We have all had the experience where we can't recall something or we get stuck on a problem and as soon as we stop thinking about it, we remember it or the answer pops into our head.

The break from trying to think about it is what helps us remember or see the solution. Researchers call that break an "incubation period."

Research can't tell us exactly how incubation periods work, but it can give us some clues.

Benedict Carey, author of How We Learn: The Surprising Truth of When, Where, and Why It Happens sheds some light on what we know.

Carey identifies three success conditions for when an incubation period is most likely to lead to an aha moment.

1. You have to reach an impasse.

To gain the benefits of an incubation period, you can't just take a break whenever you feel like one. You have to work until you reach a point where you are truly stuck. You have to work until you've exhausted your options.

2. Look for opportunities to break fixed assumptions.

We often get stuck because we only look at a problem one way. Taking a break often leads to a fresh perspective, which helps us see something we didn't notice the first time.

For example, Carey describes one study where Karl Duncker, a German psychologist, asked participants to use a variety of supplies to attach a birthday candle to a wall in a way that would allow it to be safely lit. The supplies included candles, matches, a box of thumb tacks, among other items.

Most participants struggled to come up with a solution.

However, the researchers tried another variation. For some of the participants the thumb tacks were emptied out on the table, leaving the empty box on its own. This helped the participants see that the box itself could be tacked to the wall and used as a support for the candle.

Why did this group perform differently? Separating the thumb tacks from the box helped the participants see that the box was an item on it's own that could be used. For the group who saw the thumb tacks inside the box, they fixated on the box as a container for the thumb tacks and weren't able to see it that it could serve another purpose. Duncker argued that the box was "functionally fixed."

It's this fixation on one path that often leads to us getting stuck. An incubation period can help alleviate our fixation.

3. Keep an eye out for environmental cues.

Aha moments often happen when we see something in our environment that triggers a memory or the insight itself.

Norman Meier, a psychologist at the University of Michigan, conducted another puzzle-based experiment where he brought participants into a room with two hanging ropes and asked them to tie the ends of the ropes together. There was only one challenge, the ropes were far enough apart that the participant couldn't reach both ends of the ropes at the same time.

The solution involved swinging one rope like a pendulum so that it could be reached from the other rope. But many participants struggled to see this insight. Meier introduced a break--an incubation period--into the experiment at which point he intentionally brushed against one of the ropes causing it to swing. This subtle environmental cue was enough to help the participants to see the insight.

So while researchers can't tell us exactly how to create those magical aha moments, we can increase the likelihood of them by:

  1. Working until we reach an impasse.
  2. Looking for opportunities to break fixed assumptions.
  3. Keeping an eye out for environmental cues.