November 1, 2014
6 min read
The facts and fictions of crimson perception
By Susana Martinez-Conde & Stephen L. Macknik
Red is a powerful color. It's the color of Cupid and the Devil, the color of love and hate. It brings to mind hot-blooded anger and Scarlet Letter shame. It means luck in China, where bridal wear is red, mourning in parts of Africa and sex in Amsterdam's red-light district.
Some of the hue's significance has a biological basis. Many humans get red in the face from increased blood flow when they are angry. A similar process activates a flush of embarrassment or a more flirtatious blush. Seeing red also triggers some surprising behaviors. For instance, drivers blocked in traffic by a red car react faster and more aggressively than drivers barred by vehicles of other colors.
Perhaps the most famous example of the pigment's power comes from animal perception. For hundreds of years matadors have taunted bulls by flashing a red cape. According to bullfighting lore, the color choice is said to help hide bloodstains, but it may have other advantages. Whereas humans are trichromats—meaning that we have three types of retinal cones sensitive to long (red), medium (green) and short (blue) wavelengths—cattle are dichromats: they possess only two kinds of cones.
Perceptual measurements indicate that cattle can discriminate red from green and blue but not green and blue from each other. Moreover, researchers have found that cattle are more active and aroused in red light than in blue or green light. Another study reported that although fighting bulls may charge all sorts of moving objects, the charges carry greater force when directed against warm colors such as red.
In the 1960s the late Spanish-born neuroscientist José M. R. Delgado, then at Yale University, pitted the lure of the red matador's cape against the power of direct brain stimulation by testing whether electronic brain implants could stop a charging bull in its tracks. With the implants linked to a remote control, Delgado climbed into an arena in Córdoba, Spain, and enraged the bull with his cape. His move was a bold one: if Delgado's idea to directly stimulate the caudate nucleus, an area involved in voluntary motion, failed, he would pay the ultimate price. The bull charged—¡Olé!—but Delgado remembered to mash the remote's button in the nick of time, stopping the toro mid-charge. Even if red has the power to lure a bull to attack, little, if anything, can beat direct brain stimulation.
As the examples that follow illustrate, red regularly sways behavior. Charged with social and cultural meanings, it is a powerful enhancer, sending signals that may not really reflect an entity's true nature.
