It learns, remembers, solves problems, and chooses the healthiest item on the menu; and yet it doesn’t have a brain. The slime mold, also known as the SpongeBob SquarePants—yellow Physarum Polycephalum, is a mold that is not actually a mold. It is an amoeba and exists as a single-celled organism that joins together with other cells to form a mass network-like super cell. Since scientists say that it has been around for at least over 600 million years, the slime mold has been used in countless laboratories to study the evolution of simple processes that organisms exhibited even before they developed brains. However, when the slime mold began to display a primitive form of intelligent behavior, scientists were forced to rethink intelligence in a pared back, holistic way. Scientist Chris Reid of the University of Sydney, who has conducted countless experiments on the slime mold, said that “slime molds are redefining what you need to have to qualify as intelligent.”
Much of the slime mold’s action was actually documented when an artist, Heather Barnett, received a petri dish of slime mold from her microbiologist friend with the sole instruction to “play with it.” Along with a tip-off that slime mold favors oats over any kind of food, she turned to time-lapse photography in order to capture her observations.
Initially, she observed that after feeding on a pile of oats, the slime mold went off to explore new territories in different directions simultaneously. However, when it met itself, it recognized that it was there and retreated back, heading in new directions. Thus, she concluded, slime mold can map its territory; know itself, as if with seeming intention.
What looks like clump of fluorescent slime has actually provided the basis for numerous scientific studies and research papers. For example, a team at the Hokkaido University in Japan filled a maze with slime mold, planting two oats at separate locations in the maze. They found that the slime mold formed a connection between the food, retracting from empty areas, and establishing, time and time again, the shortest possible route between the oats. These researchers concluded that slime mold had a primitive form of intelligence.
Another study exposed the slime mold to blasts of cold air at a set of time intervals. Since the slime mold thrives in dark, damp, and humid environments, it naturally disliked the cold and slowed its own growth in response to the air blasts. After four repeated blasts of cold air, the researchers stopped the blasts. The slime mold, however, in anticipation of the next blast, slowed down its growth, despite the lack of cold air being blown onto it. Somehow, as if classically conditioned, it knew that it was time for the cold air; and thus, provided the scientists with the conclusion that the slime mold was able to learn.
A third and truly fascinating experiment was performed in which the slime mold was placed on a railway map of the Tokyo transit system, with oats positioned at the different stations in major cities and suburbs. In just 26 hours, the mold fanned out in a branching pattern, forming a network between all of the different oats that almost identically simulated the existing train tracks that had been developed over a course of one hundred years by community dwellers, civil engineers, and urban planners. In just over a day, the slime mold had mapped the same efficient network between stations, forming along the quickest routes.
So the question is, how does this organism operate? Without a central nervous system, without a brain—how can it perform behaviors that we associate with brain function?
World over, teams of researchers are working to decode the slime mold’s biological principles to uncover the origin of its intelligence. In pursuit of answering this very question, Barnett filmed the mold at 100 times magnification. She saw that within the mold was a rhythmic, pulsing flow carrying cellular material, nutrients, and chemical information throughout the cell network, pulsating in one direction, then back in another, forming a synchronous and continuous oscillation within the cell. The rhythmic motion of its cytoplasm is what scientists believe to be the basis for the complex understanding of the mold in its environment, even without a central control center. It is within these oscillations that Reid’s believes its intelligence—its primitive spatial memory and internal clock—lies.
Thus, the ancient slime mold, lacking a nervous system, is a smashing success in the hall of fame of evolution; instead of blindly oozing from one place to another, it explores its environment with acumen, seeks efficiency, and shrewdly chooses conditions most amenable to its own survival. As an alternative to brain-based intelligence, you might even say that this little creature has broken the mold.