You can’t tickle yourself because your brain predicts your own movements and cancels the sensation.
Why
When you move, your cerebellum predicts the sensory result and cancels the response in your brain. So the touch doesn’t feel surprising.
Research
A 1998 study by Sarah-Jayne Blakemore found less brain activity when people touched themselves than when a machine touched them.
Other
Someone else’s touch can’t be predicted, so it tickles.
Trick
A time delay makes self-tickling work with a robot.
Types
Knismesis (light) and gargalesis (laughter).
The neuroscience
You cannot tickle yourself because your brain predicts the sensory result of your own movement. The cerebellum creates a prediction and sends a signal that cancels the sensation, a mechanism called sensory attenuation. When someone else tickles you, the prediction is absent, so you feel the touch strongly.
- A 1998 study in Nature Neuroscience by Sarah-Jayne Blakemore, Daniel Wolpert and Chris Frith showed that tickling a person with a robotic arm was less ticklish when the person’s own movements controlled it without delay, and felt more ticklish when a delay was added.
- Brain scans show reduced activity in the somatosensory cortex and anterior cingulate cortex for self-touch.
- People with schizophrenia can sometimes tickle themselves, which researchers link to difficulty distinguishing self-generated actions.
Types and tricks
Two types of tickle exist: knismesis (light, feather-like touch) and gargalesis (heavy laughter-inducing). Feeling tickled by a delayed robot or an unpredictable device, or when relaxed and uncertain, can work. Rats also laugh at 50 kHz ultrasonic calls when tickled, shown by Jaak Panksepp.
The neuroscience
The cerebellum predicts the sensory result of your own movements and cancels the response, so self touch feels less ticklish. Research by Sarah-Jayne Blakemore showed that people find robot-delivered touch more ticklish when delayed.
Types and tricks
There are two types: knismesis (light) and gargalesis (heavy laughter). Self tickling is rarely effective.
The brain’s prediction
You cannot tickle yourself because the brain predicts the sensory result of your own movement. The cerebellum creates a forward model, comparing the expected touch with the actual one, and reduces the response in the somatosensory cortex and the anterior cingulate. Studies by Sarah-Jayne Blakemore and others in 1998 used fMRI and found less activity when subjects touched themselves than when a machine did it.
Related findings
If a delay or a change in direction is added between a person’s movement and the touch, a self tickle feels stronger. People with schizophrenia can tickle themselves more easily, which researchers link to altered self other distinction. Tickling has two types: knismesis, a light itch feeling, and gargalesis, the laughter provoking kind. Rats also laugh when tickled, according to Jaak Panksepp’s work.
Based on data from Blakemore, Wolpert and Frith in Nature Neuroscience and Panksepp’s research
