1Two things your brain does
Your brain predicts the touch your movements will make
These two ideas help explain why the same touch can feel different. This page is a model, not a measurement of your feelings.
It keeps a copy
Every time your brain sends a "move!" order to your hand, it keeps a secret copy — a guess of what you're about to feel, sent ahead of the touch.
Prediction changes sensation
A touch that matches your movement prediction often feels weaker. Surprise is one ingredient in ticklishness; the place, kind of touch and person also matter.
2The two hands
Your own hand vs a friend's hand
The touch on the skin is the same both ways. The only thing that changes is whether your brain already made a guess about it:
You sent the move order, so your brain already has a guess waiting for the touch.
Your brain has no copy of your friend’s movement command. You may still expect the touch, but that is different from predicting your own movement.
3Your turn — be the tickler
A friend tickles your foot
Drag the friend's hand onto the foot and pull the wiggle slider. Watch this illustrative response meter change. It shows the model’s response, not a real person’s ticklishness.
Drag the hand left and right across the foot.
4A new case: a robot you control
What if the touch arrives late?
You send the same move command to two robot brushes. One touches at the expected time; the other pauses briefly before touching. The touch itself has the same strength.
Predict before starting
Which touch will have the bigger response in a model that weakens touch when it matches the expected timing?
Violet shows the expected moment. Coral shows the actual touch. Time is slowed down to make the mismatch visible.
Ready to compare the two touches.