NEW YORK (AP) — It's a question that keeps some scientists awake at night: Do spiders sleep?

Daniela Roessler and her colleagues trained cameras on baby jumping spiders at night to find out. The footage showed patterns that looked a lot like sleep cycles: The spiders' legs twitched and parts of their eyes flickered.

The researchers described this pattern as a "REM sleep-like state." In humans, REM, or rapid eye movement, is an active phase of sleep when parts of the brain light up with activity and is closely linked with dreaming.

Other animals, including some birds and mammals, have been show...