The world of living things

For Daniel Dennett a key realization of the Darwinian revolution is 'competence without comprehension.' [1] Some forms of intelligence do not require consciousness as we normally think of it. [2]

Darwin touches on this matter. "Some animals extremely low in the scale apparently display a certain amount of reason," he wrote after extensive study of earthworms; "a result which has surprised me more than anything else in regard to worms." [3]

The study of cognition and the capacity to process information has come a long way and been substantially rethought since Darwin's time. Still, he would surely be intrigued that intelligence of a kind may be present in even 'simpler' life forms than the earth-worm. [4] As an article in New Scientist this week reminds us, it's been a decade since Toshiyuki Nakagaki reported that the slime mold Physarum polycephalum can negotiate a maze to reach food at the exit. This, Nakagaki wrote, "implies that cellular materials can show a primitive intelligence". [5] He is, however:

unwilling to extend the notion of intelligence to an oil droplet recently observed 'solving' a maze. "It is nonsense for me to consider intelligence in non-living systems," he says.

Should we then draw a definite a line between living beings and the non-living world? NS reports a different tack from the philosopher Andy Clark, who says much of biology boils down to chemistry:

"The mere fact that it's just physical stuff doing what it does can't be a strike against the droplets. Whatever intelligence is, it can't be intelligent all the way down. It's just dumb stuff at the bottom."

...The droplet appears to be moving in an intelligent way because the aqueous environment surrounding the droplet is structured to such a high degree by the pH gradient that it makes the dumb droplet appear smart. "It's a neat demonstration of just how much problem-solving punch you can get from a minimal internal structure in a nicely enabling environment," says Clark

Humans rely on the same trick, says Clark. It forms the basis of the extended mind theory proposed by Clark and David Chalmers in the late 1990s. This holds that the division between mind and environment is less rigid than previously thought; the mind uses information within the environment as an extension of itself.


Footnotes

[1] See, for example Darwin's "strange inversion of reasoning" (2009)

[2] And neither do some forms of memory. For a very short introduction see Memories in Nature by Olivia Judson (2009)

[3] The Formation of Vegetable Mould through the Action of Worms (1881). E. O. Wilson and others have arguably done for ants what Darwin did for earthworms. For example:

Even with a brain one-millionth the size of a human’s, an ant can learn a simple maze half as fast as a laboratory rat, and remember the directions to as many as five different destinations when she forages away from the nest. After exploring a new terrain, a worker can integrate all the seemingly haphazard twists and loops she made and, amazingly, return to the nest in a straight line.

[4] In Created from Animals: The moral implications of Darwinism (1990), James Rachels notes:

"The mental powers of worms"? It sounds like a joke. ...It should be noted, however, that Darwin's brief in behalf of worms was not part of some general campaign to attribute intelligence to all creatures, no matter how lowly. He was far too cautious for that. He regarded the matter as an open question, to be decided experimentally in each case. Darwin observed that other lowly animals do not show the same degree of intelligence as the worm.

[5] Intelligence: Maze-solving by an amoeboid organism (2000). More recently Nakagaki and his colleagues have shown that a slime mold can quickly build a network as complex as the Tokyo metro system. Rules for Biologically Inspired Adaptive Network Design (2010)


Image: (Teaching a stone to talk) Newgrange

Mind the many-headed slime

Somehow, this single-celled organism [Physarum polycephalum] had memorised the pattern of events it was faced with and changed its behaviour to anticipate a future event. That's something we humans have trouble enough with, let alone a single-celled organism without a neuron to call its own.

... [Max] Di Ventra speculates that the viscosities of the sol and gel components of the slime mould make for a mechanical analogue of memristance. When the external temperature rises, the gel component starts to break down and become less viscous, creating new pathways through which the sol can flow and speeding up the cell's movement. A lowered temperature reverses that process, but how the initial state is regained depends on where the pathways were formed, and therefore on the cell's internal history.

In true memristive fashion, [Leon] Chua had anticipated the idea that memristors might have something to say about how biological organisms learn. While completing his first paper on memristors, he became fascinated by synapses - the gaps between nerve cells in higher organisms across which nerve impulses must pass. In particular, he noticed their complex electrical response to the ebb and flow of potassium and sodium ions across the membranes of each cell, which allow the synapses to alter their response according to the frequency and strength of signals. It looked maddeningly similar to the response a memristor would produce. "I realised then that synapses were memristors," he says. "The ion channel was the missing circuit element I was looking for, and it already existed in nature."

-- Slime mold to DARPA: Justin Mullins on the future of artificial intelligence.

In The Social Amoeboe: The Biology of Cellular Slime Molds, John Tyler Bonner concludes:

We can see the beginning of an era of enlightenment for slime molds...the day may come where we may hail Alan Turing, along with his other claims to fame as the Robert MacArthur of developmental biology...[but] we still have a long -- and interesting way to go. And the reason we all started working on cellular slime molds is that they were supposed to be so simple!

Social slime

the discovery is much more than a mere curiosity, because the colony consists of what are known as social amoebas. Only an apparent oxymoron, social amoebas are able to gather in organized groups and behave cooperatively, some even committing suicide to help fellow amoebas reproduce. The discovery of such a huge colony of genetically identical amoebas provides insight into how such cooperation and sociality might have evolved and may help to explain why microbes are being found to show social behaviors more often than was expected.

-- Oozing Through Texas Soil, a Team of Amoebas Billions Strong