Where does human laughter come from

The study found that the more people who carry the “s” allele, the more often they laugh. Couples who often make fun of each other and laugh together often have a longer and happy marriage. The study also found that an increasingly unusual sense of humor is likely to be an early sign of Alzheimer’s.

The special behavior of laughing was gradually formed in the process of human evolution. So, why did humans derive this behavior?

How does laughter come out

Studies have found that 80% of human laughter comes from emotions such as embarrassment, disappointment, helplessness, jealousy, and anger. Even when we are in a good mood, the effective time of our laughter lasts only 10 seconds, and the rest of the time is to restore muscle. In order to measure the degree of laughter, Japanese researchers set up a unit of measurement “aH”, which is “aha”. The researchers said: “We found that children laugh very naturally, 10 aH per second, twice that of adults.”

The description of laughter in the book “Perceptual Growth Model” is: the scene at the time produced the excitement energy needed to express a smiling face and gathered → the excitement energy was attracted into the efferent motor nerve → effector → showed a smile.

In general, scientists have three views on the perception of laughter:

Response to threats. Some scientists have discovered that in other animals, a friendly physical attack can cause laughter. This shows that laughter is often accompanied by strange behavior or mental disorders.

Trust in the environment. Physiologists have found that when things seem fun, even anxiety can make people laugh. There is also evidence from muscles and nerves that show that laughter can only happen in an environment that people consider safe and trustworthy.

The stress of “contradictions”. In the tickling experiment, the subjects often laughed with physical discomfort.

The level of laughter depends on genes

Listening to the same joke, some people laughed, while others looked confused. What is causing such a difference? A study showed that the intensity of people’s emotional response may be related to serotonin.

Serotonin is an important neurotransmitter in our brain, and its activity is indispensable for the involvement of a protein called 5-HT transporter-the latter can recover serotonin released by nerve synapses, thereby regulating the synaptic cleft The concentration of neurotransmitters. A polymorphic region in the gene SLC6A4 that encodes this protein: 5-HTTLPR, is crucial.

In the population, there are individual differences in the DNA sequence length of the 5-HTTLPR region, which can be divided into two types: the shorter “s” type and the longer “l” type. Some studies have found that people with “s” alleles (that is, individuals with “ss” or “sl” genotypes) have more sensitive emotional responses, and they are more susceptible to environmental and personal experiences.

The researchers conducted an experiment in which they set up three tasks for three different groups of subjects and recorded their facial expression changes at the same time. The subjects in the first group need to watch 20 funny comic strips; the subjects in the second group need to watch a segment of the movie. Compared with the comic strips, the humor is more subtle; the subjects in the third group are husbands and wives. Asked to talk in the laboratory based on specific marriage life topics.

After the behavioral test, the researchers collected saliva samples from the subjects for DNA sequencing. Sequencing results and facial expression statistics showed that the more s-type alleles carried by the subjects, the more often they laughed.

In addition, American researchers have found that couples who often make fun of each other and laugh together tend to have longer and happy marriages.

Low smile or a sign of dementia

A University of London study found that an increasingly unusual sense of humor is likely to be an early sign of Alzheimer’s. This study investigated the family and friends of 48 patients with Alzheimer’s disease. Many family members and friends of the patients were aware of changes in the patient’s sense of humor.

This study found that patients often laugh in situations that are “obviously untimely.” “In the early days, they just laughed at things that were a little interesting. Now, they laughed at things that weren’t interesting. They even said,’I just want to laugh, I don’t even know why I laugh. “One interviewee said, “I got a serious burn once, and they thought it was very interesting.”

The researchers therefore believe that after suffering from Alzheimer’s disease, the mature sense of humor that the patient had acquired through training has disappeared.

A doctor from the Alzheimer’s Disease Research Organization in the United Kingdom said that if you notice a similar behavior change in someone at home, you should contact your doctor immediately.