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Do you remember a childhood time when you are tickled? Do you like the sensation of being tickled? Who are the ones who tickled you and who would you like to tickle? Have you tried tickling ourselves? Tickle is a familiar sensation to most of us. Yet, we lack a thorough scientific understanding of tickling. A recent article by Dr. Kilteni from Donders Institute and Karolinska institute looked at the status and the prospect of research on tickling, revealing interesting facts about this underrated subfield in neuroscience.
What is tickling?
Despite a history of confusion in defining tickling, scientist now differentiate between two types of sensations associated with “tickle”. The first term, knismesis, means itching. This refers to the sensation of a feather gently gliding on your skin, causing the urge to scratch that area. The second term, gargalesis, is considered as “tickling” in current research. Gargalesis isn’t just a light touch. It’s from a specific, often forceful stimulus that triggers laughter, body movement, and sometimes a reflexive “fight or flight” reaction when applied to sensitive parts like the armpits or soles of the feet. While knismesis can likely be explained by an instinct of removing insects off from the skin to prevent potential harm, the function of gargalesis remains mysterious and it gives rise to many fascinating phenomena. These “fun facts” have driven researchers’ interest in further investigating the mechanisms behind tickling. Here are three examples:
Phenomenon 1: We experience ticklish sensation on certain body parts more than on others.
It seems obvious that foot soles and armpits are among the most ticklish areas for most of us. Other ticklish areas include the neck, sides, stomach, and groin. However, scientists have not come up with a convincing explanation of this. One might think those areas have highest sensitivity to pain, they are more vulnerable during a physical flight, they generate more sexual arousal than other areas or those areas generally receive different stimuli compared to being tickled by fingers. Unfortunately, none of these hypotheses alone can provide sufficient insights into the distribution pattern of our ticklish body map.
Phenomenon 2: We laugh while being tickled, but we may not enjoy it.
You might see someone laughing hard when tickled, but soon it may turn into annoyance, or even crying. It is confusing since we often associate laughter with joy, while tickling was used as a way of punishment during World War II. Scientists explained that the gargalesis laughter we see is more likely a primitive and reflective reaction, like “crying while cutting an onion”. This distinguishes from the more complex, emotional, and social version of laughter that we are familiar with.
Phenomenon 3: We cannot tickle ourselves.
Extensive research has found the evidence of distinct neurological responses between self-touch and external touch. It is likely that we avoid feeling tickled by ourselves to prevent overstimulation. The mechanism of this cancellation might be fascinating. Especially in some cases, such as schizophrenia, people might feel more ticklish by self-touch compared to others. by self-touch compared to others.
Tickling studies: a hidden gem in neuroscience
Currently, large quantities of comparable and comprehensive data for tickling studies are still in demand. Scientists have been working on establishing experimental methods. Attention to this field is beneficial as tickling is by no means trivial. It starts as one of the earliest triggers of laughter in life and serves as a potential gateway to understanding how the nervous system interprets touch, anticipates the world, distinguishes self from other, and generates the emotional and social responses that define us.
Author: Xuanwei
Buddy: Amir
Editor: Dirk-Jan
Translator: Wieger
Editor translation: Lucas
Image: Gabe Pierce
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