Humans, to judge from the amount we laugh, are apparently the most comical species. We use laughter as the best medicine, we laugh all the way to the bank, and we laugh so hard we forget to cry. From “hahahas” and LOLs, to guffaws, chuckles, giggles, cackles, and snorts, humans do appear to be the kings of comedy.

But laughter is no laughing matter. Despite laughter holding such prominence in human vocalizations, it is surprisingly understudied.

When it does come under the microscope, researchers find that our empirical assessment of laughter shows it to be a more versatile form of communication than just a response to humor. Laughter may actually hold the key to some of the deepest questions in human cognition, such as how language has evolved.

In a recent article published in the Psychonomic Bulletin and Review, Robert Provine presents a theoretical account of the empirical nature of laughter, its evolutionary origins, and how it might help us study language. That laughter is a relatively simple, evolutionarily old aspect of vocal behavior, makes it a nice case study for linguists and psychologists, preferable to the study of actual language, which is vastly more complex than and vastly different from any analogous animal behavior.

First, and most adorably, humans are not the only species that laugh! Bonobos, gorillas, and chimpanzees all laugh, mostly during play.

Animal researchers believe that these vocalizations emulate the vigorous breathing that occurs during rough play. But note how different these vocalizations are from human laughter (which characteristically follows the acoustic structure that, in English, we dub “ha ha.”)

By comparing similarities and differences in the acoustic structure of laughter across species, Provine and other researchers realized that humans can produce multiple vocalizations per breath (“ha ha ha”) whereas apes typically only produce one vocalization per breath, resulting in the in-out panting in the videos.

As speakers of language (and fans of rap) will know, humans are capable of far more than one utterance per breath. When vocalization is limited to one utterance per breath (in addition to sounding like Stevie from Malcolm in the Middle), communication is effortful, laborious, and cannot result in the richly diverse array of meanings that human language now has.

Provine claims that the one vocalization per breath limitation of nonhuman primates comes as a result of the costliness of walking on more than two limbs. By walking erect, humans decouple breathing and walking, freeing up the lungs to laugh and talk. This is known as the bipedal theory of speech evolution.

While laughter is a simple behavior, its uses are diverse, and its properties make it distinct from speech. In one study, subjects were scanned using functional magnetic resonance imaging (fMRI) while listening to human laughter, spoken sentences, or non-verbal utterances. Subjects showed different activation patterns in response to these sounds – laughter was more right-lateralized, for instance.

In another fMRI study, subjects watched videos of actors laughing, either from imagining being tickled, taunting another person, or from joy. The researchers found higher activation in regions of the brain related to emotion processing (the medial prefrontal cortex) during observation of joyful or taunting laughter compared to tickling. They also found more activation in secondary auditory cortex during tickling.

Provine points out that laughter is not under voluntary control. (As a demo, see if you can spot the fake laughs here.)

Laughter, as a response to humor at least, occurs spontaneously, involuntarily, and generally among groups of people. Most people don’t laugh while they are alone. Furthermore, laughing generally occurs throughout conversational speech, but typically does not interrupt phrases. Provine refers to this as the punctuation effect, and considers laughter analogous to breathing as secondary to voluntary speech.

Scientifically, using this approach to study cognition is quite clever. Often, scientists break down hard problems that are difficult to solve into small, solvable chunks. Instead of studying language, which is complex, has incredible variety, and is evolutionarily recent, by studying laughter, we can appreciate some of the structure and mechanisms of vocalization, communication, and even cognition.

According to Provine, laughter may mark a critical change in human evolution, in which laughter changed from panting in chimps to “ha ha” in humans. Other bite-size chunks of human cognition might be equally amenable to this approach, such as tears that denote sadness, which may have come as a result of more face time from bipedal walking.

Although laughter and humor are not equivalent, cat videos, sitcoms, dirty jokes, and bad puns remind us that joy is a powerful and multifaceted human emotion. Nothing feels quite as freeing or satisfying as a bout of uncontrollable laughter. Yet, this innocuous and simple form of communication can be a window into human cognition.

Reference for the article discussed in this post:
Provine, R.R. (2016). Laughter as an approach to vocal evolution: The bipedal theory. Psychonomic Bulletin and Review. DOI: 10.3758/s13423-016-1089-3.