Sleep is a fascinating part of life, and we spend a significant amount of time doing it—about one-third of our lives, in fact! Since it’s such a big part of our daily routine, here are five unusual facts about sleep you might not know.

1. Dreams Might Be a Form of Mental Practice

Not in the mystical sense, but your brain actually uses dreams to process new experiences, skills, and emotions. Far from resting, your brain is highly active during sleep, especially in the REM (rapid-eye movement) stage. Brain scans show complex activity during this phase, where your mind creates vivid dreams to help you work through problems and emotions, almost like a safe rehearsal for real life.

2. Falling Asleep Too Fast Could Mean You’re Sleep Deprived

While falling asleep quickly might feel like a blessing, it can also signal that you’re not getting enough rest. Ideally, it should take about 10-15 minutes to drift off, showing that you’re tired but not overly exhausted. On the flip side, if it takes more than 20 minutes to fall asleep, it’s better to get out of bed and relax elsewhere until you feel sleepy again—just avoid screens or stimulating activities that could keep you awake longer.

3. Some Animals Sleep Half Their Brain at a Time

Unlike humans, some animals like fish, birds, and marine mammals sleep with only one hemisphere of their brain at a time. This allows them to stay alert to predators, continue swimming for oxygen, or even fly during migration. In birds, for example, scientists have found that they can sleep with one eye open, corresponding to the side of the brain that’s still awake!

4. Sleep Positions Don’t Reveal Your Personality

Though it’s a common claim that your sleeping position reflects your personality (like curling up in the fetal position means you’re tough on the outside but soft inside), this is actually a myth. The idea originated from an informal survey by a hotel chain, not scientific research. So, your sleep position probably doesn’t say much about you—other than whether your mattress is uncomfortable. If it’s time for a new one, consider checking out TempurPedic mattresses, known for their comfort and 10-year warranty.

5. We Still Don’t Know Why We Sleep

Despite extensive research, the exact reason we sleep remains a mystery. While the consequences of not sleeping—like hallucinations, memory loss, and even death—are well-documented, the evolutionary purpose is still debated. We do know that nearly every animal sleeps, even simple creatures like fruit flies, and that sleep deprivation quickly impacts decision-making and learning. So while we may not fully understand why we sleep, it’s clear that we need it!