Manuel Leal and Brian Powell have just published a paper in Biology Letters demonstrating that lizards are smart. Before getting to the details, though—here’s the important point: check out the videos! They’re pretty amazing (here, scroll down and click on the videos).
Here’s the story: working with the Puerto Rican trunk-crown anole, A. evermanni, Leal and Powell presented lizards with an experimental apparatus in their home cages with two wells, in one of which was a dead phoenix worm (whatever that is). Next to the well with the worm was a little round disc similar to a poker chip. The lizards learned to go to the well and find and eat the worms. Then the experimenters placed the chip halfway over the well. Again, no problem.
Now comes the cool part. The experimenters completely covered the well containing the worm with a blue chip. Remember, these are Anolis lizards that usually find their prey by looking for movement—they don’t go digging around in the underbrush. Still, four out of the six lizards figured out how to get the mealworm: two of them bit the chip and removed it from covering the well, while two others figured out how to use their snouts as a lever to flip the chip off the well. This is pure problem-solving, and it uses novel behaviors, rather than simply transferring a natural behavior to a new context! And the two lizards that failed to get the worm came up with their own solution, hitting the center of the chip with their snout—but this was ineffective in dislodging the chip.
Once the lizards had learned to find the worm under the chip, the experimenters then conducted a discrimination trial, giving the choice of a blue chip and a yellow chip. Without error, the lizards always went to the blue chip; subsequently, they were presented a blue chip versus a blue-and-yellow chip, and they still had no problem.
Pretty amazing for a lizard, if you ask me, but it gets even better. It turns out that many animals have trouble reversing what they learn. That is, once trained to respond to a particular stimulus, many can’t unlearn that training and learn to respond to the opposite stimulus. In fact, behaviorists consider such reversal learning as an indication of advanced information processing, usually exhibited by cognitively advanced species. To test whether the anoles could reverse their learning, the researchers pulled a fast one and started placing the mealworms under the blue-and-yellow chips, instead of under the blue chips. Two of the four lizards quickly figured it out, and learned to look under the bicolored chip instead of the blue one.
To put this into context, the performance of the lizards in this study was on par with some birds that are generally considered to be good problem solvers, such as corvids, and better than some mammals. In fact, similar reversal learning tests are used as one way of scoring the intelligence of dog breeds—some are good at it, some aren’t. Even some human kindergartners have trouble in such trials.
Pretty darn good for a lizard! I used to say that it was humbling to go into the field and, when trying to catch anoles, to match wits with an animal with a brain the size of a pea, and usually lose. Now I don’t feel so bad.
Leal and Powell conclude by speculating that evolutionary radiation of anoles might be a result, at least in part, of their behavioral flexibility. Certainly an intriguing possibility. If you want to read more, check out Manuel’s post at chipojolab.