Researchers have discovered that spontaneous and voluntary laughter are controlled by separate regions of the brain, offering new insights into one of humanity’s most universal forms of communication.

Laughter plays a crucial role in social interaction, helping people connect and strengthen relationships. Despite its importance, scientists have long struggled to understand the neural mechanisms behind laughter because genuine laughter is difficult to reproduce under laboratory conditions.

In a new study published in the journal Trends in Neurosciences, researchers analyzed reports from neurosurgical procedures in which awake patients underwent electrical brain stimulation. During these operations, stimulation occasionally triggered laughter, providing a rare opportunity to identify the brain regions involved.

By reviewing these medical reports alongside clinical and animal studies, scientists identified two distinct neural systems responsible for laughter: one associated with spontaneous, emotional laughter and another linked to voluntary, socially controlled laughter.

Study author Sophie Scott explained that researchers have long recognized two different forms of laughter in healthy individuals.

The first is spontaneous laughter—an automatic emotional response that can be difficult to stop once it begins. According to Scott, this type of laughter often erupts unexpectedly and can leave people overwhelmed with amusement. It is also observed in certain neurological and psychiatric conditions, including seizure disorders, mood disorders, Alzheimer's disease, and Schizophrenia.

The second type is voluntary laughter, which people use intentionally during conversations and social interactions. Scott noted that conversational laughter is remarkably well-timed, often occurring at the end of sentences and synchronized with breathing patterns between speakers. Unlike spontaneous laughter, it starts and stops quickly and reflects a higher degree of conscious control.

To better understand the neural basis of these behaviors, researchers examined reports from epilepsy surgeries where doctors electrically stimulated specific brain regions while patients remained awake. Patients could immediately describe their experiences, allowing researchers to link particular areas of the brain to different forms of laughter.

The analysis revealed that spontaneous laughter is generated by a network involved in emotional processing and motor control. This system includes regions such as the pregenual anterior cingulate cortex, nucleus accumbens, and temporal pole. Stimulation of these areas typically produced laughter accompanied by positive emotions, euphoria, and feelings of joy.

In contrast, voluntary laughter was associated with brain regions primarily responsible for controlling movement, including the rolandic operculum, globus pallidus, and presupplementary motor area. Stimulating these regions triggered laughter-like behavior without producing positive emotional feelings.

Researchers suggest that the spontaneous laughter network may represent an evolutionarily older system that developed during social play among animals. Similar laughter-like vocalizations have been observed in several mammalian species, where they appear to reduce aggression and strengthen social bonds.

The voluntary laughter network, however, overlaps with areas involved in speech production, supporting the idea that it evolved to facilitate purposeful communication and social interaction.

Co-author Fausto Caruana said the findings may help scientists better understand neurological and psychiatric disorders characterized by abnormal laughter patterns. He also suggested that the research could provide valuable clues about how the brain uses vocalizations for social communication.

The researchers are particularly interested in the connection between laughter and pain relief. Previous studies have shown that laughter can function as a natural painkiller. Notably, the anterior cingulate cortex—identified as part of the spontaneous laughter network—is also involved in the brain’s internal pain-regulation system.

According to Caruana, future research will focus on exploring how laughter reduces pain and identifying the neural circuits responsible for its analgesic effects.