What causes us to laugh and why?

Every individual varies in their neurological pathways through their "boxes" in their brain to reach the output of laughter from a number of different inputs. Laughter is caused by certain visual or audio stimuli, often by perception of the unexpected or the incongruous. A surprise in expected input can result in an emotional change, however major or minor. As H. Spencer says in his Physiology of Laughter, "the nervous system in general discharges itself on the muscular system in general: either with or without the guidance of the will" (1). Incongruous input causes an emotional change, and in the case of humorous response, resulting in the contraction of facial muscles and certain muscles in the abdomen. The epiglottis half closes the larynx, resulting in giggling, guffawing, or gasping, and tear ducts are activated. These outputs of the nervous system we refer to as laughter can be arrived at through a number of pathways through the boxes of the brain, fabricated in each individual throughout their life to that point.


Although different parts of the brain are involved in understanding different types of input necessary for the laughter output, the median ventral prefrontal cortex is a key player in the physical response. Using functional magnetic resource imaging, scientists at the Institute of Neurology in London scanned the brains of people listening to jokes, and found that for example, semantic jokes, playing on the meaning of words, activate the posterior temporal lobe, and puns, which work with the sound of words, activate the left inferior prefrontal cortex. At any rate, however the input is initially processed to be found incongruous with normal expectations, the median ventral prefrontal cortex is signaled to handle the response. This area is incidentally also involved in the reward system in humans and primates, explaining why humor and laughter are enjoyable and continue to be sought as a form of entertainment .

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