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The way we see yellow in summer is different from the way we see yellow in winter, according to a recent study in Current Biology.

Announcing the findings, lead author Lauren Welbourne explained that, "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."

Welbourne and her team asked 67 study participants to identify "unique yellow," a shade which doesn't seem to have any other colors mixed in, on something called a colorimeter in January. The same participants were called back in June to identify the same color again. Most pointed to a yellow with shorter wavelengths as the unique shade.

It's not totally surprising that we interpret color differently as our surroundings change: Consider those color-based optical illusions that make it hard to figure out what color something is:


Slate's Phil Plait explained how this image tricks us into seeing identical shades of color as different:

We perceive the scene as three-dimensional, with the light source to the upper left (note the shadow on the ground). The upper lozenge is shaded so that we see it as tilted away from us at its top (making the bottom look shaded), and the bottom one tilted the opposite way, so its top is lit. That means our brain sees the upper lozenge as lit, while the bottom one is shadowed. That, coupled with the contrasting shading in between them, messes with how our brains interpret the image, and we think the upper one is darker than the bottom one.


So it seems reasonable that the generally, dull, grey backdrop we see in winter would affect our perception of brighter colors.

Still, Welbourne's small study is a first. She says that, "this is the first time natural changes in the environment have been shown to affect our perception of colour." Previous studies have focused largely on how people's visions are different from each other, rather than how the change over time.


Danielle Wiener-Bronner is a news reporter.