Problem Solvers

Researchers find surprising smarts in lizards
October 1, 2011
Think again

Think again: Anole lizards are more cognitively advanced than previously believed.

Tropical lizards may be slow, but they aren’t dumb. They can do some problem-solving tasks as well as birds and mammals, a new study shows. A Duke team tested Puerto Rican anoles on several cognitive tasks and found they can learn and remember to solve a problem they’ve never faced before. The results challenge the scientific stereotype that reptiles have limited cognitive abilities and methods for finding food.

The lizards’ success on a worm-based test normally used on birds was “completely unexpected,” says Duke biologist Manuel Leal, an assistant professor of biology who led the study.

Leal tested the lizards using a method he’d previously seen used on sparrows, setting up a wooden block with two wells, one that was empty and one that held a worm but was covered by a cap. Four lizards, two male and two female, passed the test by either biting the cap or bumping it out of the way to reach the worm.

The lizards solved the problem in three fewer attempts than birds typically need to flip the correct cap, Leal says. In addition, while birds usually get up to six chances a day, lizards only eat once a day and therefore get to attempt the challenge less frequently. In other words, if a lizard makes a mistake, it has to remember how to correct it until the next day.

Even when Leal covered both wells, the lizards learned to find the worm by remembering the cap’s color or brightness.

Leal’s experiment “clearly demonstrates” that when faced with a situation the lizards had never experienced, most were able to devise a way to solve the problem. Their ability to “unlearn” a behavior, a skill that eludes some mammalian species, is the mark of a cognitively advanced animal, says Jonathan Losos, a biologist at Harvard University who was not involved in the study.