This finding has significant implications. It suggests that chickens, often overlooked or dismissed as unintelligent, have neurological patterns that echo our own. It also challenges assumptions about what it means to be conscious, to feel, and to need rest in order to thrive.

What Is REM Sleep?

REM stands for rapid eye movement, a distinct stage of sleep characterized by low muscle tone, quick movements of the eyes under the eyelids, irregular breathing, and heightened brain activity. In humans and other mammals, REM sleep is associated with dreaming and plays a key role in learning, memory consolidation, emotional processing, and brain development.

REM sleep is not exclusive to humans. It has been observed in many mammals and birds, and increasingly, in reptiles and even some fish. The presence of REM sleep across different evolutionary branches suggests it serves vital neurological functions.

How Do We Know Chickens Experience REM Sleep?

Scientists have studied avian sleep for decades, using tools such as electroencephalograms (EEGs) to monitor brain activity in sleeping birds. Chickens, with their accessible domesticated status and relatively large brains for birds, have been prime subjects.

In studies, chickens exhibited both non-REM (slow-wave) sleep and REM sleep during their rest cycles. During REM phases, their brain activity closely resembles wakefulness, but the body remains still. The eyes twitch under closed lids, and muscle tone drops—classic indicators of REM.

One well-documented experiment published in the journal Nature (1970s) observed domestic chickens under laboratory conditions and showed that REM sleep occurred cyclically throughout the night, alternating with non-REM stages, just as it does in mammals. More recent research has reaffirmed these findings with modern technology and non-invasive methods.

Chickens were also found to experience unilateral sleep, where one half of the brain rests while the other stays awake—a trait shared with other birds. Yet even within this pattern, they experience full REM episodes when completely at rest.

Why REM Sleep Matters for Chickens

REM sleep isn't just a physiological curiosity. It’s a marker of cognitive complexity and emotional processing. In mammals, a lack of REM sleep has been associated with memory loss, stress, impaired immune function, and emotional dysregulation. While chickens have not been tested for dream content in the way humans or lab rats might be, the existence of REM sleep implies a need for deep, uninterrupted rest to maintain brain health.

The presence of REM sleep also suggests that chickens may form and retain memories, process social experiences, and potentially dream—though we can't yet say what a chicken might dream about. Their sleep architecture reinforces what behavioral studies already show: chickens are smart, social animals with rich internal lives.

Implications for Animal Welfare

In the context of industrial poultry farming, these findings are particularly important. Chickens raised in confined spaces, under constant artificial lighting or stress, often experience fragmented or disrupted sleep cycles. Without sufficient REM sleep, these birds may suffer from chronic fatigue, weakened immune systems, or behavioral issues.

Providing a dark, quiet, safe environment for roosting isn’t just about tradition—it’s a biological necessity. Backyard chicken keepers who notice their birds perched quietly with eyes closed and the occasional twitch may well be witnessing a sleeping brain at work, cycling through deep neurological processes.

By understanding that chickens require REM sleep for health and well-being, animal caretakers can better design housing, routines, and enrichment to meet their full needs—not just for food and water, but for rest and restoration.

What Chicken Sleep Tells Us About Evolution

The presence of REM sleep in chickens also helps scientists understand the evolutionary roots of consciousness. Birds and mammals diverged over 300 million years ago, yet both lineages independently developed complex brains with similar sleep phases. This suggests that REM sleep may have evolved more than once, or that it was already present in a common ancestor.

Either way, the convergence points to its biological value. Studying sleep in birds like chickens can help neuroscientists decode how brain functions evolved—and perhaps gain insight into the basic building blocks of emotion, memory, and consciousness across species.

Conclusion

The humble chicken, often dismissed as ordinary, is in fact a fascinating window into the mysteries of the brain. With their ability to recognize faces, solve problems, and now confirmed to experience REM sleep, chickens stand as a reminder of how much we have yet to learn from the creatures around us.

The next time you see your hens perched quietly at dusk, eyes gently closing, know this: they may be doing something far more complex than resting. They may be dreaming.