500-year-old rock pattern suggests a tree to our subconscious.
The beauty of one of Japan's most popular Zen gardens has long eluded explanation. Now neuroscientists have found that its minimalist design suggests a pleasing picture to our subconcious.
The 500-year-old Ryoanji Temple garden in Kyoto contains five outcroppings of rocks and moss on a rectangle of raked gravel. Using symmetry calculations the researchers have discovered that the objects imply an image of a tree in the empty space between them that we detect, without being aware of doing so1.
The finding suggests that Japanese garden designers - originally priests - "balanced forces from visual science," says study leader Gert Van Tonder of Kyoto University.
The trunk of the hidden branched tree lines up with the preferred garden-viewing spot of ancient temple floorplans, Van Tonder found. Repeating the calculations with random rock groups failed to generate any similar patterns.
Earlier work by Ilona Kovács, a visual scientist at Rutgers University in Piscataway, New Jersey, showed that the human brain uses similar symmetry lines, like those of a child's stick figure, to make sense of shapes2.
"In the Zen garden you have even less to go on with just the best points, or rocks, along the symmetry lines," says Kovács. She suggests the brain may recognize the tree during meditation and other Zen states.
Through the years people have come up with various interpretations for the rock clusters themselves: a mother tiger herding her cubs across a river, mountaintops poking through the clouds, and strokes of Chinese characters.
These logical descriptions miss the point, says Philip Cave, a London-based Japanese garden designer. He thinks the suggestive symmetry explanation fits the Zen mind better.
"It's always been thought that the priest-gardener's layout was something that didn't come from the conscious mind, but from a deeper level," says Cave. "They could have easily intuitively developed that kind of [tree] layout."
The garden, like Mona Lisa's smile, has intrigued visitors for centuries. Tour guides bringing visitors to the 'best' spot to view the garden stop exactly where the symmetry lines converge.
Van Tonder, G., Lyons, M.J. & Ejima, Y. Visual structure of a Japanese Zen garden. Nature, 419, 359, (2002).
Kovács, I. & Julesz, B. Perceptual sensitivity maps within globally defined visual shapes. Nature, 370, 644 - 646 (1994).