Yellow is the loudest colour

At a recent Toronto Blue Jays baseball game, my son pointed out the many police officers on the field of Rogers Stadium. Our seats were high and their dark uniforms blended well with blue outfield walls so my aging eyes had overlooked them. He was right: the field was discretely crawling with cops. 

While exiting the stadium a little later, the same hidden cops were suddenly omnipresent amidst the jubilant home crowd. The change? They were wearing bright yellow jackets. Same cops. On the field, they were invisible in dark uniforms. Afterwards, they screamed their presence in high-visibility electric yellow coats. A fine example of clothing dictating civic order.

Yellow. The colour of rubber ducks, sunflowers, school buses, French cycling champs, life jackets and police warning tape. Often sunny and cheerful. Sometimes sickly and off-putting. But always loud and unmissable.

What is it about yellow?

In his Theory of Colours (1810), Wolfgang Goethe called yellow “light that has been dampened by darkness" (as opposed to blue, which is darkness weakened by light). Contrary to Newton and other colour theorists of the day, Goethe insisted darkness wasn’t the absence of light, but an active ingredient with light that combined to make all the colours of the rainbow. To him, when yellow moves toward red, becoming "red-yellow" (orange), this was due to an increase of energy and light, akin to a growing fire. Tycho Brahe in 1572, observing a yellow supernova brighten to orange in the Scandinavian night sky would likely have agreed.

Side bar: Tycho Brahe wore a prosthetic nose for most of this adult life after his cousin sliced off his real nose in a drunken duel over who was the better mathematician. I’m sure there’s a lesson somewhere in all that awesomeness but I’ll be buggered if I can find it.

Speaking of geniuses with bits chopped off, Vincent Van Gogh is probably the painter most closely associated with yellow. Sunflowers, Cafe Terrace At Night, The Yellow House, all masterpieces that show-off his devotion to yellow paint. To Van Gogh, yellow reigned supreme among the colours as a divine life force, a belief borne from his delirious year going steadily mad staring at the southern French sun. He captured the sun’s vitality with a brand new canary yellow pigment called "Chrome Yellow", created by adding wildly carcinogenic lead chromate powder to oil. 

It bears noting that his captivation with yellow may have also been due to undiagnosed xanthopsia which, if he indeed suffered from it, would have saturated everything he looked at with yellow tinges. Nevertheless, he loved the stuff so much he even painted his house yellow and it would still be there had the Americans not dropped a bomb on it in 1944. Yet another way that yellow is hard to miss.

But why is it so hard to miss? Why does it visually pop more than all the other colours?

The human eye.

Most of us know the basic physics and anatomy of human sight. Light enters the eye through an opening (the iris), gets refracted through a rubbery lens, slices through the gelatinous interior of the eye before bouncing off the retina, a densely knitted sheet of photoreceptive neurons called rods and cones. From there, the optic nerve transports that information to the brain to develop into images and voila - we can see.

Rods and cones.

Cones register colour and visual detail in well-lit situations. Rods can only see black-and-white but are great for movement and light contrast, especially in dim environments. This is where it gets interesting. Almost all the cones are found in the 2mm center of the retina called the fovea. As Canadian researcher Colin Ellard describes it “hold your thumb out at arm’s length. Look at it. Your thumb fills the fovea.” Foveal vision is focused vision. It’s what we mean when we talk about vision. Reading. Watching TV. Recognizing a face. Picking out colours. All that is the work of the cones in the fovea.

The rest is rods. Rows and rows of black-and-white rods. And this area, 99% of the eye, is what we call the peripheral vision. Think about that for a moment. Our vision is almost all peripheral vision.

Peripheral vision is our visual radar system. Great at telling you something is coming, but lousy at telling you what it is, unless it’s in black and white. In fact, the peripheral system is so bad at detecting colour that the brain  has to ‘outpaint’ colour based on information it receives from the fovea. In other words, most of what we see, we see as bright shapes of black-and-white to which our brain adds colour after the fact. It also transmits information to the brain much faster than the fovea and to a different part of the brain. Foveal information goes to analytical parts of the brain for high-level processing. Peripheral information bypasses all that and goes straight to the amygdala - the seat of emotions and fight-or-flight responses.

Read that again.

Peripheral visual information is felt before it’s understood. This is where Immersive comes in. As we’ve talked about in other posts, the Immersive effect is a feeling. Taken a little further, if you want to deepen the Immersive Effect, start designing for the peripheral system.

In a recent paper in Nature, Dutch researchers David Terburg and Sjoerd Stuitt say that we process emotional expressions—specifically fear and anger—faster in our peripheral vision than in our central gaze. In Haunted Houses, you don't just see the monster in the corner; you feel the danger before you turn your head. Clearly, Immersive and peripheral vision go hand-in-glove.

Side bar: An intriguing aspect of Immersion is the connection between peripheral vision and our sense of balance (the Vestibular System). When visual elements like a horizon line move too quickly up or down a wall, audiences can feel a kind of vertigo often called “‘Simulator Sickness”. It turns out, our brain has evolved a reflex to connect peripheral vision with the inner ear and you feel woozy when there’s a discrepancy between the two. I guess it makes sense they’d be connected but I do wish this connection didn’t induce nausea. If you’ve ever mopped-up audience vomit off of LEDs then I suspect you feel the same.

Answering the yellow question.

In the fovea are three different types of cones: “S”, "M" and “L”, for Short, Medium and Long light wavelengths. S-cones detect blue light and only make up 10% of our eye. M-cones (red) and L-cones (green) comprise the rest and yellow light triggers them both.  Only yellow light.

This is the key.

The brain receives double the signal from yellow light than it does from any of the other colours. In fact, our photoreceptor cones have evolved to be most sensitive and send the strongest signal when they receive wavelengths around 555 nanometers. And what colour is 555 nanometers?

Bright lime-yellow.

Exactly what cops wear after a Blue Jays game. 

Side bar: The jury is still out on why the human eye has evolved to be particularly sensitive to yellow light, but it likely has something to do with visible sunlight, which also comes in at around 500 nanometers.

So, it turns out yellow is the "loudest" color because to our eyes yellow isn't a color. Yellow is the mathematical maximum of the L and M cone response. It's particularly eye-catching and "bright" because our peripheral system registers it as a light patch and our brain amplifies this light patch with the most intense biological signal the human eye can generate.

Yellow...who knew?

Maria Vukota is a 4th year Psychology student at Toronto Metropolitan University and once spent a thankless summer researching peripheral vision for the lab. And this was pre-AI. She's a trouper and deserves all the success coming her way.