There’s a certain temperature, time of day and ambient noise that could make Bob want to take a nap, to crawl away somewhere and sleep. He thought it had to do with his days as a child in L.A., when he would be outside in the back yard on a sunny day, and he would feel a small breeze and hear a rare type of plane overhead.

It wasn’t a jet, it was some sort of propeller plane. He never found out what kind it was, but it had a unique sound, and his sense memory always triggered a relaxed feeling whenever he heard it as an adult.

He always hoped he wouldn’t hear it while he was driving a car, in case he decided to take a nap on the interstate. It was a pretty vivid stimulus-response thing, and he loved when it happened. Life had gotten so complicated as an adult, and whenever he heard that sound he could go back to being relaxed again for a couple minutes.

He thought about trying to find out what kind of plane it was, but he decided that would just ruin his response to it. Better to simply enjoy it, he said.