Our brain has two different circuits for laughing, and one of them is ancestral

Laughter seems like a simple and automatic act, but neurologically it is a enormously complex phenomenon. It is so complex that we have different types of laughter, since almost all of us have noticed the difference between that uncontrollable laughter that leaves us breathless and the polite laughter that we let out out of courtesy. Now, science suggests that laughter does not depend on a single circuit, but on at least two partially separate networks: one more linked to spontaneous and emotional laughter, and another to voluntary or social laughter.

A question of evolution. This has been the focus of an interesting investigation published in Trends in Neurosciences that pointed out that we live with an “ancestral laugh” that is deeply emotional and is directly related to other primates. But, on the other hand, we have “human laughter” which is involuntary and intended to “look good.”

To get to this point, the researchers analyzed dozens of patients to whom they performed electrical stimulation while they were awake in order to see the areas of the brain that ‘lighted up’ when they began to laugh.

Two networks. The most technical results pointed to the existence of two brain circuits for laughter. The network of spontaneous laughter, which is ancestral, is activated when we hear a brilliant joke or when we are tickled. It is involuntary and purely emotional, causing the most primitive brain regions linked to the reward system and emotions to become active, such as the nucleus accumbens.

On the other hand, the laughter that we emit voluntarily to join a conversation and show empathy activates a circuit that does not depend on emotions, but on motor and cognitive control. Two functions that are much superior on the phylogenetic scale of our species.

In the disease. This division, which was already intuited in classic reviews, explains why some neurological diseases can nullify the ability to laugh at will, but keep spontaneous laughter intact, since it is in totally different places.

With our ancestors. If voluntary laughter appears to be a sophisticated social tool developed by the Homo sapiens To complement language, spontaneous laughter is a direct echo of our evolutionary past. And to understand where this primal laughter comes from, a recent study published in Communications Biology analyzed the acoustics and rhythm of laughter with the aim of comparing laughter sequences in humans and great apes, demonstrating that there is a shared rhythmic pattern.

In this way, when a chimpanzee or a bonobo is tickled, it emits vocalizations whose rhythm and timing bear a striking similarity to the spontaneous laughter of humans, or even the laughter of babies.

Its meaning. This finding suggests an undeniable evolutionary continuity, since laughter did not appear out of nowhere in our species, but rather arose from neural and vocal networks that our hominid ancestors already possessed. Over hundreds of thousands of years, as our brains developed the motor and cognitive areas necessary for complex language, we “hijacked” that emotional vocalization to create a second circuit: controllable, voluntary, conversational laughter.

A missing link. Discovering that laughter has a rhythmic “barcode” shared with apes and two distinct brain pathways is not just a biological curiosity. As points out Nature News Echoing these findings, understanding the evolution of laughter is a direct window into the evolution of vocal control. And the ability to fake a laugh or emit it voluntarily at the exact moment of a conversation requires immense brain plasticity.

That is why understanding how we went from the involuntary gasps of primates to the subtle human laughter could be one of the master keys we have in our hands: how we have been able to develop the language we use today.

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