January 14, 2014
Study Helps Debunk Existence Of A ‘Sixth Sense’
Brett Smith for redOrbit.com - Your Universe Online
A new study from two psychologists at the University of Melbourne has shown that the human mind can perceive change in an environment without knowing exactly what has changed. Lead researcher Piers Howe interpreted his findings as evidence against the existence of extrasensory perception (ESP), also known as a sixth sense.“There is a common belief that observers can experience changes directly with their mind, without needing to rely on the traditional physical senses such as vision, hearing, taste, smell and touch to identify it,” Howe said. “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.”
In their report, which was published in the open-access journal PLOS ONE, the Australian researchers attributed this ability to perceive change to the brain being overwhelmed by visual statistics – essentially the idea that the brain ‘realized’ a change, but could not process the nature of it. The study team said this realization is often misinterpreted as a gut feeling or sixth sense.
To reach their conclusion, the researchers presented ten participants with two portrait photographs on a black background, both of the same female individual. Each image was presented individually for 1.5 seconds with a 1 second blank interval between the two images. After the second photo was shown, the participant was asked if a change had occurred from the first image to the second – such as a new hairstyle. If they said yes, they were asked to correctly identify the change. Each volunteer performed 140 trials.
Instances where a participant said they sensed a change but could not identify it were called “only-sense” trials. However, Howe, writing in The Conversation about the study, pointed out a flaw in the design of this experiment: What if a participant were to randomly guess that a change had occurred?
“In order to estimate how many only-sense trials could be expected due to guessing, we incorporated ‘catch trials’ in which no change occurred,” he wrote. “By measuring the fraction of catch trials on which the participant reported a change, we could estimate the number of only-sense trials that could be generated by guessing in the trials where a change actually occurred.”
Howe added that other trials in the study provided more details behind this type of change perception.
“We showed that if the change between photos did not alter the ‘scene statistics’ – for instance by a change in the total amount of red or green in the scene – our participants were, without fail, able to identify any changes that they sensed,” he wrote.
“Conversely, when the change altered the ‘visual statistics’ of the scene, participants could reliably sense changes that they could not identify,” he continued. “For example, if the subject of the photograph changed her hair color from brown to red, the participant might unconsciously detect this overall increase in redness, but mistakenly think lipstick color changed.”
“Our study therefore shows that people can indeed detect changes that they cannot identify, but debunks the claim that this is evidence for a sixth sense,” Howe concluded.