Why there are laughs that are contagious and others that are not

Few human behaviors seem as simple and natural as laughing. We smile inside the mother's womb, and later share smiles and laughter with friends. They help us break the ice with strangers and, sometimes, we surprise ourselves when we burst into laughter without having planned it. However, behind this apparently simple behavior hides a fascinating evolutionary history. According to a study published in Trends in Neurosciences by neuroscientists Fausto Caruana, from the University of Parma's Institute of Neurosciences, and Sophie K. Scott, from University College London, the brain produces two types of laughter with clearly different meanings.For some time now, psychology and neuroscience have distinguished between spontaneous and voluntary laughter. The former is what erupts in the face of a funny situation. The latter, on the other hand, we use as a social tool to show complicity, kindness, or interest during a conversation. The results of this study indicate that these two types of laughter are governed by two different neural systems.

On the one hand, there is a network called the temporal cingulate, which is very primitive from an evolutionary perspective. It is responsible for spontaneous laughter, a type of emotional vocalization that we share with other social mammals. Various studies show that primates and even some carnivores emit sounds and manifest facial expressions formally equivalent to these laughs while interacting with each other. The original function seems to have been to communicate that a situation that could be interpreted as potentially aggressive is, in reality, friendly. In other words, it serves to say “we are playing, not attacking”.This evolutionary antiquity explains why spontaneous laughter is so contagious. When someone truly laughs or smiles, we usually detect it immediately. The rhythm, intensity, and even the way the larynx and breathing coordinate make us perceive it as authentic. It is not just a cultural issue. The brain seems especially prepared to recognize this type of emotional and universal signal.

Laughing out of empathy

However, according to these researchers, humans have gone a little further. As complex language developed, so did another form of laughter, voluntary laughter. This depends mainly on the so-called lateral opercular motor system. It is a brain network associated with the control of speech and vocal movements. It is the laughter we use to lubricate social relationships. It often appears at the end of a sentence, accompanies comments that may not be particularly funny, or serves to indicate empathy and rapport with the interlocutor.This explains why a pleasant encounter between two people is full of little laughs that do not always respond to humor. They fulfill a communicative function. They convey subtle messages such as "I am listening to you", "I am comfortable with you" or "we share this situation". In this sense, voluntary laughter is very similar to language: it is flexible, contextual and can be partially under conscious control.

The story, however, does not end here. The authors also describe another brain region that could act as a bridge between these two systems. It is the pre-supplementary motor area. This connection is especially interesting because it suggests that our most modern capabilities have not replaced ancestral emotional mechanisms, but rather have integrated with them and complemented, or expanded, them.

Perhaps this is one of the keys to the effects of certain laughter-based practices, such as laughter therapy. According to researchers, an initially voluntary laugh could end up activating deep emotional circuits and transform into a genuinely spontaneous laugh. The exact mechanism that could make this possible is not yet known, but both mirror neurons and this brain region that connects both systems could be involved. Mirror neurons are a set of neurons that activate in the same way when we perform an action as when we see another person perform it. They constitute the basic instinctive mechanism of learning by imitation, and they are involved in cognitive and emotional processes such as empathy.

Why laughing makes us feel good

This research also helps to understand why laughing makes us feel good. Spontaneous laughter is associated with neurochemical systems related to serotonin and endorphins. These substances promote interpersonal connection and a good mood, on one hand, and make us more resistant to physical and emotional pain, on the other. Perhaps that is why, after a good while laughing with friends, problems seem a little smaller and some physical discomforts less intense.Beyond curiosity, the authors consider laughter to be a true “Rosetta Stone” for understanding the human brain. By studying it, we can delve deeper into the study of emotions, language, and social relationships, and even into analgesic mechanisms and certain neurological disorders. In short, a simple laugh reminds us that our mind is the result of an extraordinary alliance between a remote evolutionary past and the sophisticated social capabilities that characterize us as a species.