Chapter 11:   The Finer Arts             from

MACHINERY of THE MIND: Inside the New Science of Artificial Intelligence

       As Harold Cohen recalls it, his fascination with American Indian petroglyphs began in 1973, when, in a canyon in northern California, he stood gazing at a wall of rock and the pictures some long-dead artist had chisled there.    Twelve years later, Cohen, an artist who uses computers to explore the mysteries of creativity, is still struck by the memory of what he saw:

       "This extraordinary sight - an escarpment rising from the floor of the desert, so you had a wall about fifteen feet high that formed a kind of arc about a hundred feet across."   It looked, Cohen remembers, like a theater, hewn by nature from the side of a cliff.   Onstage were a number of petroglyphs, the ancient, primitive drawings that adorn rocks throughout the southwestern United States.

       Some petroglyphs, which range in age from 500 to 15,000 years old, are fairly easy to interpret.  The lines of the simple figures form crude images of birds, deer, human faces.  But the most mysterious of these symbols are far more abstract: roughly drawn circles, ovals, squares, and triangles; some empty, some filled with parallel lines, crosses, grids, et cetera; spirals, zigzags, targets made of concentric circles, circles linked like beads, circles surrounded by radiating lines.  The petroglyphs are usually fairly small, maybe several inches from end to end. The patterns Cohen saw that day in northern California were especially intriguing because of their size.

       "They were much bigger than average - I mean something like six feet across.   The placing was very deliberate and very dramatic.   It gave a very strong sense of having been done for something.   There was a sense of purposefulness about the thing that impressed me enormously."   And so, as it did when confronted witha work of art, Cohen's mind began, almost automatically, to search for meaning.

      Usually, when we see art, we can assume we have some things in common with the artist.   We know something of his culture and history.   Faced with a thousand-year-old painting we know that the man hanging on the cross is meant to be Jesus.   We can look at a Mexican carving of a creature, half bird, half serpent, and be fairly sure we are seeing a replica of the Aztec god Quetzalcoatl.   In both cases, we can interpret the image because information about the artist's culture has survived along with the art.  Or, as Cohen likes to put it, the"codebook" the artist used to encrypt a message into the lines and colors of a painting, or the grooves in a piece of rock, has been handed down to us through the centuries.   If the artist's culture is not too different from our own, we already know what the symbols stand for, what the artwork is supposed to mean - the codebook is in our heads. Otherwise, we can look in a library.

       But as he stared at the petroglyphs, Cohen realized he was faced with a very different situation.   "I was struck by the fact that I really had no idea who these people were."   He had no way of knowing what the artist might have felt and thought, or what life had been like in those days.   The symbols Cohen was trying to decipher were from a culture that had disappeared long ago, leaving no record, no history.   The codebook had been lost forever. There was no way to know what the artist had intended by these strange patterns.


           And yet Cohen still felt that familiar compulsion to interpret.   It was obvious that there was intelligence in those marks, that they had been put there by a human.   Over the years, the content of the message may have been lost, the information dissipated through time.   But merely by virtue of their form it was clear that the marks were intentional, that they were the product of a mind.   And, since another mind - Harold Cohen's was trying to read them, a certain resonance was generated, a connection that extended across the centuries.  These were images in their most raw and basic form, stripped of all the cultural trappings that say this means this, and that means that. What remained were just lines on rock. Why then did they have such evocative power?

      This feeling of a connection with an ancient intelligence was almost mystical, and many people would have been content to leave it at that. But Cohen was interested in more rational explanations. For about a year he had been studying as a visiting scholar at Stanford University's artificial-intelligence lab. Incongruously,perhaps, his experience with the petroglyphs gave him an idea for how he might strip the process of imagemaking to its bare essentials and program a computer to create.

      Since his early days as a painter, Cohen, a stout, heavy-set man with a graying beard and short ponytail, has strongly believed in the importance of demystifying art. From 1952 to 1968 he worked in his native England, creating abstract paintings that explored, among many other things, the way color and shape can be used to induce in the minds of an audience a whole range of aesthetic effects. In the words of Michael C. Compton, keeper of museum services for the Tate Gallery in London,  "Harold Cohen built up a reputation as a painter equal to that of any British artist of his generation."  He won scholarships and fellowships; his work was displayed in shows all over the world; he had paintings in the Tate's permanent collection, one-person shows in prestigious galleries.  "In short," Compton wrote, "he was a successful painter and could look forward to a long and rewarding career."

     Yet he was different from many of his colleagues in that, for him, art making was an analytical process, a means of systematically exploring what he called "the mechanics and processes of communication." As he worked he introspected, trying to see what the procedures were that he used to make images that seemed to move people in certain ways. As Compton describes the paintings, they sound almost like scientific experiments: