Slime molds’ complex ability to detect mass from a distance

https://www.harvardmagazine.com/2021/11/right-now-can-slime-molds-think

by bangonkeyboard • 5 years ago

99 42 5 years ago

harvardmagazine.com

loa_in_2• 5 years ago

Glass disks could reflect light towards the mold. Otherwise this experiment results seem contradictory to physics.

newsbinator2• 5 years ago

Then, the scientists turned out the lights and watched

loa_in_2• 5 years ago

and watched

They weren't touching, tasting, smelling or hearing.

newsbinator2• 5 years ago

They keep time: if blown with cold air on the first of every hour, by the third hour, they’ll retract just before the cold snap.

Jensson5• 5 years ago

That is super quick learning! And for a formless blob!

Imagine if we knew how to train ML models that could reliably perform feats like this (learn after training, not train to withdraw every hour), while still managing all other parts of being a slime mold like hunting for food, distributing nutrients etc.

voldacar• 5 years ago

Physical slime molds have already been used in an experimental model to optimize road networks:

https://www.sciencedirect.com/science/article/abs/pii/S03032...

otabdeveloper4• 5 years ago

That won't happen for a long time. First we'd need to let go of the idea that "intelligence" means "neural network", and there's a huge amount of ideological resistance to the idea that intelligence isn't made with composeable atomic computation blocks.

krisoft2• 5 years ago

Imagine if we knew how to train ML models that could reliably perform feats like this

I imagined it and I don’t find it that special.

Picking up a strong and regular periodic signal and predicting the next iteration is not a hard problem.

while still managing all other parts of being a slime mold like hunting for food, distributing nutrients etc.

ML models don’t do those things because ML models are abstract constructs without appendages or any other physical embodiment.

We cannot manufacture artifical slime molds because we cannot manufacture artifical cells. This doesn’t seems to be an ML problem. (Or if it is, then everything become an ML problem too and the term lost its meaning.)

rthomas6• 5 years ago

Could it be because the three glass disks cause a slope in the agar gel? And the slime mold prefers to grow downhill?

Darkphibre• 5 years ago

They found that, even more than the total mass of the objects, the slime mold reacted to how much of the horizon the objects occupied. It repeatedly preferred objects spread along the horizon as opposed to those at a single, stacked point

richardfey• 5 years ago

I wonder if it has something to do with surface tension

kseistrup• 5 years ago

Or could evaporation happen faster on the one-disk side so that the slime mold prefers to move towards the more humid/moist side?

123pie123• 5 years ago

Could the slime grow thin extremely small exploratory network first and then decide how to grow its main body?

LegitShady• 5 years ago

How many times was this repeated? How many trials did they have to do before they got this result? How many other objects did they try to see if its something related to the glass?

Jensson5• 5 years ago

How many times was this repeated?

A 100 times for each variant.

How many trials did they have to do before they got this result?

Looks like it picked the side with 3 disks 70% of the time and never picked the side with 1 disk. They tested a ton of different scenarios so the results seems really robust.

"When presented with the 3-discs versus 1-disc choice, the Physarum grew toward the 3 disc regions 70% of the time, while never choosing the 1 disc region alone."

bryan02• 5 years ago

In much the same way that a blindfolded person on a trampoline can sense if other people are on it, TRP channels help the slime mold detect faraway objects.

This is as detailed a description as the article gives in how they detect objects? This explanation does not seem very helpful since I assume the glass disks were not jumping up and down. Is there any more information available on how they sense?

19f191ty• 5 years ago

Sensation of mechanical stimulation. How we sense touch, vibrations, sound.

pphysch• 5 years ago

The experiment happened over a day, so lots of time for environmental vibrations (sound, seismic activity) to paint a subtle picture of the immediate surroundings.

incompatible2• 5 years ago

The original paper seems to be at https://onlinelibrary.wiley.com/doi/10.1002/adma.202008161.

I only glanced at it, but noticed that they hypothesized that the organism uses mechanosensation involving rhythmic pulling on the substrate and interpretation of changes in things like tension, compression or mechanical strain.

adrian_b• 5 years ago

Free access to the (preprint) paper appears to be at:

https://www.researchgate.net/publication/340090261_Mechanose...

guyomes• 5 years ago

An interesting related concept is Mogees [0] that converts any surface to a musical instrument using a contact microphone. The initial underlying theory is described in the thesis of Bruno Zamberlin [1], where he describes in chapter 4 a work with Carmine Emanuele Cella where a piezo sensor is used to convert the vibrations on any physical object into musical sound.

