Why you can't tickle yourself: what your brain knows that your skin does not
Force escalation: why your own push feels softer than it is
Press back exactly as hard as you were pressed: it sounds easy. In a London lab, every pair pressed harder, turn after turn. Why does your own push feel so soft?
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1
Miva's game comes from a real lab test. Rono rests one finger on the table, under a small bar. Miva presses down on the bar with her finger. Then they swap: Rono presses down on Miva's finger, just as hard as he felt her press. That is the only rule.
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2
They take turns. Each one is sure to press back just as hard. Yet each push is harder than the one before.
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3
In the lab, six pairs played this game. The push grew by almost 40 percent every turn. After eight turns, it was many times harder than the first.
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4
Nobody cheated. When you press, your brain forecasts the push and turns your own feeling of it down. Your push feels about half as strong as the same push from someone else. So, to match the push you got, you press harder.
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5
That is Miva's point. Two children shove each other on the back seat of a car, and each one says: "I only pushed back as hard as you!" They may both be telling the truth, as each of them feels it. So each push comes out a little harder, and the fight keeps growing.
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6
Morning comes, and the train leaves the mountains. Your brain turns down what it forecasts from your own moves, and it does not only do this with touch. Each of your eyes has a blind spot that you never notice, and your brain paints over it. So how much of this view is a guess? Scientists have tested that too, with your own eyes. It is the next story here: "How perception works: why what you see is your brain's best guess".
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Quick check
You and a friend squeeze each other's hand in turns, each one just as hard as they felt it.
Show the answer
The squeezes grow. Each of you feels your own squeeze as softer than it is, so each one squeezes back harder.
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Go further
When the push is fair.