Around 50% of people can 'see in the dark,' study shows

When it comes to seeing in the dark, traditional belief is that humans are not able to. However, new research has challenged this, suggesting that at least 50% of all people are able to see the movement of their own hand, even in an environment that is pitch black.

Researchers from the University of Rochester in New York and Vanderbilt University in Tennessee say their findings suggest that what humans normally understand as sight has just as much to do with the brain as it does the eyes.

Duje Tadin, professor of brain and cognitive sciences at the University of Rochester, and Randolph Blake, centennial professor of psychology at Vanderbilt University, say they first discovered that they were able to see their own hand movement in the dark in 2005.

But for the study, published in the journal Psychological Science, the researchers say the challenge was to devise experiments that objectively measured a perception that was subjective.

"While the phenomenon looked real to us, how could we determine if other people were really seeing their own moving hand rather than just telling us what they thought we wanted to hear?," says Prof. Blake.

Kevin Dieter, a postdoctoral fellow at Vanderbilt University, came to their aid as he helped create experiments with the aim of leading the participants to accurately report what they were visualizing.
Experiments under 'false expectations'

The researchers conducted a series of experiments on 129 participants from Rochester, NY, Nashville, TN, Fenton, MI, and Seoul in South Korea.

Some of these participants were chosen because they experience a "blend of senses" in their daily life. They are known as "synesthetes."

The researchers say this means they may see colors when they hear music, or have the ability to experience taste when they hear sounds. For this study, the synesthetes involved were able to see numbers or letters in specific colors.

One experiment required the participants to wear blindfolds that appeared to have lots of holes. The participants were then told they would see "motion under low lighting conditions."

Another experiment required the same participants to wear similar blindfolds without the holes, and the researchers led them to believe they would see nothing.

However, the researchers say that in both experiments, the blindfolds did not have holes and were blocking out all light. The purpose of telling the participants otherwise was to create "false expectations" so they would truly report what they were seeing in the coming experiments.

During these experiments, one of the researchers waved his hand in front of the blindfolded participant, and the participants were also required to move their own hands in front of the blindfolds.