The Tell-Tale Brain

asymmetrical ones. The preference likely taps a rule of thumb in the baby’s brain that says, in effect, “Hey, something symmetrical. That feels important. I should keep looking.”

The second evolutionary force is more subtle. By presenting a random sequence of faces with varying degrees of symmetry to college undergraduates (the usual guinea pigs in such experiments), psychologists have found that the most symmetrical faces are generally judged to be the most attractive. This in itself is hardly surprising; no one expects the twisted visage of Quasimodo to be attractive. But intriguingly, even minor deviations are not tolerated. Why?

The surprising answer comes from parasites. Parasitic infestation can profoundly reduce the fertility and fecundity of a potential mate, so evolution places a very high premium on being able to detect whether your mate is infected. If the infestation occurred in early fetal life or infancy, one of the most obvious externally visible signs is a subtle loss of symmetry. Therefore, symmetry is a marker, or flag, for good health, which in turn is an indicator of desirability. This argument explains why your visual system finds symmetry appealing and asymmetry disturbing. It’s an odd thought that so many aspects of evolution—even our aesthetic preferences—are driven by the need to avoid parasites. (I once wrote a satirical essay that “gentlemen prefer blondes” for the same reason. It’s much easier to detect anemia and jaundice caused by parasites in a light-skinned blonde than in a swarthy brunette.)

Of course, this preference for symmetrical mates is largely unconscious. You are completely unaware that you are doing it. What a fitting bit of symmetry that the same evolutionary quirk in the great Mogul emperor Shah Jahan’s brain that caused him to select the perfectly symmetrical, parasite-free face of his beloved Mumtaz, also caused him to construct the exquisitely symmetrical Taj Mahal itself, a universal symbol of eternal love!

But we must now deal with the apparent exceptions. Why is a lack of symmetry appealing at times? Imagine you are arranging furniture, pictures, and other accessories in a room. You don’t need a professional designer to tell you that total symmetry won’t work (although within the room you can have islands of symmetry, such as a rectangular table with symmetrically placed chairs). On the contrary, you need carefully chosen asymmetry to create the most dramatic effects. The clue to resolving this paradox comes from the observation that the symmetry rule applies only to objects, not to large-scale scenes. This makes perfect evolutionary sense because a predator, a prey, a friend, or a mate is always an isolated, independent object.

Your preference for symmetrical objects and asymmetrical scenes is also reflected in the “what” and “how” (sometimes called “where”) streams in your brain’s visual processing stream. The “what” stream (one of two subpathways in the new pathway) flows from your primary visual areas toward your temporal lobes, and concerns itself with discrete objects and the spatial relationships of features within objects, such as the internal proportions of a face. The “how” stream flows from your primary visual area toward your parietal lobes and concerns itself more with your general surroundings and the relationships between objects (such as the distance between you, the gazelle you’re chasing, and the tree it’s about to dodge behind). It’s no surprise that a preference for symmetry is rooted in the “what” stream, where it is needed. So the detection and enjoyment of symmetry is based on object- centered algorithms in your brain, not scene-centered ones. Indeed, objects placed symmetrically in a room would look downright silly because, as we have seen, the brain dislikes coincidences it can’t explain.

Metaphor

The use of metaphor in language is well known, but it’s not widely appreciated that it’s also used extensively in visual art. In Figure 8.4 you see a sandstone sculpture from Kajuraho in Northern India, circa A.D. 1100. The sculpture depicts a voluptuous celestial nymph who arches her back to gaze upward as if aspiring to God or heaven. She probably occupied a niche at the base of a temple. Like most Indian nymphs she has a narrow waist weighed down heavily by big hips and breasts. The arch of the bough over her head closely follows the curvature of her arm (a postural example of a grouping principle called closure). Notice the plump, ripe mangoes dangling from the branch which, like the nymph herself, are a metaphor of the fertility and fecundity of nature. In addition, the plumpness of the mangoes provides a sort of visual echo of the plumpness and ripeness of her breasts. So there are multiple layers of metaphor and meaning in the sculpture, and the result is incredibly beautiful. It’s almost as though the multiple metaphors amplify each other, although why this internal resonance and harmony should be especially pleasing is anybody’s guess.

I find it intriguing that the visual metaphor is probably understood by the right hemisphere long before the more literal-minded left hemisphere can spell out the reasons. (Unlike a lot of flaky pop psychology lore about hemispheric specialization, this particular distinction probably does have a grain of truth.) I am tempted to suggest that there is ordinarily a translation barrier between the left hemisphere’s language-based, propositional logic and the more oneiric (dream like), intuitive “thinking” (if that’s the right word) of the right, and great art sometimes succeeds by dissolving this barrier. How often have you listened to a strain of music that evokes a richness of meaning that is far more subtle than what can be articulated by the philistine left hemisphere?

FIGURE 8.4 A stone nymph below an arching bough, looking heavenward for divine inspiration. Khajuraho, India, eleventh century.

A more mundane example is the use of certain attention-drawing tricks used by designers. The word “tilt” printed in visually tilted letters produces a comical yet pleasing effect. This tempts me to posit a separate law of aesthetics, which we might call “visual resonance,” or “echo” (although I am wary of falling into the trap that some Gestaltists fell into of calling every observation a law). Here the resonance is between the concept of the word “tilt” with its actual literal tilt, blurring the boundary between conception and perception.

In comics, words like “scared,” “fear,” or “shiver” are often printed in wiggly lines as if the letters themselves were trembling. Why is this so effective? I’d say it is because the wiggly line is a spatial echo of your own shiver, which in turn resonates with the concept of fear. It may be that watching someone tremble (or tremble as depicted metaphorically by a wiggly letters) makes you echo the tremble ever so slightly because it prepares you to run away, anticipating the predator that may have caused the other person to tremble. If so, your reaction time for detecting the word “fear” depicted in wiggly letters might be much shorter than if the word were depicted in straight lines (smooth letters), an idea that can be tested in the laboratory.²

I will conclude my comments on the aesthetic law of metaphor with Indian art’s greatest icon: The Dancing Shiva, or Nataraja. In Chennai (Madras), there is bronze gallery in the state museum that houses a magnificent collection of southern Indian bronzes. One of its prize works is a twelfth-century Nataraja (Figure 8.5). One day around the turn of the twentieth century, an elderly firangi (“foreigner” or “white” in Hindi) gentleman was observed gazing at the Nataraja in awe. To the amazement of the museum guards and patrons, he went into a sort of trance and proceeded to mimic the dance postures. A crowd gathered around, but the gentleman seemed oblivious until the curator finally showed up to see what was going on. He almost had the poor man arrested until he realized the European was none other than the world-famous sculptor Auguste Rodin. Rodin was moved to tears by The Dancing Shiva. In his writings he referred to it as one of the greatest works of art ever created by the human mind.

You don’t have to be religious or Indian or Rodin to appreciate the grandeur of this bronze. At a very literal level, it depicts the cosmic dance of Shiva, who creates, sustains, and destroys the Universe. But the sculpture is much more than that; it is a metaphor of the dance of the Universe itself, of the movement and energy of the