Seasons influence how human eye perceives color, study shows

© Romeo Ranoco
The human eye’s perception of colors varies between seasons, a new study has revealed. The color yellow, for instance, appears greener to humans during the summer.

Researchers from the University of York have cast new light on how humans process various colors in different seasons.

The psychological study found that the color yellow appears to look greener in the summer months.

Human beings identify four unique hues – blue, green, yellow and red – which do not contain mixtures of any other color.

The study, published in Current Biology, found ‘unique yellow’ particularly interesting because it is perceived the same across large populations. Everybody agrees on what the color looks like even though people’s eyes are different.

The researchers were curious to find out why the color is so stable and what factors could possibly change it.

Initially, they thought unique yellow might depend on the color of the natural world rather than the biology of the eye.

Lead author and PhD student Lauren Welbourne said she found between seasons “our vision adapts to changes in the environment.”

“So in summer when there is a much larger amount of foliage, our visual system has to account for the fact that on average we are exposed to far more green,” she said.

“In York, you typically have grey, dull winters and then in summer you have greenery everywhere,” she added.

A human’s vision compensates for those changes and “surprisingly changes what we think ‘yellow’ looks like.”

“It’s a bit like changing the color balance on your TV.”

Scientists tested 67 men and women in January and June. The participants were placed in a dark room.

Using a machine called a colorimeter, participants were asked to adjust a dial backward and forward until they felt they had found unique yellow – with no hint of a green or red.

June volunteers adjusted more green out of yellow than those in January. The study proved their eyes were processing the colors differently.

Welbourne said this is the first time natural changes in the environment have been shown to effect on perception of color.

“Although there’s no disorder that this can fix, the more we learn about how vision and color in particular is processed, the better we can understand exactly how we see the world.”