TACTILE NEUROSCIENCE · A SYNCHRONY STUDIO
Two hundred milliseconds between movement and touch
Why can't you tickle yourself?
When you move a finger, the brain is already preparing the tactile consequence. In a two-robot experiment, a 200-millisecond delay made touch produced by a person's own movement receive ratings comparable to externally produced touch.
01 Blakemore, Frith & Wolpert · 1999 · read the study
Prediction starts with the movement. Touch can arrive later.
At zero milliseconds, prediction and contact coincide in the model.
The brain rehearses the touch before it arrives.
A movement sends the command that produces the gesture. At the same time, the motor system sends an efference copy to an internal model. The model estimates what will reach the skin, when it will arrive and where.
When the estimate and the tactile signal match, the sensation is less surprising. The touch is still present, yet it receives less weight in the sensory response. When contact arrives late or changes direction, the error grows and the touch can become more salient.
Two robots moved only the timing.
In the 1999 study, participants moved one robot with the left hand. A second robot swept the same piece of foam across the right palm. The researchers changed the link between movement and contact, then asked for relative ratings of the sensation.
| Participants | 16 people |
|---|---|
| Delays | 0, 100, 200 and 300 milliseconds |
| Timing result | Tickle ratings increased from 0 to 200 milliseconds. |
| Comparison | At 200 and 300 milliseconds, ratings did not differ significantly from external stimulation. |
This is a group relationship based on subjective ratings. The study does not provide a universal point at which every person starts tickling themselves.
Can you aim for contact without seeing it?
Start the track and press when the dot crosses the vertical line. After five attempts, you will see the median error between the target moment and your press. It measures your timing in this test, not a clinical response.
The track is stopped. The centre line is the target moment.
Separate touch from expectation.
- 01 Close your eyes and lightly run one finger across the palm of the other hand.
- 02 Repeat with a cotton swab moved by the other hand, then change the rhythm.
- 03 Compare the feeling when you know the exact place and moment with the feeling when someone else changes the timing.
Prediction matters. Tickle has more than one input.
The 1998 fMRI study found more activity in somatosensory cortex during external touch. The robot studies showed that matching movement and contact in time and space changes how the sensation is rated. Later research showed that the internal model can recalibrate after repeated exposure to a delay.
These results support a simple idea: the brain gives different weights to signals it can anticipate and signals that arrive as surprises. The cerebellum contributes to predicting movement consequences, yet the experience of tickling also includes attention, touch, voice and the context between people.
Where the story comes from.
- Blakemore, Frith & Wolpert, 1999The robot study of timing, space and self-produced touch.
- Blakemore, Wolpert & Frith, 1998An fMRI study of central cancellation during self-tickling.
- Kilteni, Houborg & Ehrsson, 2019Rapid recalibration of predicted tactile delays.
- Proelss and colleagues, 2022The human tickle response and the role of self-movement and self-touch.
Method for readers. The page keeps the values reported by the studies and separates its teaching index from the original ratings. The index only shows how far contact moves from the prediction in this page's model.