Professor Robin May of Gresham College recently tackled the elusive biology of laughter, describing it as perhaps the most difficult emotion to define because of its intensely personal and subjective nature. As the second lecture in a series on the biology of emotions, May’s presentation dissected why humans—and several other species—burst into spontaneous vocalizations when faced with specific triggers. Psychologists generally categorize these triggers into two cognitive functions: cognitive rectification and the release of built-up tension. The former occurs when the brain resolves an uncertainty, such as the "aha" moment in a pun where a confusing word is suddenly understood in a new context, providing a sense of relief to a brain that naturally dislikes ambiguity. The latter involves a sudden transition from a perceived threat to a harmless reality, such as watching someone trip or fall in a slapstick routine; the brain recognizes the event as non-threatening and releases the resulting tension through the physical act of laughter.
The neurological machinery behind this process is a high-speed interaction between the ventromedial frontal cortex, which processes complex risks and "cognitive dissonance," and the more primitive amygdala and hypothalamus, which govern basal fear responses. Laughter acts as the "bridge" when these systems reconcile a confusing or frightening stimulus into something benign, effectively signaling to a social group that a situation is safe. Gresham College’s lecture emphasized that this is a universal human trait; regardless of culture or language, the physical act of laughing involves identical muscle tension, tear duct contraction, and repetitive vocalizations starting with an "h" sound. Intriguingly, while individuals may use different vowel patterns like "ha-ha" or "ho-ho," research shows that humans almost never oscillate between different sounds, such as "ho-ha-ho," within a single laugh.
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The evolutionary roots of laughter are ancient, as demonstrated by tickling, a basal form of the emotion that bypasses higher-order cognitive controls and is shared with chimpanzees and even rodents. Robin May noted that rats "laugh" in ultrasound frequencies beyond human hearing, and they will actively seek out social play and tickling from handlers, suggesting that this form of laughter is much older than the higher-order humor associated with jokes. This infectious quality of laughter is further driven by mirror neurons, which fire both when we laugh and when we observe others laughing, explaining why tools like "canned laughter" remain effective at triggering audience responses. However, when this neurological balance is disrupted—through strokes or brain injuries—it can lead to pseudobulbar affect, where individuals experience sudden, inappropriate bursts of laughter that are brief and often detached from the actual context of a situation.
Ultimately, the lecture highlighted that laughter is a fundamental pillar of human health, triggering the release of endogenous opioids, the body’s natural feel-good molecules. Clinical evidence suggests that regular laughter can lower blood pressure, improve cardiac output, and reduce inflammation, even in patients with heart disease. Furthermore, the physical act of laughing reduces cortisol, the primary stress hormone, while boosting the activity of natural killer cells that target viruses and tumors. Laughter even functions as a cognitive enhancer, with studies showing that a brief bout of comedy can significantly improve performance in tasks involving memory and categorization. As May concluded, by embracing the "social signal" of laughter, individuals can simultaneously strengthen communal bonds and improve their own physiological resilience
