Laughter may be the most contagious of emotional experiences. It involves a collaboration between mind and body. Although there is much we do not know about laughter, scientists do suggest that it is a social signaling system, which helps people to bond and even negotiate. In fact, most social laughter does not result from a joke. It can also occur when we are embarrassed or socially anxious.

Laughter is also great for your brain and your body. As most of us can attest, a good laugh can lift our mood, enhance our social experiences and can even provide a little workout for our bodies. This week, we will look at the role of laughter in improving our brain power as well as all the other benefits from this simple, free activity.

The study of laughter has its own name, “gelotology”. Research has shown that laughter requires coordination of many muscles throughout the body. Some of the physiological changes that occur with laughter include:

· Increased blood pressure

· Increased heart rate

· Changes in breathing

· Reduced levels of certain neurochemicals (catecholamines, hormones)

· Boost to the immune system.

It may improve your health because muscle tension is reduced after laughing. In those with respiratory problems, it can clear mucus and aid ventilation. It may provide a heart workout to cardiac patients. Some hospitals have “humor rooms”, “comedy carts” and clowns to speed recovery and boost morale.

Why do we laugh? Scientists believe that it is a biological adaptation, a trait which provides some type of evolutionary benefit. One benefit can be that it signals social interest, especially in a romantic context. In fact, humor is one of the desired traits in a partner. And gender may affect the way we use humor. It seems that women like men who make them laugh, while men prefer to interact with women who laugh about the jokes they tell them.

Laughter may also have benefits in the short-term memory of older adults. In a 2014 study, older adults were shown a humorous video to see if it influenced short-term memory in the older population. Results showed some improvement in learning ability and significant improvement in delayed recall, with significant decreases in cortisol (related to stress). The results suggested that these changes may result to a better quality of life and that age-associated memory deficits might be decreased with positive, enjoyable and beneficial humor therapy.

Another benefit to the memory is known as the humor effect, a cognitive bias that people will tend to remember information that they perceive as humorous, compared to that which is not seen as humorous. This benefit extends to other types of memory, such as recognition memory (ability to recognize things that you have already encountered) and recall memory (the ability to retrieve past information). Humor can also help enhance verbal information memory such as remembering words and sentences, as well as visual information like pictures and videos.

This effect can be attributed to the improved encoding and retrieval of humorous information, and especially to the increased attention and rehearsal surrounding something that is humorous.

There are other ways that laughter benefits health.

Learning new things: Laughter also induces positive effects in people, which facilitates their ability to learn new things. Laughter and play go hand in hand. With children, this is especially helpful when learning new things. Laughter signals that they are in a safe environment where they can play and learn.

Social connection: Another reason why we may laugh is to connect socially with each other in groups. Groups are necessary for human survival, and as time has gone on, groups have become larger and more socially complex. Some primates groom each other to smooth social interactions, but in a large group, this is difficult. So, for that reason, laughter helps us to establish good relationships with others, and because it is contagious, it can spread through a crowd. (Isn’t a comedy funnier when you are viewing with others?)

Endorphins: But the true answer for a biological mechanism that produces these social effects are neuromodulators that we have discussed many times, endorphins. In research, pain tolerance was tested with participants, and then they were split into two groups. One watched a comedy video clip, where the others watched a neutral factual documentary. Then they took a second pain test. Those watching the neutral clip had less pain tolerance. However, those who watched the comedy found up to 50% more pain tolerance. Although the researchers could not directly measure endorphin levels, they do cite some recent evidence with brain scans suggesting that laughter does release endorphin levels in the brain.

Further studies used the EEG to measure brain activity when they laughed. In each case, the brain produced a regular electrical pattern. Within 4/10 of a second of exposure to something potentially funny, an electrical wave moved through the cerebral cortex, the largest part of the brain. If the wave took on a negative charge, there was laughter. If it maintained a positive charge, no laughter.

During this experiment, researchers observed the following activities in the brain:

· The left side of the cortex (which covers the forebrain) analyzed the words and structure of the joke

· The frontal lobe, involved in social emotional responses, became very active

· The right hemisphere of the cortex carried out the intellectual analysis to “get” the joke

· Brainwave activity spread to the sensory processing area of the occipital lobe (the part of the brain that processes visual signals)

· Stimulation of the motor sections evokes physical responses to the joke.

One area of the brain that seems to be central to laughter is the limbic system. Within the limbic system is the amygdala, the hippocampus, and the thalamus. These connect mediating and controlling activities like friendship, love and affection. The hypothalamus has been identified as the major contributor to loud, uncontrollable laugher.

As for tickling, research out of UCSD constructed a “Tickle Machine” to find out why we laugh when we are tickled, but not when we tickle ourselves. These researchers found a potential reason why this happens. It seems that the brain needs tension and surprise to laugh when tickled. So, when you tickle yourself, you know what is going to happen. No surprise there. There is some evidence that the cerebellum may be involved in this relationship between tension and surprise and laughter.