How to Get Showers of Ideas

I lunched today with a well-known quantum physicist, who mentioned that about half his ideas, and most of his best ones, happen in the shower. I asked him whether he knew why.

Being a physicist, he has developed a model to explain why. It goes, loosely, as follows:

1) There is an unconscious part of the mind that processes things without our knowing it, and in fact while our conscious mind is doing its thing.

2) Ideas are either algorithmic, like working through a differential equation, or non-algorithmic, which means they get worked out more or less randomly.

So why does one get ideas in the morning? He cautions that he's not a biologist, but he guesses that during the day, we need to concentrate on doing what we need to do to not get eaten by lions. So we have evolved strong biological systems to keep our unconscious mind from distracting us, so that we can't run away from the lion. In short, our conscious minds are insulated from the unconscious part of our mind, perhaps by some kind of gatekeeper in the brain.

We need a certain amount of sleep, and the unconscious mind must also be kept away during that time, as well. But in the morning, in the nice, warm, safe shower, the brain's gatekeeper says, 'okay, now's a good time to toss out those ideas you've been working on.'
I looked around for some other theories on getting ideas in the shower.

• Why your best ideas come in the shower noted that many people also get ideas during period of metnal free association, like when they're exercising.
• Thinking in the shower treats the shower as womb-like (kind of), which evokes a sense of comfort that allows us to come up with ideas.
• A Perfect Brainstorm, by my fellow contributor at Inc. magazine, Alison Stein Wellner, examines better ways to get ideas while not in the shower. And it includes this sidebar on why ideas do come in the shower

• Ideas lost in the shower
• Writing in the shower
• zany ideas that increase writing productivity and quality