January 26, 2010
Slime Mold Proves to Be a Brainy Blob
By HENRY FOUNTAIN
Let’s hear it for slime molds.
Researchers in Japan have shown that a slime mold can design a network that is as efficient as one developed by humans over many years: the Tokyo rail system. Furthermore, the slime mold can build its network in a day.
A slime mold is what scientists refer to as a single-celled amoeboid organism. When foraging for food, it spreads out as an amorphous mass and then builds tubular connections between the food sources.
It may be just a blob, but it is a smart one. “We’ve found an unexpected high ability of information processing in this organism,” said Toshiyuki Nakagaki, a researcher at Hokkaido University who has long studied slime molds.
“I wanted to pose a complicated program to this slime mold, to design a large network,” Dr. Nakagaki said. “This kind of program is not so easy, even for humans.”
So he and his colleagues set up an experiment where they laid out 36 bits of food in a pattern corresponding to cities in the Tokyo area and put a slime mold, Physarum polycephalum, at the spot corresponding to Tokyo.
As they report in Science, after 26 hours the slime mold had created a series of tubular connections that matched, to a great extent, the rail links among these cities. The researchers found that the slime mold network was as efficient as the rail network, it tolerated breaks in the connections just as well, and it was created at reasonable cost to the organism.
Of course, a series of small tubes is far different from a large network of rails. “But behind the differences there is a common principle from a math point of view,” Dr. Nakagaki said. Using the slime mold’s performance as a guide, the researchers created a mathematical model that they say may help people design other networks, like those used in mobile communications.