The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

Some contrast combinations are more pleasing to the eye than others. For example, high-contrast colors such as a blue splotch on a yellow background are more attention grabbing than low-contrast pairings like a yellow splotch on an orange background. It’s puzzling at first glance. After all, you can easily see a yellow object against an orange background but that combination does not draw your attention the same way as blue on yellow.

The reason a boundary of high color contrast is more attention getting can be traced to our primate origins, to when we swung arm over arm like Spiderman in the unruly treetops, in dim twilight or across great distances. Many fruits are red on green so our primate eyes will see them. The plants advertise themselves so animals and birds can spot them from a great distance, knowing they are ripe and ready to eat and be dispersed through defecation of the seeds. If trees on Mars were mainly yellow, we would expect to see blue fruits.

The law of contrast—juxtaposing dissimilar colors and/or luminances—might seem to contradict the law of grouping, which involves connecting similar or identical colors. And yet the evolutionary function of both principles is, broadly speaking, the same: to delineate and direct attention to object boundaries. In nature, both laws help species survive. Their main difference lies in the area over which the comparison or integration of colors occurs. Contrast detection involves comparing regions of color that lie right next to each other in visual space. This makes evolutionary sense because object boundaries usually coincide with contrasting luminance or color. Grouping, on the other hand, performs comparisons over wider distances. Its goal is to detect an object that is partially obscured, like a lion hiding behind a bush. Glue those yellow patches together perceptually, and it turns out to be one big lump shaped like a lion.

In modern times we harness contrast and grouping to serve novel purposes unrelated to their original survival function. For example, a good fashion designer will emphasize the salience of an edge by using dissimilar, highly contrasting colors (contrast), but will use similar colors for far-flung regions (grouping). As I mentioned in Chapter 7, red shoes go with a red shirt (conducive to grouping). It’s true, of course, that the red shoes aren’t an innate part of the red shirt, but the designer is tapping into the principle that, in your evolutionary past, they would have belonged to a single object. But vermilion scarf on a ruby-red shirt is hideous. Too much low contrast. Yet a high-contrast blue scarf on a red shirt will work fine, and it’s even better if the blue is flecked with red polka dots or floral prints.

Similarly, an abstract artist will use a more abstract form of the law of contrast to capture your attention. The San Diego Museum of Contemporary Art has in its contemporary art collection a large cube about three feet in diameter, densely covered with tiny metal needles pointing in random directions (by Tara Donovan). The sculpture resembles fur made of shining metal. Several violations of expectations are at work here. Large metal cubes usually have smooth surfaces but this one is furry. Cubes are inorganic while fur is organic. Fur is usually a natural brown or white, and is soft to touch, not metallic and prickly. These shocking conceptual contrasts endlessly titillate your attention.

Indian artists use a similar trick in their sculptures of voluptuous nymphs. The nymph is naked except for a few strings of very ornate coarsely textured jewelry draped on her (or flying off her chest if she is dancing). The baroque jewelry contrasts sharply with her body, making her bare skin look even more smooth and sensuous.

Isolation

Earlier I suggested that art involves creating images that produce heightened activation of visual areas in your brain and emotions associated with visual images. Yet any artist will tell you that a simple outline or doodle—say, Picasso’s doves or Rodin’s sketches of nudes—can be much more effective than a full color photo of the same object. The artist emphasizes a single source of information—such as color, form, or motion—and deliberately plays down or deletes other sources. I call this the “law of isolation.”

Again we have an apparent contradiction. Earlier I emphasized peak shift—hyperbole and exaggeration in art—but now I am emphasizing understatement. Aren’t the two ideas polar opposites? How can less be more? The answer: They aim to achieve different goals.