- Fully comprehending laughter requires understanding why it takes the somewhat unusual form that it does.
- Laughter evolved as a fundamentally vocal expression rather than a visual one.
- Auditory signals were probably more effective in communicating feelings of mutual vulnerability during play.
In prior posts, I’ve discussed the evolution of laughter as a signal expressing a sense of mutual, or shared, vulnerability, both in humans and other members of the great ape family. Yes, human laughter is somewhat unique structurally; the other great apes have an in-and-out panting laughter, whereas we are mostly exhaling HEE-HEEers, HO-HOers, and HA-HAers, with countless minor frills and variations (Provine, 1996). Still, a keen observer will recognize both ape and our laughter as serving essentially the same function.
We shouldn’t assume, however, this message had to have taken the characteristic form that it did. We must wonder about the dozens of other strategies evolution could have used to communicate this sentiment. Indeed, why should our most explicit expression of mutual vulnerability be primarily a vocal rather than, say, a visual signal? Why did we not evolve to, instead, simply cross our eyes, raise an eyebrow, wiggle our ears, or wrinkle our nose whenever we felt amusement?
Vocal versus visual
To answer this question, we are again obliged to go to the source. If we use the living great apes as a model, we might surmise that our common ancestor likely had a variety of potential visual signals with which to work. In chimpanzees, for example, there are whole-body expressions such as bowing, crouching, and the presenting of hindquarters (Tanner, 1981). They use gestural signals like foot-stomping, waving or extending hands, and breaking branches. And then there are tactile contact signals such as hugging, touching or patting with the hands, simple caresses or body contact, and of course, kissing (de Waal, 1997; Fouts, 1997). The great apes have faces nearly as expressive as ours. Their eyes and brows appear to convey a variety of emotional states similar to those of humans. They can pout and purse their lips and use them to cover their teeth completely, partially, or not at all (de Waal, 1997).
So, with such a range of nonvocal options, why should the signal for mutual vulnerability be an auditory one?
There are several possibilities. It could be these various visual expressions were already assigned important meanings prior to the advent of laughter. Today’s monkeys and lesser apes use facial expressions and body movements to communicate emotions such as fear, confusion, concentrated interest, sorrow, fatigue, anger, submission, and anxiety. For early great apes to modify one of these expressions and give it a substantially new meaning may not have been feasible. It would have been too confusing.
A more likely reason may have something to do with the general nature of visual signals. To be effective, the receiver must be looking at the sender—at their body for postural or gestural communiqués, and directly at the face for facial messages. These constitute inherent limitations. The intended receivers might be looking at the sender, but they might not. They might wish to see a particular expression, but be obstructed by other group members or some physical object in the area—a branch or tree trunk, for example. Indeed, they might not be aware of the sender’s presence at all. Or maybe the intended receivers don’t want to look for some reason. They may be upset with the sender, or they may be busy looking for food or watching out for potential predators. In most cases, receivers of visual communications must be proactive.
In contrast, vocal signals can be heard and interpreted by everyone within a given range, one that is determined solely by the message’s volume. It’s much less likely that one would be unable to receive and interpret an audible message provided its form is sufficiently distinct from other vocalizations. In this sense, potential receivers can be much more passive and still acquire the information intended by the sender.
Consider the situation of two young gorillas engaging in a bout of playful wrestling. Because laughter is vocal, the tickler need not have visual contact with his or her victim’s face to know that the attack is being correctly interpreted as playful. Nor would the tickler need to adopt a particular body posture or facial expression during what would likely be an extremely chaotic, though friendly, altercation.
Moreover, a vocal signal such as laughter can go beyond those immediately involved in the physical exchange. Supervising adults, with the ability to quash what they misinterpret as an aggressive encounter, would be much more effectively informed about the nature of the physical contact with a vocal signal than they would with a visual one. Because the freedom to play generally benefits those who engage in it, a vocal signal identifying the activity would be favored by natural selection. Rather than having to constantly monitor what would likely be rapidly changing facial expressions and body postures, adults could rely on this unique vocalization, one that expresses each participant’s sense of amusement rather than aggression or fear.
Indeed, while the one on the receiving end of such playful attacks tends to laugh most actively, (Provine, 1996), the affable assailant often does so as well. Each party affirming they both have vulnerabilities advertises to all within earshot the exchange is a good-natured one. It’s an arrangement that benefits everyone involved.
This post was drawn from Chapter Seven of Why We Laugh: A New Understanding.
© John Charles Simon
de Waal, F. B. M. (1982). Chimpanzee Politics: Power and Sex Among Apes. New York: Johns Hopkins UP.
Fouts, R. (1997). Next of Kin: What Chimpanzees Have Taught Me About Who We Are. New York: William Morrow and Company.
Provine, R. R. (1996). Laughter. American Scientist 84: 38 – 44.
Simon, J. C. (2008). Why We Laugh: A New Understanding. Starbrook Publishing.
Tanner, N. M. (1981). On Becoming Human. Cambridge: Cambridge UP.