Animal behaviour (I)

Reptiles are more intelligent than previously thought

Jul 14th 2011 | from the print edition

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IT IS no compliment to call someone lizard-brained. The reptilian mind is usually equated in the human one with traits like aggression, dominance and sexual appetite. That analysis was given currency in the 1960s when Paul MacLean theorised that the human brain has three levels, the most basic—both functionally and literally (because it is at the bottom of the organ)—being the “reptilian” part, composed of structures called basal ganglia.

MacLean’s analysis is not much believed now by neuroscientists, but it has stuck in the popular imagination. And it has also, subliminally, affected research. For, until recently, no one had actually thought to ask by experimentation just how intelligent reptiles really are.

That omission has just been corrected by Manuel Leal and Brian Powell of Duke University, in North Carolina—and the result is intriguing. In a paper published in Biology Letters Dr Leal and Dr Powell suggest that lizards are at least as intelligent as tits, a group of birds that has been well examined in this respect.

Dawn's early light
Mechanical advantage
Atlantis's last hurrah
»Cold-blooded cunning
Sexual appetite

In their study, the two researchers put a species called Anolis evermanni through a triathlon of cognitive tests of the sort used on tits (and other birds and mammals that ethologists wish to investigate). First, the reptiles had to learn how to extract a tasty grub from a container. Then, they were taught to associate the grub with a particular colour. Finally, they were taught to dissociate it from that colour and learn that a different colour was the giveaway.

The lizards were able to manage all three tasks with ease—matching the performance of tits in similar tests. Indeed, in getting at the grubs several of them worked out a form of behaviour never seen in nature, employing their snouts as levers to lift an obstacle (ie, the lid of the container).

Having established that lizards are at least as clever as birds at such simple tasks, Dr Leal hopes to go on and explore the evolutionary forces behind lizard intelligence. He does, however, have a problem—and it is one that might help to explain why, besides phylogenetic prejudice, the lizard mind has not been properly investigated before. Tits, being warm-blooded, have to eat a lot and thus have a strong incentive to collaborate with researchers in such experiments. The average lizard, by contrast, is happy to consume a single grub a day. It may therefore be some time before the next paper appears on the subject.