Somewhere along the line we got the idea that taking naps would interrupt sleep cycles–that if you had a little snooze in the middle of that day, you wouldn’t be able to stay asleep at night. Not true, say the experts. In fact, catching some daytime Zs may actually make you smarter.

Researchers at Weill Cornell Medical College in White Plains, N.Y., monitored a group of adults 50-83. After some initial baselines, half were instructed to take a 45-minute nap every day, the other half to take a two-hour nap every day.

The results? Those in the short-nap group increased their total sleep time by an average of 20 minutes, while those in the long-nap group increased theirs by an average of 65 minutes. Neither group reported that their night-time sleep was interrupted in any way.

In addition, “Napping increased the time spent in slow-wave and rapid-eye-movement (REM) sleep, which are thought to play important roles in restoring the body and brain. Whether they took long naps or short naps, participants showed significant improvement on three of the four tests in the study’s cognitive-assessment battery.”

Bottom line: Naps increase the quality of your sleep at night and improve brain function during the day.