You know that queasy feeling you get in your gut when walking alone in a dark, abandoned parking lot? Chances are, that’s not a nervousness you can logic away. When it comes to innate anxiety and how you react to it, the brain is less in charge than we like to think.
A long, electrified cable snakes up from your abdomen, past your heart, lungs and esophagus, all the way to your brain stem. It’s called the vagus nerve, and it’s the telephone line between brain and gut, providing two-way communication. Recently, some researchers at ETH Zurich wanted to see what would happen if they made it a one-way conversation. They cut the vagal afferents in a bunch of rats, taking away the stomach’s ability to send messages to the brain, and placed their subjects in the rat’s version of a dark, abandoned parking lot—a bright open space.
It became clear that the rats with the severed afferent nerve were less visibly scared than the control rats. But they weren’t fearless.
In a conditioning experiment, the rats learned to link a neutral acoustic stimulus – a sound – to an unpleasant experience. Here, the signal path between the stomach and brain appeared to play no role, with the test animals learning the association as well as the control animals. If, however, the researchers switched from a negative to a neutral stimulus, the rats without gut instinct required significantly longer to associate the sound with the new, neutral situation.
Not all fears work the same way. But if your gut is telling to you to hightail it out of some threatening situation—maybe it's better to just listen. Even if you can convince yourself to stay, that gut-clenching fear isn't going away.