“Between the expressions of laughter and weeping there is no difference in the motion of the features,” Leonardo da Vinci wrote in his posthumously published Treatise on Painting, “either in the eyes, mouth or cheeks.” With the difference between the physical expression of emotions so subtle, artists had a challenge on their hands: How to differentially depict, in the words of Sir Joshua Reynolds, the “frantic joy of a Bacchante and the grief of a Mary Magdalen”?

To do so, artists relied on a staged iconography of expression and posture, codified in handbooks. (…) Despite such expert guidance in the depiction of laughter, in the history of art there are very few images of people laughing. (…)

Nearly half a millennium after Leonardo, contemporary scientists have discovered a neurological explanation for the affinity between physical expressions and emotional sensations of joy and grief. In the centuries between, scientists took over where artists left off in urgently pursuing the question. Charles Darwin notably fused the two approaches, using the art of photography to further his scientific inquiry. (…) He hoped to use photography to portray emotional subtleties ” like the close similarity between the laughing and crying face ” with a renewed realism.

Capturing particular expressions, inherently transitory, volatile, and ephemeral, at first seemed almost impossible with the long exposure time photography then required. (…) Darwin described the spasms a laughing fit provoked, which would have rendered any photograph a blur: “During excessive laughter the whole body is often thrown backward and shakes, or is almost convulsed. The respiration is much disturbed; the head and face become gorged with blood, with the veins distended; and the orbicular muscles are spasmodically contracted in order to protect the eyes. Tears are freely shed,” he noted, appending a key observation, “Hence . . . it is scarcely possible to point out any difference between the tear-stained face of a person after a paroxysm of excessive laughter and after a bitter crying-fit”.

Darwin found a ready-made solution to the problem of how to capture raw expression in a set of extraordinary pictures taken by the French doctor Guillaume Duchenne de Boulogne and reproduced in his book, Mécanismes de la physiognomie humaine (1862). Duchenne practiced medicine at the Salpêtrière hospital, where he embarked on an infamous series of experiments in an effort to explain the workings of facial musculature. His process involved administering a constant flow of electric current to human facial muscles, which contorted the face into various expressions and held them long enough for photographs to be taken. (…)

Five years ago, at the Salpêtrière hospital in Paris, where Duchenne had distorted faces with a galvanized rod, Professor Yves Agid implanted an electrode into the brain of a 65-year-old woman in the hope of discovering a cure for her Parkinson’s disease. The electric current would sometimes alleviate her symptoms, but this time something quite unexpected happened. A melancholy expression came over the patient, her head slumped forward, and she tilted to the right. She began sobbing uncontrollably. (…) With another flick of the switch her dark mood was immediately lifted. She smiled and said apologetically, “What was all that about?”

In Los Angeles, California, around the same time, another surgeon, Itzhak Fried, inserted the tip of an electrode into the skull of a 16-year-old girl to investigate her severe case of epilepsy. When a low voltage was applied she began to smile. As it increased she started giggling, until finally she fell about in paroxysms of laughter. “You guys are just so funny,” she guffawed at the team of scientists in white lab coats, who began to crack up too because her laughter was contagious.

By poking about in this adolescent girl’s head, neuroscientists had discovered, by mistake, what they called the “laughter center,” a piece of the brain roughly one inch square, in which our sense of humor seems to be located.

{ Cabinet magazine | Continue reading }

READ MORE >> science | August 15th, 2008