Spiders Experience REM-Like Sleep and May Dream, Study Finds

Jumping spiders may experience a sleep state similar to REM sleep in humans, complete with rapid eye movements and potential dreaming, according to new research. Scientists observed that Evarcha arcuata spiders exhibit retinal movements and limb twitches during rest, suggesting a sleep cycle previously thought to be exclusive to vertebrates. The study, led by behavioral ecologist Daniela Rößler, found that these spiders enter periodic bouts of retinal activity lasting about 77 seconds, accompanied by leg curls and other movements. This discovery challenges assumptions about the evolution of sleep and consciousness, implying that REM-like sleep may be far more ancient than believed. If spiders do dream, it raises intriguing questions about the content and purpose of their dreams—perhaps replaying hunting scenarios or navigating webs. The findings could reshape our understanding of sleep's role across the animal kingdom, from tiny arachnids to humans, and open new avenues for studying sleep disorders and cognition.