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The headline from a recent article in ScienceDaily caught my eye: Birds perceive ‘warm’ colors differently from ‘cool’ ones. Understanding and seeing color temperature can be a major stumbling block for artists. And now birds understand it? I wanted to know more. So after reading the article in ScienceDaily, I found another previous article in Nature, and then the original Duke University study more appropriately titled “Categorical perception of colour signals in a songbird”. This was probably way too much information, but I thought there must be a nugget of information that was relevant to understanding the perception of color and color temperature.

Warmer and cooler colors fall into two general categories: red, orange, yellow as warmer; and blue, green, violet as cooler. The pedestrian explanation is that we associate red, orange, yellow with fire, etc. and the cooler colors with ice and snow. That’s obviously a very messy explanation, but it is one based on how language can affect our ability to recognize and categorize color. Infants, however, can discriminate between basic color categories before they have learned the words for colors, so the idea that color perception is entirely based on culture and language does not tell the whole story. 

Zebra finches, photo by Michael Lawton

Here’s where the birds (zebra finches) come in. While birds are pretty good with singing, they are not known for their language skills or for their use of fire to get warm. They do, however, have impressive color discrimination abilities and, unlike humans, can perceive the ultraviolet range of the color spectrum. It turns out they can also perceive colors in distinct categories, such as the shift from red to orange.

Now you might be thinking that seeing the difference between red and orange is not such a big deal. That’s because we think there are color separations within the visual spectrum of light and we also have words for these separations. We perceive a distinct difference between orange and red when, in fact, the colors are part of a range of wavelengths of light that seamlessly merge from one color to another. Red becomes orange, then yellow, green turns to blue and then violet. But we are actually more inclined to see the boundary separating colors, the most obvious difference, than the variations within the color range.  Why does this happen?

The answer is categorical perception. Categorical perception occurs when items that range along a continuum are perceived as being either more or less similar to each other than they really are.   Humans, primates, and now, according to this study, birds are all more sensitive to the differences between colors than to the similarities. The bird study reinforces the idea that color categories are more than arbitrary subdivisions of the spectrum based on the words we use to describe them. 

It turned out that describing birds as perceiving warm and cool colors was merely a categorical description of the colors used in the study and not an accurate description of the research. So no, birds do not recognize color temperature.  Describing colors as warmer or cooler is most likely limited to human perception and human language. And despite the words having no scientific pedigree and sometimes confusing ambiguity, they do help to describe and categorize the millions of color variations we are capable of seeing.  

While the bird study provides evidence for a biological basis for color perception, we can’t ignore the language bias that alters our perceptions. Warm-cool color, for example, suggests an absolute value, when in fact color temperature is a relative value. Warmer-cooler is a more accurate description for comparing color differences. Similarly, labeling a banana as yellow, or a tree trunk as brown limits our perceptional ability to discriminate color variation.

Categorizing is a useful and necessary tool for simplifying information and it’s helpful to understand that visual processing defaults to basic categorization. We should be able to use this knowledge to look for similarities and relationships instead of just differences, and to try and see beyond the obvious.