By Carolyn Y. Johnson, Globe Staff | June 8, 2009
Little Joe clutched the mesh fence that separated him from the outside world. But the 16-year-old western lowland gorilla, famed for his 2003 escape from the Franklin Park Zoo, wasn’t contemplating another jailbreak. He was doing business.
Senior zookeeper Brandi Baitchman had presented him with two colored dowels – gorilla cash in an experiment to see whether Joe could grasp the concept of money. The blue dowel could be traded for monkey chow, a favorite delicacy. The white one was worth nothing.
Without a hint of hesitation, and quicker than a stock floor trader, Joe picked blue. Baitchman slipped a chow pellet into his mouth.
For nearly a year, Joe and other gorillas at the Boston zoo’s tropical forest exhibit have been guinea pigs in experiments exploring the reasoning of gorillas – and the origins of human economic behavior. For years, scientists have examined when and why people take risks, delay gratification, or work for a reward. Harvard University scientists have been visiting the zoo three days a week to learn whether there are roots of such human traits even in a species that never developed its own stock exchange or global monetary system.
“Right now, we’re focusing on what we’re calling gorilla economics,” said Katherine McAuliffe, a Harvard graduate student in the Cognitive Evolution Laboratory who began working with Joe last summer. “What sort of ecological context might select for certain kinds of decision-making?”
The research began with something that seems straightforward, but can take a while to teach a gorilla: the idea that tokens have value. At the zoo, colored baton-sized dowels are primitive gorilla currency: A blue dowel can be traded for coveted monkey chow, made of corn, wheat, and vitamins; a yellow dowel yields a less-appetizing piece of celery; and a white dowel has no value at all.
The dowels allow researchers to test decision-making in ways more comparable to methods used in human experiments, where the prize is often money.
So far Joe and Okie, another male gorilla, have completed their training and understand the tokens. That gives researchers the baseline for a number of studies. Are gorillas risk-prone or risk-averse? Will gorillas work harder for a higher-value token? Researchers will also test whether gorillas treat tokens differently than a food reward.
“My interest in all this is it’s different versions of us,” said Dan Ariely, a behavioral economics professor at Duke University and author of the book “Predictably Irrational.” Ariely studies human behavior, but says the accumulating work on animal decision-making is fascinating, and gives people like himself better ideas of what to study.
“If we can see what they do well and what they don’t do well, we can understand some of our behaviors,” Ariely said. “The interesting question for me is why are we as human beings so risk-averse – what has happened to us that we’re so afraid of risk.”
Already, scientists have examined other closely-related animals’ decision-making abilities, creating theories that the gorilla work can help test.
A 2008 study in the journal Biology Letters tested five chimpanzees and five bonobos, giving them a choice between two overturned bowls, each a different color and shape, and each hiding food. The safe bowl always had four grape halves in it, but the other bowl had either one or seven grape halves in it. The researchers found that chimpanzees were significantly more likely to choose the risky reward, while bonobos were risk-averse.
Scientists theorized that the difference may have to do with the evolutionary pressures caused by each ape’s diet. Chimps forage, but also hunt – which means they are used to taking risks. Bonobos, on the other hand, primarily eat a plentiful type of vegetation, which could explain why they tend to go for the sure thing, picking the safe bowl in the experiment.
Understanding how gorillas make such decisions, and whether they treat tokens differently than monkey chow, may help reveal some roots of human behavior.
“The evolutionary pressures that led to humans have influenced our decision-making” abilities, said Brian Russ, a postdoctoral researcher at Harvard also working on the project. “Looking at gorillas won’t tell us everything, but will give us more information about where we come from.”
That common thread is apparent in the observation area for the gorilla exhibit, where one gorilla sits with legs crossed in an eerie echo of a human pose, the other gorillas playfully snatch away the experiment’s equipment. Joe – who attacked and injured two people after escaping six years ago – bangs on the glass when there is too much movement around the monkey chow that is his reward, perhaps warning people outside the glass to stay away from his lunch.
On a recent morning, after a trial of Joe’s ability to understand currency is finished, Baitchman moves on to the “open forage.” She tosses piles of dowels into the gorilla pen, giving Joe a chance to make a decision about what to do.
Instantly he starts collecting the blue dowels, bringing them to Baitchman where he barters them, one by one, for monkey chow. Then Joe moves on to the yellow dowels, earning celery. Finally, the researchers coax him to bring back the worthless white dowels.
Aside from adding to the body of scientific knowledge about the evolution of decision-making abilities, the experiments provide another benefit – to the gorillas themselves.
Joe, Baitchman noted, does not like to make mistakes. He gets up, stiffens, and then settles down to do the task again.
“It’s really great for them – mentally stimulating,” Baitchman said. “In the wild, they’d be running into problems, things to solve all day long.”