A fascinating post. Regarding the discussion on sentience, I think we would benefit from thinking more in terms of a continuum. The world is not black and white. Without going as far as an extreme view like panpsychism, the Darwinian adage natura non facit saltum probably applies to the gradation of sentience across life forms.
Flagellates like E. coli appear capable of arbitrating a “choice” between approaching or moving away from a region depending on whether it contains more nutrients or repellents (motivated trade-off, somewhat like in Cabanac’s theory ?). From what I understand, this “behavior” (chemotaxis) relies on a type of chemical summation, amplification mechanisms through catalysis, and a capacity to return to equilibrium (robustness or homeostasis of Turing-type reaction-diffusion networks).
In protists like paramecia, we find a similar capacity to arbitrate “choices” in movement based on the environment, but this appears to rely on a more complex, faster, and more efficient electrochemical computation system that can be seen as a precursor to what happens within a neuron. Then we move to a small neural network in the worm (as discussed in the article), to the insect, to the fish, to the rat, and to the human.
I am very skeptical of the idea that there could be an unambiguous tipping point between all these levels. By definition, evolution is evolutionary, relatively continuous (even if there can be punctuated equilibria and phases of acceleration). Natural selection tinkers with what exists, stacking layers of complexity. The emergence of a higher-level system does not eliminate lower levels but builds upon them.
This is certainly why simply having the connectome of a worm is insufficient to simulate it satisfactorily. It’s not the only relevant level. This connectome does not exist completely independently of lower levels. We must not forget the essential mechanism of signal amplification in all these nested systems.
When I look at the Milky Way or the Magellanic Cloud with the naked eye in the dark of night, I’m operating at the limit of my light sensitivity, in fact, at the limits of physics, since retinal rods are sensitive to a single photon. The signal is amplified by a cascade of chemical reactions by a factor of approximately 10^6. My brain is slightly less sensitive since it takes several amplified photons before I begin to perceive something. But that’s still extremely little. A few elementary particles representing zero mass and infinitesimal momentum energy are enough to trigger an entire cascade of computations that can significantly influence my behavior.
Vision may be an extreme example, but it should inspire humility. All five senses are examples where amplification plays a major role. A very low-level signal gets amplified, filtered, protected from noise, and propagates to high-level systems, to consciousness in humans. It’s difficult to exclude the possibility of other circuits descending to the lowest levels of intracellular computation.
Until recently, I readily imagined the brain as a kind of small biological computer. Now my framework is to see each cell as a microscopic computer. Most cells in the body would be rather like home PCs, weakly connected. In contrast, neurons would be comparable to the machines composing datacenters, highly performant and hyper-connected. Computation, cognition, or sentience would be present at all levels but to varying degrees depending on the computing power of the network segment under consideration (computing power closely linked to connectivity).In sum, something quite reminiscent of Dehaene’s global workspace theory and Tononi’s integrated information theory (I admit that, like Scott Alexander, I’ve never quite grasped how these theories oppose each other, as they seem rather complementary to me).
A fascinating post. Regarding the discussion on sentience, I think we would benefit from thinking more in terms of a continuum. The world is not black and white. Without going as far as an extreme view like panpsychism, the Darwinian adage natura non facit saltum probably applies to the gradation of sentience across life forms.
Flagellates like E. coli appear capable of arbitrating a “choice” between approaching or moving away from a region depending on whether it contains more nutrients or repellents (motivated trade-off, somewhat like in Cabanac’s theory ?). From what I understand, this “behavior” (chemotaxis) relies on a type of chemical summation, amplification mechanisms through catalysis, and a capacity to return to equilibrium (robustness or homeostasis of Turing-type reaction-diffusion networks).
In protists like paramecia, we find a similar capacity to arbitrate “choices” in movement based on the environment, but this appears to rely on a more complex, faster, and more efficient electrochemical computation system that can be seen as a precursor to what happens within a neuron. Then we move to a small neural network in the worm (as discussed in the article), to the insect, to the fish, to the rat, and to the human.
I am very skeptical of the idea that there could be an unambiguous tipping point between all these levels. By definition, evolution is evolutionary, relatively continuous (even if there can be punctuated equilibria and phases of acceleration). Natural selection tinkers with what exists, stacking layers of complexity. The emergence of a higher-level system does not eliminate lower levels but builds upon them.
This is certainly why simply having the connectome of a worm is insufficient to simulate it satisfactorily. It’s not the only relevant level. This connectome does not exist completely independently of lower levels. We must not forget the essential mechanism of signal amplification in all these nested systems.
When I look at the Milky Way or the Magellanic Cloud with the naked eye in the dark of night, I’m operating at the limit of my light sensitivity, in fact, at the limits of physics, since retinal rods are sensitive to a single photon. The signal is amplified by a cascade of chemical reactions by a factor of approximately 10^6. My brain is slightly less sensitive since it takes several amplified photons before I begin to perceive something. But that’s still extremely little. A few elementary particles representing zero mass and infinitesimal momentum energy are enough to trigger an entire cascade of computations that can significantly influence my behavior.
Vision may be an extreme example, but it should inspire humility. All five senses are examples where amplification plays a major role. A very low-level signal gets amplified, filtered, protected from noise, and propagates to high-level systems, to consciousness in humans. It’s difficult to exclude the possibility of other circuits descending to the lowest levels of intracellular computation.
Until recently, I readily imagined the brain as a kind of small biological computer. Now my framework is to see each cell as a microscopic computer. Most cells in the body would be rather like home PCs, weakly connected. In contrast, neurons would be comparable to the machines composing datacenters, highly performant and hyper-connected. Computation, cognition, or sentience would be present at all levels but to varying degrees depending on the computing power of the network segment under consideration (computing power closely linked to connectivity).In sum, something quite reminiscent of Dehaene’s global workspace theory and Tononi’s integrated information theory (I admit that, like Scott Alexander, I’ve never quite grasped how these theories oppose each other, as they seem rather complementary to me).