Originally written by Tim Newman on January 18, 2017
We laugh at jokes (albeit not all jokes). We can also laugh sarcastically, nervously, when we are stressed, or even for no reason at all. Our laughter may be uncontrollable or maniacal, and it might also be forced, faked, or purposefully prolonged.
The laugh is so pervasive that it can hardly be ignored by scientists; it crosses all boundaries. Humans from every culture on earth laugh. Babies who are blind and deaf, having neither seen someone laugh nor heard the sound of laughter, still laugh. Something as ubiquitous as this odd expulsion of sound and air must be important.
In this article, we will take a brief look at the origins of laughter and what happens in the brain when we are amused. We will also take a wander through the scientific literature to examine whether laughter has the ability to relieve medical conditions.
Laughter is a trait we share with our nearest cousins, the great apes. This means that it was, more than likely, an ancient invention that has been retained over millennia. As with most things that evolution preserves, it must be useful.
One odd but insightful study involved tickling a variety of ape species and human infants. The researchers then compared the sounds of laughter that were generated. Interestingly, species more closely related to ourselves (such as bonobos and chimpanzees) had more similar acoustic data to humans when compared with our more distant relatives (gorillas and orangutans, for example).
As the authors explain, their data matches “the well-established genetic relationships of great apes and humans.”
As social animals go, humans congregate in fairly large groups. One theory has it that laughter (along with speech) helped us to bond more efficiently. Rather than having to physically groom each individual in our tribe, we could stand within earshot and make each other laugh. Bonds could be built at a distance and with multiple players.
Whether this theory holds water or not will be difficult to prove, but there is no question that laughing brings people closer together. Laughter helps to build relationships and, when living in a group on the savannah, bonding successfully can be the difference between life and death.
This ability of laughter to act as social glue also helps explain why humans find it so very easy to identify a faked, forced, or overly prolonged laugh.
Although some jokes may need our full cognitive ability and a dose of lateral thought, the act of laughing itself seems to be a primitive thing.
It will come as no surprise that an action as complex, varied, and meaningful as laughter is not limited to a single region of the brain. Researchers have, however, made efforts to understand the range of areas that are involved.
One study, published in the journal Cerebral Cortex, used MRI scans to investigate which regions of the brain were at work. They split participants into three groups: the first group was tickled on the sole of the foot and given permission to laugh, the second group was tickled but told to suppress their laughter, and the final group was asked to laugh voluntarily without being tickled.
In the brains of the first group – participants of which were laughing genuinely – certain regions were activated more consistently when compared with the other two groups. These were:
In this study, they also measured activation of the periaqueductal gray matter during voluntary and involuntary laughter, but not when laughter was prevented. Interestingly, periaqueductal gray matter is known to play a role in analgesia. In fact, the region is a target for brain-stimulating implants to treat patients with chronic pain.
During laughter, regions of the ventromedial prefrontal cortex are activated, releasing endorphins – which are famed for decreasing pain and increasing euphoria.
Involvement of the hippocampus and amygdala are also worthy of note; these are part of the limbic system, an ancient section of the brain involved in the control of deep-seated emotions, feeding, and other survival-critical roles.
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