Are We Smart Enough to Know How Smart Animals Are?(79)

So one has to admire one of the most elegant experiments on conformism on wild monkeys, carried out by the Dutch primatologist Erica van de Waal (no relation).37 Teaming up with Andy Whiten, who has been an engine of cultural studies, van de Waal gave vervet monkeys in a South African game reserve open plastic boxes filled with maize corn. These small grayish monkeys with black faces love corn, but there was a catch: the scientists had manipulated the supply. There were always two boxes with two colors of corn, blue and pink. One color was good to eat whereas the other was laced with aloe, making it disgusting. Depending on which color corn was palatable, and which not, some groups learned to eat blue, and others pink.

This preference is easily explained by associative learning. But then the investigators removed the distasteful treatment and waited for infants to be born and new males to immigrate from neighboring areas. They watched several groups of monkeys that were supplied with perfectly fine corn of both colors. All adults stubbornly stuck to their acquired preference, however, and never discovered the improved taste of the alternative color. Twenty-six of twenty-seven newborn infants learned to eat only the locally preferred food. Like their mothers, they didn’t touch the other color, even though it was freely available and just as good as the other. Individual exploration was obviously suppressed. The youngsters might even sit on top of the box with the rejected corn while happily feeding on the other type. The single exception was an infant whose mother was so low in rank, and so hungry, that she occasionally tasted the forbidden fruits. Thus, all newborns copied their mothers’ feeding habits. Male immigrants, too, ended up adopting the local color even if they arrived from groups with the opposite preference. That they switched their preference strongly suggests conformism, since these males knew from experience that the other color was perfectly edible. They simply followed the adage “When in Rome …”

These studies prove the immense power of imitation and conformism. It is not a mere extravagance that animals occasionally engage in for trivial reasons—which, I hate to say, is how animal traditions have sometimes been derided—but a widespread practice with great survival value. Infants who follow their mother’s example of what to eat and what to avoid obviously stand a better chance in life than infants who try to figure out everything on their own. The idea of conformism among animals is increasingly supported for social behavior as well. One study tested both children and chimpanzees on generosity. The goal was to see if they were prepared to do a member of their own species a favor at no cost to themselves. They indeed did so, and their willingness increased if they themselves had received generosity from others—any others, not just their testing partner. Is kind behavior contagious? Love begets love, we say, or as the investigators put it more dryly, primates tend to adopt the most commonly perceived responses in the population.38

The same can be concluded from an experiment in which we mixed two different macaques: rhesus and stumptail monkeys. Juveniles of both species were placed together, day and night, for five months. These macaques have strikingly different temperaments: rhesus are a quarrelsome, nonconciliatory bunch, whereas stumptails are laid-back and pacific. I sometimes jokingly call them the New Yorkers and Californians of the macaque world. After a long period of exposure, the rhesus monkeys developed peacemaking skills on a par with those of their more tolerant counterparts. Even after separation from the stumptails, the rhesus showed nearly four times more friendly reunions following fights than is typical of their species. These new and improved rhesus monkeys confirmed the power of conformism.39

One of the most intriguing sides of social learning—defined as learning from others—is the secondary role of reward. While individual learning is driven by immediate incentives, such as a rat learning to press a lever to obtain food pellets, social learning doesn’t work this way. Sometimes conformism even reduces rewards—after all, the vervet monkeys missed out on half of the available food. We once conducted an experiment in which capuchin monkeys watched a monkey model open one of three differently colored boxes. Sometimes the boxes contained food, but at other times they were empty. It didn’t matter: the monkeys copied the model’s choices regardless of whether there was any reward.40

There are even examples of social learning in which the benefits, instead of going to the performer, go to someone else. At the Mahale Mountains in Tanzania, I regularly saw a chimpanzee walk up to another, vigorously scratch the other’s back with his or her fingernails, then settle down to groom the other. In between the grooming, more scratching might follow. This behavior has been known for a long time and has thus far been reported for only one other field site. It is a locally learned tradition, but here’s the rub: when one scratches oneself, it is usually due to itching, and the act brings instant relief. In the case of the social scratch, however, the performer does not feel relief—the recipient does.41

Primates occasionally learn habits from others that do pay off, such as when chimpanzee youngsters learn to crack nuts with stones. But even then things are not as simple as they appear. Sitting next to their nut-cracking moms, infant chimps are total klutzes. They put nuts on top of stones, stones on top of nuts, and push them all together in a heap only to rearrange them over and over. They gain nothing from this playful activity. They also hit nuts with a hand, or stamp them hard with a foot, which fails to crack anything. Palm and panda nuts are far too tough for them. Only after three years of futile efforts do young chimps have enough coordination and strength to break open their first nut with a pair of stones, but they still have to wait until they are six or seven to reach adult skill levels.42 Since they utterly fail at this task for so many years in a row, it is unlikely that food is the incentive. They may even experience negative consequences, such as smashed fingers. Yet young chimps happily persist, inspired by the example of their elders.