The quirk behind the burning need to pee when we hear rainstorms, waterfalls and babbling brooks seems to be all tied up in the power of suggestion.
Most of you are familiar with the name Pavlov, and know that he had something to do with dogs. That something is an experiment where the Russian doctor showed that autonomic responses (visceral reflexes that occur automatically and unconsciously under the control of the autonomic nervous system) could be triggered by outside stimuli. Dog owners will attest that when a pooch gets its mouth on a piece of meat, they usually produce a river of saliva. In his experiment, Pavlov give dogs some meat powder, which caused them to salivate, right after ringing a bell. After months of repetition, he was able to ring the bell without any meat powder in sight, and the dogs would salivate because they’d been conditioned to associate the bell with food. For another example of classical conditioning in action, see this clip from The Office.
Pavlov thought that a lot of this automatic and unconscious learning happens all the time to people, and you can probably think of a few cases from your own life where you reflexively react a certain way to a seemingly unrelated stimulus. Having to pee at the sound of running water appears to be the same sort of conditioned response. The sound of running water not only mimics the sound of urination itself to create a Pavlovianassociation, but flushing and washing one’s hands also produce that same sound and are closely associated with urinating and further strengthen the connection.