It tickles when someone else touches you, but not when you touch yourself, because your brain dampens self-generated touch signals.
Understanding Ticklishness
The sensation of tickling is complex, and it involves more than just physical contact. It's a combination of sensory input and the brain's interpretation of that input. The key difference between being tickled by someone else and tickling yourself lies in how your brain processes these inputs. When someone else touches you, there is an element of surprise and unpredictability that your brain interprets as a potential threat. This causes your brain to heighten your sensitivity. When you touch yourself, your brain predicts the sensation, which is why it's not perceived as a tickle.
The Role of the Brain
The brain actively differentiates between self-generated and externally generated touch. Here's a closer look at the mechanisms involved:
Predictive Processing
- When you move to touch yourself, your brain anticipates the sensory input. This predictive processing reduces the sensitivity to the touch.
- This dampening effect is referred to as tickle attenuation, according to research from Kilteni, as cited on 08-Feb-2021. This was his first study on the topic.
Sensory Prediction Error
- When someone else touches you, your brain does not predict the exact timing, location or intensity of the touch. This unexpected input creates what is known as a sensory prediction error.
- This error heightens your brain's reaction, making the touch feel more ticklish.
The Sensory System
- Nerve Endings: Specialized nerve endings in your skin detect touch and pressure. These signals are sent to your brain for processing.
- Somatosensory Cortex: This area of the brain processes all incoming sensory information, including touch.
- Cerebellum: While not cited in the original text, this part of the brain is also crucial. It is involved in predicting the consequences of our actions, and plays a key role in sensory attenuation.
Practical Insights and Examples
| Touch Source | Brain's Response | Perception |
|---|---|---|
| Self | Predicts the touch | Reduced ticklishness |
| Other | Does not predict touch | Increased ticklishness |
Why This Matters
- Understanding tickle attenuation helps us learn more about how the brain distinguishes between self and other.
- Research into this area may have implications for understanding conditions where self-perception is altered, like schizophrenia.
Conclusion
In essence, the brain's ability to predict the sensory consequences of self-generated actions dampens the ticklish sensation. This predictive mechanism is what distinguishes the tickle experience when someone else touches you versus when you touch yourself.
