Ever feel a creepy, tingling sensation that you ‘just know’ something is different? Well, it’s not a sixth sense, a pair of scientists say -- it’s just your conscious mind failing to catch up with your perception.

In a new paper published in the journal PLoS ONE, Australian researchers say they’ve found evidence to help debunk the idea of extra-sensory perception (ESP), or a “sixth sense.”

“Although reports of a sixth sense are common in lay writings and popular culture, the scientific evidence for this has been ambiguous,” University of Melbourne psychologists Piers Howe and Margaret Webb wrote in an article on their research for The Conversation. “This might be due to experiment participants having a tendency to claim to have seen a change even when they are unsure, giving the false impression that they are able to sense changes when they cannot.”

To try and flush out any sign of a sixth sense, Howe and Webb performed several experiments showing people pairs of color photographs, each showing the same woman. In some pairs, there was no real difference between the photos, but in others, the subject had made a small change. She might be wearing earrings or a hat in one photo that weren’t worn in the other, or she might be wearing two different hairstyles.

Each photograph was shown to study participants for just 1.5 seconds, with a 1 second break between photos. After each pair of photographs, the participant was first asked whether there was a difference between the photos, and then asked to identify what that change was by picking from a list of options. Participants looked at 140 pairs of photos overall. The scientists also performed follow-up experiments with pairs of photos showing simple shapes, sometimes shown in different colors.

Howe and Webb found that while people could generally identify that there was a change between two photos in a pair, they could not say exactly what was the change.

“We were able to show that while observers could reliably sense changes that they could not visually identify, this ability was not due to extrasensory perception or a sixth sense,” Howe said in a statement.

Is this truly debunking ESP? There’s still much about human perception that seems to verge on the fantastic -- just last year, scientists untangled the web of neurons that allows our brains to quickly estimate groups of numbers (e.g., “this book is probably about 500 pages long,” or “there are about 30 fries on my plate”). This number sense, formally called subitizing, seems to center on two groups of neurons located just above each ear.

But Howe and Webb are hardly the first scientists to rain on psychics’ parades. Harvard scientists in 2008 tried to look for the existence of ESP using a brain scanning experiment. Participants were directly shown some photographs while they were inside an MRI scanner, but other photographs were presented in ways designed to be sensed only through ESP. Photographs were either shown to another person -- the participant’s friend, relative, or significant other -- or on a computer outside the participants’ field of vision. Other pictures were shown to the participant much later.

If the participants really were able to read minds, see things outside of their normal field of vision, or perceive the future, the brain scan should have shown different patterns between those ESP-based stimuli and the direct visual stimuli. But the researchers basically found no change in the brain.

“We didn’t find anything, but we didn’t find anything in an interesting way,” researcher Samuel Moulton told the Harvard Crimson at the time.

SOURCE: Howe, Piers and Margaret Webb. “Detecting unidentified changes.” PLoS ONE published 13 January, 2014.