[0] https://youtu.be/xdo8N30qb2A

[1] http://research.gold.ac.uk/id/eprint/12312/

filoeleven• 5 years ago

There’s an iOS app called Impaktor that gives similar results with the phone’s mic instead of a contact mic. So not as nuanced, but great for $5. (You will need headphones.)

https://www.beepstreet.com/ios/impaktor

captn3m0• 5 years ago

I’m curious whether this result contradicts prior findings by making the experimental setups untrustworthy.

If Slime can detect a mass horizon gradient, maybe experiments need to be redesigned to account for it?

Tempest1981• 5 years ago

Nova has a show on this too: https://www.kpbs.org/news/arts-culture/2020/09/15/nova-secre...

SavantIdiot• 5 years ago

Slime molds have three distinct phases. One phase is basically a distributed network of cells that communicate chemically. These signals can indicate when it is time to change form (transform!). Sounds like this is an extension of that in-between form.

There is a fantastic book that talks about this kind of emergent intelligence in slime molds, called--ironically--"Emergence: The Connected Lives of Ants, Brains, Cities, and Software".

The first 1/4 of the book is about the freakiness of slime mold. I thoroughly enjoyed this book, very well written and accessible and covers multiple domains (a lot like G.E.B.); Link to non-amazon:

https://www.barnesandnoble.com/w/emergence-steven-johnson/11...

anotheryou• 5 years ago

Reminds me of the theory that many plants have "eyes".

https://www.scientificamerican.com/article/veggies-with-visi...

https://www.nationalgeographic.com/science/article/the-sneak... (for this there is the claim that it copies plastic plants, too. couldn't find anything factual though)

jcims2• 5 years ago

Object mass wasn’t the only factor the slime mold considered. When the three disks were stacked on top of each other instead of next to each other, the Physarum no longer preferred that side. It grew toward the three-disk and one-disk sides at about the same rate, despite their clear differences in mass. This, Novak says, “was a huge hint, or more like a slap in the face, that it must be basing its decisions on something else, too.”

It's not clear to me if they are using 'mass' as we understand it from physics, or just the general notion of size of an object.

To me the stacking experiment seems to invalidate that its the former. It would probably be useful to do some analysis on airflow inside the petri dish, there could be a very subtle convection and/or radiant heating from the white disks. There's also potential phototropic effects like we would see with plants bending towards light. Both of these inputs would actually be affected by the stacking, where mass is clearly not. (Yes they 'turn off the lights', but you can't take a time lapse movie in absolute darkness)

Regardless of the cause, the effects are going to be extremely subtle, and the fact that the slime mold seems to select a direction based on this incredibly subtle effect is still extremely cool.

Jensson5• 5 years ago

Also it is really cool that it prefers to move towards objects with shapes, it prefers moving towards them over the clean walls and it prefers them more when there are more of those shapes. And the movement is very deliberate, it doesn't just meander in that direction but instead just heads straight to it.

jcims2• 5 years ago

Oh yeah, it definitely picked a direction and committed.

Luc• 5 years ago

Surely mass is a red herring in all this. The masses involved must be waaaaaay too small to detect, especially in the presence of earth's gravity.

Why would a slime mold even evolve this capability of detecting tiny mass differences?

None of it makes sense. It's much more likely there's an ultra-thin tendril they haven't noticed.

Pigalowda2• 5 years ago

There’s a lot of conjecture in this thread so I might as well throw in a couple cents.

Mold is saprophytic so it’s more often than not advantageous to grow toward larger stationary objects in its environment to eat.

The stack of discs deformed the agar gel, the mechanoreceptors on the periphery hyphae detected the tiny deformation and set off a chemical cascade for growth in that direction.

What if the substrate is lumpy and harder than agar? The researchers disabled the mechanoreceptors and there was no “mass detection”. If there’s no deformation in the substrate by discs on a hard bumpy surface then I’m guessing those mechanoreceptors won’t detect the mass.

So mold uses gradient deformation of mechanoreceptors to move toward possible food sources.

geoduck14• 5 years ago

So mold uses gradient deformation of mechanoreceptors to move toward possible food sources.

This explains why they compared the ability to a blind folded person on a trampoline. I wish they had explained it this way.

Pigalowda2• 5 years ago

It’s just my 2 cents.

The mold may not even be moving toward a food source - it could be moving toward the deformation because larger objects cast bigger shadows and it needs to prevent desiccation.

Slime molds’ complex ability to detect mass from a distance

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