Why doesn't scratching yourself itch? The latest research finds a neuroscience explanation

The common view is that laughter is a social behavior in mammals that is used to lower the guards of others and build trust
.

Tickling is a direct physical act that stimulates laughter, and not only humans, but also dogs, chimpanzees, dolphins, and mice can sense tickling and make unusual frequencies of sounds
.

In this process, the most curious question is: Why can't we make ourselves laugh?

To figure out how it works, the team recruited 12 subjects, with an average age of 29.
7 years, 4 men and 8 women
.
They are asked to tickle
each other.

So, a strange and ghostly scene happened -

In a neurological laboratory in Berlin, a dozen subjects were asked to raise their hands, remove their shoes and socks, and let another scratch his arm sockets, soles, head, and the outside of his torso, first breathing shortly, then laughing and howling
.

A camera and microphone are on the side, recording the entire process, recording stimuli and reaction time differences down to milliseconds
.
Another breathing belt sensor (AD Instruments) records changes
in chest circumference as subjects laugh.

And this is not a social Darwinist experiment of what the Nazis call "mysticism mixed with reason", let alone a serious interrogation by Stasi, but just an exploration of the perception of human itching, a continuation
of the millennium subject that Aristotle of ancient Greece was curious about.

After some tossing, the experimental results showed that under a single itching in multiple parts other than the head, 95% of the subjects became short of breath within 0.
2s, the facial muscles were lifted upward, the corners of the mouth were upturned, and laughter followed
.

From contact to laughter, the delay is about 500ms, after which the breathing amplitude first falls, and other reactions last more than
1 second.

It is worth mentioning that the facial muscles of the face have begun to activate before the itching touch, and the researchers believe that this is the expected effect of human itching
.

In terms of subjective experience, the researchers first asked subjects to score their own acceptance of itching, without paying attention to the standard value, just dividing the subjective distinction from 0-10
.

The results showed that the higher the itch, the shorter the delay in the body's response to it:

But as the itch increased, the intensity and pitch of the subject's laughter increased, and the dependent variable was positively correlated with
the independent variable.

As for why you scratch your arm sockets without itching?

The researchers first asked the subjects to squeak on one side of their armpit as a comparison, and then let others squeak on the same side and the opposite side of the armpit while they squeaked themselves to observe the response
.

To distinguish between psychological effects and actual scratching, they also added a control group and asked subjects to "pretend" to squeak themselves:

The results showed that compared with simple outsider squeaking, when the subjects began to squeak themselves, even if they were squeaked by outsiders at the same time——

The subjectively felt itch decreases
when the subject's perception of itch becomes weaker and other conditions remain unchanged.
In addition, the body's response to tickling is increasing
.

Scientists also found that compared to subjects "pretending" to scratch themselves, once they are really scratching themselves, their sensitivity to itching will indeed be significantly reduced:

Based on the above observations, the researchers believe that this is because when we scratch ourselves, the brain inhibits itching signals, which causes us to no longer become sensitive to external tickling -

This explains why we don't feel itchy
when we squeak ourselves.

Interestingly, a similar inhibition occurs in conversation, where the brain suppresses external sound signals
when we speak.

At present, the article has been published and attracted a lot of attention and comments
.

Some netizens said that it is easy to make themselves itchy, especially in the abdomen
.

Some netizens said that no matter who touches their feet, they will itch unbearably
.