Have you ever known you were dreaming while you were dreaming? According to WebMD, about 50 percent of people have had this experience, which is known as lucid dreaming. Now, a study suggests that a phone app can help boost the chances of having a lucid dream.

Researchers at Northwestern University in Illinois built an app that they hoped would encourage lucid dreaming. App users are instructed to listen to a particular sound, such as several beeps, before bed and try to associate the sound with an awareness of their own mind and body. The app then repeats that sound six hours later, while the user is sleeping. The goal is to get the user back into a state of self-awareness so that they come to know when they are dreaming. 

The researchers tested the app on a group of 19 people. They asked the group how many lucid dreams they’d experienced in the previous week and found there was an average of 0.74 lucid dreams. The researchers then asked the 19 participants to use the app every night for one week and found the average number of lucid dreams increased to 2.11.

“That’s a really big increase for lucid dreaming,” Northwestern cognitive neuroscientist Karen Konkoly told Science News. “Lucid dreaming once a week is a lot.”

To test whether the app was responsible for the increased number of lucid dreams, the researchers gathered 112 people for another experiment. All 112 people were asked to listen to certain app sounds before bed. For one night, the app played these same sounds for everyone in the group while they were sleeping. But the next night, only 40 people heard these sounds. Thirty-five people heard different sounds while sleeping, and another 37 heard no sounds.

On the first night, 17 percent of the group had lucid dreams. On the second night, only 5 percent of the people who didn’t hear the before-bed sounds said they had lucid dreams. This suggests that the sounds people hear and practice with before bed can help train their brains to have a lucid dream when they hear the same sounds while sleeping. In other words, the app might work!