Do you have a sense of whether the case is any stronger for specifically using cortical and pallial neurons? That’s the approach Romain Espinosa takes in this paper, which is among the best work in economics on animal welfare.
I’m curious about this as well. I’m also really confused about the extent to which this measure is just highly correlated with overall neuron count. The wikipedia page on neuron and pallial/cortical counts in animals lists humans as having lower pallial/cortical neuron counts than orcas and elephants while “Animals and Social Welfare” lists the reverse. Based on the Wikipedia page, it seems that there is a strong correlation (and while I know basically nothing about neuroscience, I would maybe think the same arguments apply?). I looked at some of the papers that the wikipedia page cited and couldn’t consistently locate the cited number but they might have just had to multiply e.g. pallial neuron density by brain mass and I wouldn’t know which numbers to multiply.
I calculated ratios of neurons in the pallium (and mushroom bodies/corpora pedunculata in insects) vs whole brain/body from the estimates on that Wikipedia page not too long ago. In mammals, it was mostly 10-30%, with humans at 21.5%, and a few monkeys around 40%. Birds had mostly 20-70%, with red junglefowl (wild chickens) around 27.6%. The few insects where I got these ratios were:
Cockroach: 20%
Honey bee: 17.7%
Fruit fly: 2.5% (a low-valued outlier, but also the smallest brained animal for which I could get a ratio based on that table).
EDIT: Some of the insect mushroom body numbers might only be counting one hemisphere’s mushroom body neurons, and only intrinsic neurons, so the ratios might be too low. This might explain the low ratio for fruit flies.
There could also be some other issues that may make some of these comparisons unfair.
Oh interesting, thanks. Based on this it sounds super correlated (especially given that there are orders of magnitude difference between species in neuron counts).
It’s an interesting thought, although I’d note that quite a few prominent authors would disagree that the cortex is ultimately what matters for valence even in mammals (Jaak Panksepp being a prominent example). I think it’d also raise interesting questions about how to generalize this idea to organisms that don’t have cortices. Michael used mushroom bodies in insects as an example, but is there reason to think that mushroom bodies in insects are “like the cortex and pallium” but unlike various subcortical structures in the brain that also play a role in integrating information from different sensory sources? I think there’s need to be more of a specification of which types of neurons are ultimately counted in a principled way.
Do you have a sense of whether the case is any stronger for specifically using cortical and pallial neurons? That’s the approach Romain Espinosa takes in this paper, which is among the best work in economics on animal welfare.
I’m curious about this as well. I’m also really confused about the extent to which this measure is just highly correlated with overall neuron count. The wikipedia page on neuron and pallial/cortical counts in animals lists humans as having lower pallial/cortical neuron counts than orcas and elephants while “Animals and Social Welfare” lists the reverse. Based on the Wikipedia page, it seems that there is a strong correlation (and while I know basically nothing about neuroscience, I would maybe think the same arguments apply?). I looked at some of the papers that the wikipedia page cited and couldn’t consistently locate the cited number but they might have just had to multiply e.g. pallial neuron density by brain mass and I wouldn’t know which numbers to multiply.
I calculated ratios of neurons in the pallium (and mushroom bodies/corpora pedunculata in insects) vs whole brain/body from the estimates on that Wikipedia page not too long ago. In mammals, it was mostly 10-30%, with humans at 21.5%, and a few monkeys around 40%. Birds had mostly 20-70%, with red junglefowl (wild chickens) around 27.6%. The few insects where I got these ratios were:
Cockroach: 20%
Honey bee: 17.7%
Fruit fly: 2.5% (a low-valued outlier, but also the smallest brained animal for which I could get a ratio based on that table).
EDIT: Some of the insect mushroom body numbers might only be counting one hemisphere’s mushroom body neurons, and only intrinsic neurons, so the ratios might be too low. This might explain the low ratio for fruit flies.
There could also be some other issues that may make some of these comparisons unfair.
Oh interesting, thanks. Based on this it sounds super correlated (especially given that there are orders of magnitude difference between species in neuron counts).
It’s an interesting thought, although I’d note that quite a few prominent authors would disagree that the cortex is ultimately what matters for valence even in mammals (Jaak Panksepp being a prominent example). I think it’d also raise interesting questions about how to generalize this idea to organisms that don’t have cortices. Michael used mushroom bodies in insects as an example, but is there reason to think that mushroom bodies in insects are “like the cortex and pallium” but unlike various subcortical structures in the brain that also play a role in integrating information from different sensory sources? I think there’s need to be more of a specification of which types of neurons are ultimately counted in a principled way.