I interpret the brain size data differently. That a cow is not smarter than a mouse shows that most of brain size is used up controlling a larger body. That a whale has a large brain shows that large brains work. Animals with slightly larger brains than predicted by body size are smarter (apes, dolphins, ravens). This can probably be pushed further.
(I don’t understand why a large body should require extra neurons. One explanation is that resolution of touch is independent of size. Is this true? Why would a large animal need fine resolution? This would only explain a 2⁄3 exponent, not the observed 3⁄4. Neurons for controlling muscle probably scale at a full rate, but they needn’t clog up the brain.)
So let me rephrase my question in terms of output: do large animals have the same resolution of muscular control as small animals? Or do they have coarser control? If I’m 100x as tall as a mouse, do I have 100x as much control over the angle of my elbow? What good would that be? Can I pick up as small objects as a mouse? Why would I want to?
ETA: and even if I could, I think that would only explain a scaling exponent of 1⁄3, not the observed 3⁄4.
Of course you can pick up objects as small as a mouse. How do you operate your computer otherwise? :D
I often find it useful to finely control how much force I apply, e.g. threading a needle or walking barefoot on rocks. I don’t know that my control over how much force I apply has to be as fine as a mouse’s, but pretty near.
Along those lines, I think the bigger brain is needed to move bigger limbs around, more electric power to signal the muscles but I haven’t been able to find a citation.
I think that’s what Douglas_Knight was getting at with the “controlling muscle… needn’t clog up the brain” comment. If the trouble is that muscles need a amplified electrical signal, why not send data from a small efficient brain down small efficient nerves then amplify those signals right next to the muscle?
There’s probably some design constraint we don’t see, though. Whales have much bigger brains than humans, but those brains seem to be composed of fewer neurons and far far more glial cells...
I interpret the brain size data differently. That a cow is not smarter than a mouse shows that most of brain size is used up controlling a larger body. That a whale has a large brain shows that large brains work. Animals with slightly larger brains than predicted by body size are smarter (apes, dolphins, ravens). This can probably be pushed further.
(I don’t understand why a large body should require extra neurons. One explanation is that resolution of touch is independent of size. Is this true? Why would a large animal need fine resolution? This would only explain a 2⁄3 exponent, not the observed 3⁄4. Neurons for controlling muscle probably scale at a full rate, but they needn’t clog up the brain.)
It looks like having more brainpower controlling muscles is all sorts of useful, for example determining how finely you can do fine motor control.
So let me rephrase my question in terms of output: do large animals have the same resolution of muscular control as small animals? Or do they have coarser control? If I’m 100x as tall as a mouse, do I have 100x as much control over the angle of my elbow? What good would that be? Can I pick up as small objects as a mouse? Why would I want to?
ETA: and even if I could, I think that would only explain a scaling exponent of 1⁄3, not the observed 3⁄4.
Of course you can pick up objects as small as a mouse. How do you operate your computer otherwise? :D
I often find it useful to finely control how much force I apply, e.g. threading a needle or walking barefoot on rocks. I don’t know that my control over how much force I apply has to be as fine as a mouse’s, but pretty near.
Along those lines, I think the bigger brain is needed to move bigger limbs around, more electric power to signal the muscles but I haven’t been able to find a citation.
I think that’s what Douglas_Knight was getting at with the “controlling muscle… needn’t clog up the brain” comment. If the trouble is that muscles need a amplified electrical signal, why not send data from a small efficient brain down small efficient nerves then amplify those signals right next to the muscle?
There’s probably some design constraint we don’t see, though. Whales have much bigger brains than humans, but those brains seem to be composed of fewer neurons and far far more glial cells...