Colour awareness has long been a puzzle for researchers in neuroscience and psychology, who debate how much colour observers really perceive.

A new US study probably raises more questions than it answers.

In a series of trials, researchers from Amherst College, MIT and Dartmouth College found that observers routinely failed to notice when colour vanished from the majority of their view. They had surprisingly limited colour perception in their peripheral vision.

Counter-intuitive as it may sound, the study used virtual reality to ensure the participants had a 360-degree, real-world view of the world.

Each wore a head-mounted display fitted with eye-trackers, allowing them to tour historic sites and watch a street dance performance or a symphony orchestra rehearsal simply by turning their heads.

The researchers knew exactly where an observer was looking at all times and could make changes so that only the areas where the person was looking were in colour. Other areas were desaturated, right down to black and white.

But most people didn’t notice. In the most extreme case, almost a third didn’t realise that less than 5% percent of the entire visual field was presented in colour.

While a human’s visual field extends about 210 degrees, which is similar to if your arms are stretched out on your left and right, the study’s results showed that most people’s colour awareness is limited to a small area around the dead centre of their visual field.

In a separate study participants were asked to identify when colour was desaturated in the periphery – and the results were similar. Many people failed to notice when the peripheral colour had been removed.

“We were amazed by how oblivious participants were when colour was removed from up to 95% of their visual world,” says Dartmouth’s Caroline Robertson, senior author of a paper in the journal Proceedings of the National Academy of Sciences.

The obvious question is how this can be. The researchers say they cannot offer a definitive answer but do suggest possibilities worth exploring.

“One possibility is that as observers spend time in an environment, their brains are able to eventually ‘fill-in’ the colour of many items in the periphery,” they write.

“Of course, providing direct evidence for this explanation is challenging since it is extremely difficult to differentiate between scenarios where a subject knows the colour of an object (i.e., ‘I know the tree behind me is green even though I currently cannot see the color green’) from instances where the subject is experiencing the colour of that object online (i.e., ‘I can see the colour green at this very moment’).

“Alternatively, some would argue that there is no need for a filling-in mechanism at all and the intuition of a rich perceptual experience is simply misguided.”

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