visible. You press one key for a long mouth and the other for a short one. Some correct answers win money.
The twist is in the rewards: one of the two lengths is reported to pay out more often when you get it right, and you are not told which. The game is based on a reward-learning task, which looks at how rewards shape your choices.
How to approach it
Keep your judgement clean from face to face:
- Keep your eyes on the spot where the mouth appears.
- Judge each mouth on what you saw, and answer promptly.
- If you could not tell, make your best guess and move on.
- Notice the rewards, but judge each new face on its own.
Tips for the real lengths game
- Expect it to feel like guessing at times. The difference between the two lengths is meant to be small.
- Sit square to the screen at a normal distance, in good light.
- Use a computer or the Pymetrics phone app rather than a tablet.
Practise the lengths game on CogniPrep
Our Lengths game gives you 90 rounds with 2 seconds each. Two horizontal bars, labelled Left and Right, start from the same left edge, and one is 5 to 15% longer; you tap the longer one. A round with no answer is recorded as unanswered and nothing is deducted, and the end screen splits your accuracy by how close the bars were. It trains fast judgement of small length differences. It has no faces and no rewards, so it does not copy the real game’s reward pattern.