The Science of Laughter: Why We Crack Up

Isn’t it strange that when something is funny, we show our teeth, change our breathing, feel weak in the knees, and might even shed a tear? Why do we laugh, and what purpose does this peculiar behavior serve?

Laughter involves a series of rapid contractions in your abdominal muscles, altering your breathing pattern and increasing pressure in your chest cavity. This expels air, producing snorts, wheezes, or vocal sounds. Because these muscles work harder than usual, they may start to ache. Laughter also impairs reflexes and muscle control, sometimes causing sensations like leg weakness.

But where does laughter come from, and why do we do it? Since there’s no archaeological record of laughter, scientists can’t say for sure, but they have compelling theories. Interestingly, humans aren’t the only animals that laugh. In the 1990s, researchers discovered that rats emit ultrasonic giggles when tickled. Today, we know at least 65 species—mostly mammals and some birds—vocalize during social play.

Primates, our closest relatives, provide key insights. Researchers observed that apes produce laughter-like sounds during play and tickling, leading to the theory that a common ancestor of all great apes had a form of laughter. It likely evolved as a way to signal friendly, non-aggressive intent during physical play, helping to build trust and maintain group harmony.

Over time, human laughter evolved beyond play. As our social groups grew larger and our language more complex, laughter became a way to express nuanced emotions. Today, we laugh in response to amusement, nervousness, confusion, or surprise. Its contagious nature strengthens social bonds—hearing laughter activates areas in the brain associated with emotions, often prompting us to smile or laugh in return.

Studies also show that people laugh more and longer in the company of others, even if they feel the same level of amusement alone. Human laughter is notably louder than the play vocalizations of most animals, perhaps because it functions not just as a signal between individuals but as a broadcast to the entire group.

Fascinatingly, we can distinguish between real and fake laughter based on sound alone. Real laughter stems from ancient brain networks shared with other animals, while fake laughter relies on speech-related pathways. Both types, however, serve important social functions.

Beyond social benefits, laughter is good for your health. It triggers the release of endorphins—feel-good neurotransmitters—and reduces stress hormones like cortisol. Research even suggests frequent laughter improves stress management and cardiovascular health.

Laughter is a universal human behavior, emerging even before babies can speak. While it might not cure every ailment, it strengthens bonds, enhances well-being, and brings moments of joy. So laugh often—unless you’ve got a broken rib. In that case, it’s no laughing matter.