Our ability to see the full color spectrum of visible light evolved about 35 million years ago, and it gives us a unique perspective on the world compared with most other mammals.
The evolutionary advantage of color vision may stem from the ability to spot food or predators from long distances, but the ability to see the world in color confers much more than that. Seeing the beauty of the world with trichromatic vision has given us great artworks and is a fundamental part of the human experience for people with healthy vision.
Yet, scientists do not completely understand how we perceive color and what it means to see color.
Is the blue that one person perceives the same as the blue that somebody else sees? How does the perception of color enrich our emotional lives? Is color a property of the world around us or a creation by our brains? These are longstanding questions at the border of philosophy and neuroscience, which continue to fascinate researchers around the world.
A study that the journal PNAS recently published reports on an exciting new investigation of color vision, asking the question: How much color do we really see?
The study, which is the result of a collaboration between Dartmouth College in New Hampshire and Amherst College in Massachusetts, reveals that we see much less color than we think we do. Human awareness of color in the periphery is surprisingly limited, with the brain “filling in” the rest, the researchers say.
As we go about our daily lives, we get the impression of a rich and colorful world all around us, but whether this feeling is an accurate representation of what we really perceive has come into question.
Recent studies, for example, suggest that awareness is limited, especially in the periphery. Peripheral vision occurs away from the center of gaze, which covers approximately the same area as a person’s arm span.
However, there is still much debate around whether this is due to limits either in perception or in how much of a scene we can pay attention to and later remember.
To help to resolve this debate, the new study used virtual reality (VR) to mimic what it is really like to see color in the world. The researchers used head-mounted VR displays with eye trackers to monitor the participants’ eye movements while they navigated a 360-degree real-world environment.
The virtual environments included tours of historical sites, a street dance performance, and a symphony rehearsal. While the participants were exploring these scenes, the researchers removed the color in the environment outside of where they were directly looking.
A video demonstrating what the trials looked like is available to view here.
In total, 160 people took part in the first part of the study, which involved five trials. In the first four trials, the virtual visual world appeared in full color, and the researchers encouraged the participants to explore it for 20 seconds.
In the fifth trial, the central visual field remained in full color, but peripheral color gradually disappeared over a 5-second interval until the periphery was in grayscale.
The researchers were surprised to discover that the participants were often unaware when most of the visual world lacked color.
When the largest colored region was present, the overwhelming majority of people failed to notice the lack of color in the rest of the environment.
In the most extreme case, when only a 10-degree region of color was present (equivalent to a circle with a radius of 10 centimeters at arm’s length and less than 5% of the entire visual field) almost one-third of people failed to notice.
“We were amazed by how oblivious participants were when color was removed from up to 95% of their visual world,” says senior author Prof. Caroline Robertson.
In a second study, the team asked a smaller number of participants (20 people) to look out for a loss of color in the periphery and press a button as soon as they noticed the desaturation occurring.
The results showed that participants generally did not notice the loss of color beyond a circular region of 37.5 degrees around their gaze point (meaning that two-thirds of the visual world was in black and white), even when they knew to look for it.
“Our results show that our intuitive sense of a rich, colorful visual world is largely incorrect. Our brain is likely filling in much of our perceptual experience.”
– Prof. Caroline Robertson
As there is no known anatomical limit at this range, the results indicate that even when people are actively looking for color changes in the periphery, they tend to miss them.
This research demonstrates that people can improve their sensitivity to color in the periphery of their vision by paying attention.
However, overall, the findings suggest that most people’s color awareness is limited to a relatively small area at the center of their visual field. The brain fills in the rest, the authors say, based on predictions of which colors are most likely to be present.
This adds weight to the notion that neuroscientists, perhaps most notably Anil Seth, are putting forward — namely, that our perception of reality is based largely on what the brain “expects” us to see. It may be, therefore, a cleverly weaved network of predictions informed by what we know to be true from our past experiences.
