Lizard Dreams May Not Be So Different From Your Own

A: Some species of lizards do have two sleep phases, one resembling the dreaming phase of humans, other mammals and birds.

In 2016, a study of the central bearded dragon, Pogona vitticeps, found slow-wave and rapid-eye-movement states that cycled back and forth in 80-second increments over sleep periods of 6 to 10 hours.

In other animals, slow-wave sleep is usually described as deep, dreamless sleep, while rapid eye movements are linked to shallower sleep and dreaming.

Recently scientists in France collected data on brain activity, heart rates and behavioral patterns, including eye movement, in the sleeping Argentine black-and-white tegu (Salvator merianae). The scientists also documented two sleep states, suggesting that the animals do experience something like REM sleep.

In both studies, the researchers suggested that dreaming may have originated with a common ancestor of mammals, birds and lizards, rather than developing independently in various species.