People discuss the terrifying moment that bad feeling in their gut proved to be right.

It’s not always physical, rarely conscious; just a strange, sudden sense that something isn’t right. We’ve all felt it at some point in our lives, and thankfully most of the time turns out to be unfounded.

But what about when it’s right?

In an unsettling Reddit thread, people have shared stories of the moment that sense, that feeling, was worth listening to.

Drunk friend, or something more sinister?

“A few years ago, about 1am Sunday morning, I had to take my dog out before bed. I live in a rough neighbourhood and I am a female so I usually have my guard up regardless of the time. Before I left the apartment building, my gut told me something was up,” user calamityhjane wrote.

The street was empty, save for a van parked on the side of the road, and three men.

“Out of the corner of my eye, I could see they were struggling; on closer inspection I see two of the men are holding up the other man between them. I make the assumption that they are headed home after a night of heavy partying and they are just helping their friend get sick or something… Then they notice me and they stop everything and freeze.”

Jane hurried back into her building, unsettled, but her fears forgotten by the next morning. Until…

“There was a notice in the elevator asking for witnesses as to exactly what I saw that evening because a dead body had been found. So… this wasn’t a friend of theirs after all…. they were ditching a body.”

Turn back, now.

It was a typical Thanksgiving for user ManguaHa, sadly. Their parents were arguing, his father yelling about overspending on the holidays.

“It got to a point where my mom told me and my brothers to leave for the party ahead of them,” he wrote. “We didn’t get far from the house until a really bad feeling started sinking in my stomach. I knew my brothers felt something too. I said ‘Can we go back?’ And my older brother turned around immediately. When we got there my father was gone, he had left out of anger and my mum yelled at him to leave. My mother was in her bed, laying still with an empty bottle of sleeping pills beside her.”

Fortunately, she survived.

Listen to the full episode of Mamamia Out Loud here. (Post continues below.)

'I broke into a dead sprint.'

Redditer Miss Predicament noticed a "totally normal-looking" man walking half a block behind after she got off the train. It had happened countess times before on her trip home. Except this time, there was "a feeling".

"Such a bad feeling that, when I turned the corner on my way home, I broke into a dead sprint and hid behind a dumpster in the shadows partway down the street," she wrote. "By the time he came around the corner, I was well hidden, and could see him from my hiding place. As soon as I saw his reaction to the fact that I wasn't there, I knew I had been right to hide. He started LOOKING FOR ME, muttering to himself, he went up and down the street, looked around corners, I hid and held my breath until he was gone. It was terrifying. I am so glad I had that sudden, inexplicable impulse to hide, and listened to it."

'Police told us they suspected she had been dosed.' 

When Canadian Redditer gmoney5786. was in university, he was walking home with his roomate in the early hours of the morning when he came across two men carrying a semi-conscious woman. It looked as if they were helping her, but then, that feeling.

"Our street came up, but instead of turning down it we decided to see what was going on. The guys explained that she was one of their girlfriends and had too much to drink so they were taking her home. We asked them a few more questions: what bar they were at, where she lived, if she was an Ottawa U student etc... They gave pretty convincing answers," he wrote.

Then she dropped her clutch.

"Before they could move, my roommate grabbed the clutch and took out her ID. My roommate then asked if they knew her first and last name along with her birthday. This is where things changed. The other guy got really aggressive and confrontational while the other went silent. They didn't know her name OR birthday. I then pulled out my phone and called police. The guy dropped her and they took off running.

"Police told us they suspected she had been dosed, and that she was lucky we happened to be walking behind her. Pretty scary stuff."

What is that gut feeling? 

That "gut" feeling is difficult even for scientists to fully explain. It's not exactly instinct; that refers to the body’s biological tendency to make one choice over another.

(There are generally only two fears that are considered instinctive: falling, and loud sounds. As Seth Norrholm, a translational neuroscientist at Emory University, explained to CNN, if a sound is loud enough, you'll likely duck. "Loud noises typically means startling. That circuitry is innate," he said. In other words, we're born with it.)

Instead, more intuitive fears - the kind that give you that bad, gut feeling - are learned throughout our lives, and will be triggered based on a collection of beliefs, experiences, and memories.

In both cases - instinctive and intuitive - that fear is designed to protect you from danger, even death. It's an evolutionary survival mechanism that kicks into gear when your senses detect a source of stress. Your brain - specifically an area of the frontal lobes known as the amygdala - is activated, and its energy directed toward avoiding or combating the source of that stress.

As Ohio State University neuropsychiatrist Dr. Katherine Brownlowe told LiveScience, "The release of neurochemicals and hormones causes an increase in heart rate and breathing, shunts blood away from the intestines and sends more to the muscles, for running or fighting."

"It puts all the brain's attention into 'fight-or-flight.'"