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Some samples of slime molds, in petri dishes, were on display outside of the panel. We do not know if they have any names, at this time, but they are more intelligent than you'd think. Photo taken by Mitchell S. Lampert.


[WSF19] ‘Expanding Intellect Beyond Humans,’ Part 2: Intelligence without Brains

Or: ‘How a slime mold can win at cards’

Brian Greene’s annual World Science Festival hit Manhattan again last week, and AiPT! Science was there! Keep coming back all week for more coverage!

This year’s World Science Festival led two panels which attempted to expand what it means to be intelligent, including one that discussed intelligence in other animals. The second got even weirder, titled “Intelligence without Brains,” which took place the evening of June 1, 2019.

This panel was moderated by Natalie Angier, a Pulitzer prize-winning science columnist for The New York Times, and author. It opened with a short film assuring us that the 1970s fad of talking to plants, popularized by the book The Secret Life of Plants by Peter Tompkins and Christopher Bird, turned out to be complete pseudoscience. But do some current scientists still think that plants can think?

Left to right: Mark Moffett, Naomi Leonard, Simon Garnier, Thomas Horton, Monica Gagliano, and moderator Natalie Angier. Photo by Mitchell S. Lampert.

Many mediums of transmitters

We think of a basic unit of an intelligent system as a neuro-transmitter. Panelist Monica Gagliano pointed out this implies, “If you don’t have neurons, you don’t have a transmitter.” Why can’t intelligence emerge from other types of transmitters?

In a time-lapse video, two separate bean stalks were shown competing for the use of a pole to wrap themselves around on. When one became the winner, the other seemed to give up and search for something else to latch onto. How did the loser plant know this, without ever touching the other plant, nor the pole? Something functioned as if it were a “neuro-transmitter,” but we’re unsure exactly what that is.

Monica Gagliano, a research associate professor based in the University of Sydney, figured out that bio-acoustics could be part of the answer. Plants make noise, and can hear other plants! She discovered this by conducting experiments on chili plants, which grow and respond differently when they are planted near basil, a “good” neighboring plant, and fennel, a “bad” plant.

Gagliano systematically cut off all the usual suspects for transmission between them: light, chemicals, and touch. However, the reactions to the other plants were still the same. She then looked more at the roots, and hypothesized they were making vibrations in the soil that could be picked up by other plants. Using very sensitive microphones, she was able to record these sounds. Of course, everyone else was initially skeptical, but her findings were eventually published, and are starting to be accepted.

The smarts of slime molds

Simon Garnier, associate professor in the Federated Department of Biology at the New Jersey Institute of Technology and head of its Swarm Lab, spoke about slime molds. They’re neither plant, nor animal, nor fungus. And yet, experiments show they can win against a laboratory “casino” in a Monte Carlo type of game, which had been previously used to test intelligence in pigeons and other animals. They’re able to use proteins as primitive forms of muscles to make decisions, as they often know if they’ve landed on something “nice” or not.

Slime molds in petri dishes. Photo by Mitchell S. Lampert.

Another weird thing about slime molds is that if you cut one in half, they’ll function as two separate entities, and if you merge them back together, they function as a single entity again. An experiment was done where one batch of the stuff was trained to cross a salt bridge to some food, an achievement that took some effort, as slime molds are very averse to salt.

But once the trained batch was connected to an untrained one, that new batch was able to learn to cross the salt bridge much more quickly. Something is transmitting knowledge among molecules of slime mold, and some of these findings can help us understand how our own brains learn.

Slime molds can also naturally create networks of paths across landscapes that are as optimized as any engineer would have calculated, and one can automatically find the shortest route out of a maze, all by itself. However, Garnier hesitates to call any of this “intelligence,” preferring the more generic “problem solving” in his formal work.

Fungus networks among us

The third panel member, Thomas Horton, is a professor of mycology at the State University of New York College of Environmental Science and Forestry. He demonstrated that mycorrhizal fungus actually search for the nutrients it needs, and can even hone in on fresh spots as they are injected into new soil sites. We don’t actually know how it does this.

We also see evidence of fungal networks sharing information and resources between each other. They’ll even cooperate with multiple other species of fungus and plants, if they don’t directly compete for their same resource base. We now know that when a plant is being chewed on by an insect, it sends signals to other plants, which will then prepare them to defend themselves better. It appears as though the mycelium fungal networks are what provides that transfer — if they’re cut, the alerts don’t happen.

Gagliano also conducted an experiment with Mimosa pudica, a plant that instantly responds to touch, to see if it retains memories of its encounters. She placed one pot of the plant into a device that would drop it several feet, without any actual damage being done to it.

On the first drop, they would close up, but, after two or three more, they wouldn’t anymore. They’d learned this fall wasn’t a threat. She then tested the plants’ memory of this training, and found it would be retained for at least a month, assuming the environment didn’t otherwise change much. If the lighting conditions were altered, for example, the memory would not last as long, and it would close up again on a new drop. We still don’t know understand how this memory system works.

Mimosa Pudica is one of the few plant species that physically reacts to threats on our time scales. On the left, we can see that as you touch the leaves, they instantly close up. On the right is the result of lots of people touching the plant at once — the whole plant closes up into an unappetizing-looking thing. Photos by Mitchell S. Lampert at Epcot Center in Walt Disney World.

Farms and swarms

Biologist Mark Moffett, who studied under E.O. Wilson, claimed that leafcutter ants behave a lot more like humans than chimps do! They farm and cultivate a fungus that they get their full nutrition from, which required solving many of the same problems we humans have, like building highways, manufacturing their own herbicides and pesticides, defending themselves with large and “dumb” soldiers, and even collecting and disposing of garbage. And they achieve all this without a leader, because they’re genetic clones, though they do have diversified body types, each with a highly specialized skill.

Naomi Leonard, the Edwin S. Wilsey Professor of Mechanical and Aerospace Engineering at Princeton University, has been working with swarms of robots to collect data about our oceans. A lot of her research was influenced by the flying patterns of starlings. Experiments have shown that each individual bird only pays attention to about  six or seven other members in its swarm, a number even independent mathematical models seem to recognize as optimal. There can be a lot of variability in how each individual behaves in the wild, but the overall emergent behavior can still be observed.

Environmental scientist Thomas Horton brought up the complex subject of tree canopy biology. One example of fascinating tree movement is that of philodendrons, a type of vine. When a bird drops a philodendron seed on the ground, it will automatically move to the closest tree, where it will begin to grow up the trunk. At the same time it grows upwards, its tail end withers away.

The result in time-lapse photography is that it appears to move much “like a snake” crawling up a tree. When it reaches the top of the canopy, it will reach out to try to cross over to another tree. If it fails, it will fall to the ground, and simply crawl up the nearest trunk, to try again.

Horton further warned about trees that have been known to strangle each other. Don’t stand between them for very long periods of time!


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