Colors of Autumn by Angela Rieck

It’s starting.

Ghost-like mists are rising from the rivers and creeks. Early fall asters and mums are starting to bloom.  Nuts are falling onto the walkways. Desiccated leaves sparsely cover paths.  We have had some blissfully cool mornings.

Everything is pumpkin spiced.

That’s right, crisp fall days are coming. Gorgeous oranges, reds and yellows, the death rattle of dying leaves.  Soon warm coffee drinks will replace ice-cold teas. The loud whining sound of leaf blowers will replace the grinding sound of lawn mowers.

Fruits and vegetable stands will close. Late summer crops will die and dust from harvesting will spray the air.  Eventually frost will be sprinkled over the fields like diamond dust.  Bursts of steam will emerge from horse’s nostrils.

Autumn is coming!

Oh joy.  My least favorite season.

But there is one thing about autumn that I do appreciate–the vivid colors that emerge as the dense humid summer atmosphere gives way to the clear, bright skies of autumn.

I have always loved color. In my early scientific research, I studied human perception because it is just so fascinating, how our senses limit our perception of the physical world.

Humidity dulls our perception of colors because its scatters the sunlight.  Wavelength scattering is very important in our perception of color.  The reason that the sky appears blue is a phenomenon called Rayleigh Scattering.  In simplified terms, small atmospheric particles scatter the shorter, blue wavelengths; allowing us to perceive the sky as blue.  Interestingly, if our cones were more sensitive to shorter wavelengths, the sky would appear violet.

Artists have long maintained that there are places that have more vibrant colors.  The South of France was favored by Impressionists because they believed that the bright, clear air allowed them to see the full color spectrum.  Similarly, many Plein Air artists flock to places in Maine, e.g., Deer Island, that provide similar vividness.  For those looking for the brightest colors, look for places with high altitudes, less pollution and low humidity.

Cone receptors on the back of our retinas allow us to see colors.  We have three types of cones (called trichromacy):

• Short-wave cones for colors with short wavelengths, such as purple and blue.
• Middle-wave cones which are sensitive to medium wavelengths, such as yellow and green.
• Long-wave cones to see colors with long wavelengths, such as red and orange.

In the last decade, scientists have discovered that from 2% to 12% of women have a fourth type of cone receptor, called tetrachromacy. (Because it is an X-linked gene, it is highly unlikely that men could have it.)

In 2010, a woman was documented as having true tetrachromacy. Unlike trichromats who can see up to 1 million colors; tetrachromats can see up to 100 million colors. An artist, Concetta Antico, is a tetrachromat, who paints the world that she sees, and gives us a view into her perceptual world.

Since up to 12% of the women have four cones, why hasn’t it been discovered before?  There are two reasons, first we all perceive the world differently.  How many times have you perceived one color and another person perceived it as a different color?  That is due to both labeling and our perceptual visual system.

The second reason that it hadn’t been discovered is a little more complex.  It is believed that this fourth cone is a mutation of the Long Wave Cone (L).  This mutation can be minor, so the cone responds to similar wavelengths to the unmutated L cone.  In that case, while you would possess the 4th cone your perception would be indistinguishable from the vision of trichromats (3 cones).  If, however, the mutation causes the cone to respond to shorter frequencies (the yellow band); that creates tetrachromacy.

Some insects and birds are tetrachromats (have 4 cones). For example, zebra finches use their four cones to find food and select a mate.

As of yet there is no reliable test for tetrachromacy. Scientists are experimenting with scarf colors…but so far, they have found very few women who have full tetrachromacy.

But at least you know that when the bright clear skies of autumn appear, you know why you enjoy more vivid colors; and perhaps understand why some women may see colors a little differently.

Angela Rieck, a Caroline County native, received her PhD in Mathematical Psychology from the University of Maryland and worked as a scientist at Bell Labs, and other high-tech companies in New Jersey before retiring as a corporate executive. Angela and her dogs divide their time between St Michaels and Key West Florida. Her daughter lives and works in New York City.