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I honestly don't get the brain-to-body size argument. Why should a larger organism need more brain size to control his larger body? A large engine often do not

I honestly don't get the brain-to-body size argument. Why should a larger organism need more brain size to control his larger body? A large engine often do not require more inputs than a small one and I don't understand why this shouldn't also be the case for organs.

dbspin 4y ago
Because the engine analogy though intuitively appealing, doesn't accurately map onto the way organisms work. The 'nerves' which send control and sensory information to and from our organs are neurons. The 'extended brain' includes the central and peripheral nervous systems, and takes part in local and distributed cognition. So it's not a case of an engine running a machine, or a CPU controlling the information flowing from a bunch of subsystems. The neurocognitive architecture is spread across the body. Naturally more cerebral cortex is needed to perform higher order processing and control the signalling throughout the whales enormous nervous system.
- dchftcs 4y ago
  I think a simpler way to put it is that the coordination of more body mass requires more analog input. It's not the case that a large muscle group in a body is sufficiently abstracted into something that only requires a small amount of input to do work. It makes intuitive sense to me that it requires more signal bandwidth to control more muscle cells at once, and in turn more computation to produce data that requires such bandwidth. A better analogy would then be saying that we need to treat cell groups of a certain mass roughly as one software application that has a certain level of computational resource requirements. The more such applications you have in your system, the more CPU and RAM you need to run them all. Another way to explain it is that an engine is a autonomous unit that has a specific function, and all you have to do is to instruct it, say, to run with higher or lower power. But most of the body has to be centrally controlled by the brain.
agumonkey 4y ago
Nature doesn't optimize like us. If the neuron count is function of tissue 'mass' then you'll have a larger brain. Just having larger skin surface (granted similar density of sensory cells) would be a reason to have more neuron to deal with more sensory inputs.
- Silverback_VII 4y ago
  >more neuron to deal with more sensory inputs. This makes some sense. However nature certainly does optimize as you can see with the sensory resolution from your hand vs the one from your back.
  - agumonkey 4y ago
    I know, I mentioned "like us", there are optimizations, just not necessarily the same as the one we'd put in place. ps: note that I'm not knowledgeable about the topic, I'm just picturing an easy coupling between more cells and more neurons. It might be a totally different reason, maybe whales have a different metabolysm / development causing more brain mass for unrelated reasons :)
amelius 4y ago
I think they don't need it. https://www.sciencealert.com/a-man-who-lives-without-90-of-his-brain-is-challenging-our-understanding-of-consciousness https://www.sciencealert.com/a-man-who-lives-without-90-of-h...
- layer8 4y ago
  > Rather than 90 percent of this man's brain being missing, it's more likely that it's simply been compressed into the thin layer you can see in the images above. I.e. whale brains could certainly be compressed more efficiently, but on the other hand, in a body the size of a whale, that probably doesn’t matter much.
im3w1l 4y ago
I think its correlation vs causation kind of. Brain-to-body size how important the brain is for the animal. A big animal can have a big brain, because why not. But for a small animal to have a big brain it means a certain sacrifice. This shows how much emphasis evolution has put on the brain. More emphasis leads to bigger brains, but more importantly to smarter wiring.
2-718-281-828 4y ago
Your statement already fails at the engine-brain analogy. Furthermore the brain controls muscle fibers. More and larger muscles means more muscle fibers to be connected to the brain. Also brain size and body mass simply correlate. [1] 1: https://en.wikipedia.org/wiki/Brain%E2%80%93body_mass_ratio#/media/File:Brain-body_mass_ratio_for_some_animals_diagram.svg https://en.wikipedia.org/wiki/Brain%E2%80%93body_mass_ratio#...

dbspin 4y ago

Because the engine analogy though intuitively appealing, doesn't accurately map onto the way organisms work. The 'nerves' which send control and sensory information to and from our organs are neurons. The 'extended brain' includes the central and peripheral nervous systems, and takes part in local and distributed cognition. So it's not a case of an engine running a machine, or a CPU controlling the information flowing from a bunch of subsystems. The neurocognitive architecture is spread across the body. Naturally more cerebral cortex is needed to perform higher order processing and control the signalling throughout the whales enormous nervous system.

dchftcs 4y ago
I think a simpler way to put it is that the coordination of more body mass requires more analog input. It's not the case that a large muscle group in a body is sufficiently abstracted into something that only requires a small amount of input to do work. It makes intuitive sense to me that it requires more signal bandwidth to control more muscle cells at once, and in turn more computation to produce data that requires such bandwidth. A better analogy would then be saying that we need to treat cell groups of a certain mass roughly as one software application that has a certain level of computational resource requirements. The more such applications you have in your system, the more CPU and RAM you need to run them all. Another way to explain it is that an engine is a autonomous unit that has a specific function, and all you have to do is to instruct it, say, to run with higher or lower power. But most of the body has to be centrally controlled by the brain.

agumonkey 4y ago

Nature doesn't optimize like us. If the neuron count is function of tissue 'mass' then you'll have a larger brain. Just having larger skin surface (granted similar density of sensory cells) would be a reason to have more neuron to deal with more sensory inputs.

Silverback_VII 4y ago
>more neuron to deal with more sensory inputs. This makes some sense. However nature certainly does optimize as you can see with the sensory resolution from your hand vs the one from your back.
- agumonkey 4y ago
  I know, I mentioned "like us", there are optimizations, just not necessarily the same as the one we'd put in place. ps: note that I'm not knowledgeable about the topic, I'm just picturing an easy coupling between more cells and more neurons. It might be a totally different reason, maybe whales have a different metabolysm / development causing more brain mass for unrelated reasons :)

amelius 4y ago

I think they don't need it. https://www.sciencealert.com/a-man-who-lives-without-90-of-his-brain-is-challenging-our-understanding-of-consciousness https://www.sciencealert.com/a-man-who-lives-without-90-of-h...

layer8 4y ago
> Rather than 90 percent of this man's brain being missing, it's more likely that it's simply been compressed into the thin layer you can see in the images above. I.e. whale brains could certainly be compressed more efficiently, but on the other hand, in a body the size of a whale, that probably doesn’t matter much.

im3w1l 4y ago

I think its correlation vs causation kind of. Brain-to-body size how important the brain is for the animal. A big animal can have a big brain, because why not. But for a small animal to have a big brain it means a certain sacrifice. This shows how much emphasis evolution has put on the brain. More emphasis leads to bigger brains, but more importantly to smarter wiring.

2-718-281-828 4y ago

Your statement already fails at the engine-brain analogy. Furthermore the brain controls muscle fibers. More and larger muscles means more muscle fibers to be connected to the brain. Also brain size and body mass simply correlate. [1] 1: https://en.wikipedia.org/wiki/Brain%E2%80%93body_mass_ratio#/media/File:Brain-body_mass_ratio_for_some_animals_diagram.svg https://en.wikipedia.org/wiki/Brain%E2%80%93body_mass_ratio#...