Lemurs are among the world's most primitive living primates. In fact, fossil records suggest that lemurs may have more in common with primate ancestors that lived millions of years ago than they do with today's monkeys and apes. However, a new study published in the April issue of the Journal of Experimental Psychology: Animal Behavior Processes (Vol. 32, No. 2) shows that lemurs might share one surprising cognitive capability with chimps and humans: the ability to deceive.
"These studies show they can have advanced cognitive skills," says Emilie Genty, PhD, a primatology postdoctoral student at the University of St. Andrews in Scotland. Or, perhaps tricking others doesn't require the brainpower that researchers previously thought it did, she notes.
Genty and her colleagues began the experiment by training three lemurs to point to an overturned bowl that hid a raisin. Genty hid the raisin in view of the lemur, and then trained the animals to gesture toward the bowl that covered the raisin. Once the lemurs pointed to the right bowl at least 80 percent of the time, Genty introduced a second trainer. She wore a white lab coat, and approached the lemur after Genty hid the raisin. This cooperative trainer placed her hand between the two bowls and waited for the lemur to point to the bowl containing the raisin. If the animal chose correctly, she gave it the raisin. If not, she took the raisin away.
Sometimes, in place of the cooperative trainer, a competitive trainer would approach the animal. He was dressed in a dark jacket, hat and sunglasses. This trainer would snatch up the raisin and pretend to eat it if the lemur pointed to the correct bowl. In response, one of the three lemurs began gesturing toward the incorrect bowl, and Genty rewarded it with a raisin. A second lemur stood by the bowls, but wouldn't give information about the location of the raisin, and a third stayed at the bottom of the cage, refusing to participate.
However, all three continued to point to the correct bowl when working with the cooperative trainer.
Though the study was done with a small sample of lemurs, it shows that animals that are only distantly related to humans can learn to deceive. Anecdotal evidence suggests that pets might be in on the game too-as is the case with a cat that meows at a door and then steals its owner's seat when he stands up to open it, Genty notes.