Hello Jason. Thanks for doing all this work! I haven’t kept up with all of it, so apologies if you’ve covered this elsewhere, but I had a nascent thought that links and challenges your two tentative conclusions.
Okay, so the idea is that valenced states—colloquially, pleasure and pain—provide “oomph” to get creatures to do things. That seems fine. But it’s unclear what this tells us about the intensities of experiences. Imagine we have two creatures that are the same, except A has 10x valence intensity than B. Why should there be any difference about how the two of them behave and thus, their evolutionary fitness? Couldn’t they just act in the same way? And supposing more oomph is better, how much oomph should we expect, given there are, e.g. energy costs to producing sensations?
From the armchair, what matters for behaviour the relative intensity of different things for a given creature: if the deer loves eating berries and doesn’t fear pain enough to run away from wolves, it will get eaten. But that doesn’t tell us about inter-creature cardinal intensities.
My thought is something like this. Creatures need a range of cardinal intensities large enough to allow them to choose between all the different behaviours they need to undertake to survive and reproduce. As a toy example, if you only have 3 levels of pleasure—zero, 1, and 2 - but you have very many different choices to make—eat, mate, run away, sleep, etc. - then that’s not enough resolution to make decisions. An entity that needs to make more decisions needs a greater range of sensations.
This takes us back, crude, to something about brain size a proxy for valenced states. And the possibility that ‘simple’ creatures, i.e. those that don’t have lots of decisions to make, don’t feel very much. I’m not sure where that leaves us in practice.
Thanks for your comment! The point you raise is a good one. I’ve thought about related issues over the last few months, but my views still aren’t fully settled. And I’ll just reiterate for readers that my tentative conclusions are just that: tentative. More than anything, I want everyone to appreciate how much uncertainty we face here.
We can crudely ask whether motivation is tied to the relative intensity of valenced experience or the absolute intensity of valenced experience. (‘Crudely’ because the actual connection between motivation and valenced experience is likely to be a bit messy and complicated.) If it’s the relative intensity, then, all else equal, a pain at the top end of an animal’s range is going to be very motivating, even if the pain has a phenomenal feel comparable to a human experiencing a very mild muscle spasm. If it’s absolute intensity, then, all else equal, a pain like that won’t be very motivating. I’m not sure what the right view is here, but the relative view that you endorse in the comment is certainly a live option, so let’s go with that.
If it’s relative intensity that matters for motivation, then natural selection needs a reason to generate big differences in absolute intensity. (Setting aside the fact that evolution sometimes goes kinda haywire.) You suggest the fitness benefit of a fine-grained valence scale, especially for animals that face many competing pulls on their attention. I agree that the resolution of an animal’s valence scale probably matters. But it’s unclear to me how much this tells us about differences in absolute intensity.
It seems possible to be better or worse at distinguishing gradations of valenced experience. It might be the case that animals with similar intensity ranges can differ in the number of intensity levels they can distinguish. (It might also be the case that animals with different intensity ranges have a similar number of intensity levels they can distinguish.) So if there were a fitness benefit to having 100 distinguishable gradations rather than 10, evolution could either select for animals with wider ranges or select for animals with better resolutions. (Or some combination thereof.) Considerations like the Weber-Fechner law incline me toward thinking an increase in resolution would be more efficient than an increase in range (though of course there are limits to how much resolution can be increased). But at this point I’m just speculating; there’s a lot more basic research that needs to be done to get a handle on these sorts of questions.
As far as I know, it’s plausible to me that different neuron firing rates can represent different degrees of valence pretty close to continuously, so extra neurons might not be necessary to increase the resolution.
There are practical limitations about the resolution with which neurons can increase resolution (noise would be limiting factor, maybe other considerations). A common ‘design scheme’ that gets around this is range fractionation: If the receptors are endowed with distinct transfer functions in such a way that the points of highest sensitivity are scattered along the axis of the quality being measured, the precision of the sense organ as a whole can be increased. This example of mechanosensory neural encoding in hawkmoths is a good example of range fractionation (and where I first heard about it).
Range fractionation is one common example where extra neurons increase resolution. There may be other ways that neural resolution can be increased without extra neurons. Also note that this has mostly been studied in peripheral sensory systems—I’m not sure if similar encoding schemes have been considered to represent the resolution of subjective experiences that are solely represented in the CNS.
Hello Jason. Thanks for doing all this work! I haven’t kept up with all of it, so apologies if you’ve covered this elsewhere, but I had a nascent thought that links and challenges your two tentative conclusions.
Okay, so the idea is that valenced states—colloquially, pleasure and pain—provide “oomph” to get creatures to do things. That seems fine. But it’s unclear what this tells us about the intensities of experiences. Imagine we have two creatures that are the same, except A has 10x valence intensity than B. Why should there be any difference about how the two of them behave and thus, their evolutionary fitness? Couldn’t they just act in the same way? And supposing more oomph is better, how much oomph should we expect, given there are, e.g. energy costs to producing sensations?
From the armchair, what matters for behaviour the relative intensity of different things for a given creature: if the deer loves eating berries and doesn’t fear pain enough to run away from wolves, it will get eaten. But that doesn’t tell us about inter-creature cardinal intensities.
My thought is something like this. Creatures need a range of cardinal intensities large enough to allow them to choose between all the different behaviours they need to undertake to survive and reproduce. As a toy example, if you only have 3 levels of pleasure—zero, 1, and 2 - but you have very many different choices to make—eat, mate, run away, sleep, etc. - then that’s not enough resolution to make decisions. An entity that needs to make more decisions needs a greater range of sensations.
This takes us back, crude, to something about brain size a proxy for valenced states. And the possibility that ‘simple’ creatures, i.e. those that don’t have lots of decisions to make, don’t feel very much. I’m not sure where that leaves us in practice.
Hey Michael,
Thanks for your comment! The point you raise is a good one. I’ve thought about related issues over the last few months, but my views still aren’t fully settled. And I’ll just reiterate for readers that my tentative conclusions are just that: tentative. More than anything, I want everyone to appreciate how much uncertainty we face here.
We can crudely ask whether motivation is tied to the relative intensity of valenced experience or the absolute intensity of valenced experience. (‘Crudely’ because the actual connection between motivation and valenced experience is likely to be a bit messy and complicated.) If it’s the relative intensity, then, all else equal, a pain at the top end of an animal’s range is going to be very motivating, even if the pain has a phenomenal feel comparable to a human experiencing a very mild muscle spasm. If it’s absolute intensity, then, all else equal, a pain like that won’t be very motivating. I’m not sure what the right view is here, but the relative view that you endorse in the comment is certainly a live option, so let’s go with that.
If it’s relative intensity that matters for motivation, then natural selection needs a reason to generate big differences in absolute intensity. (Setting aside the fact that evolution sometimes goes kinda haywire.) You suggest the fitness benefit of a fine-grained valence scale, especially for animals that face many competing pulls on their attention. I agree that the resolution of an animal’s valence scale probably matters. But it’s unclear to me how much this tells us about differences in absolute intensity.
It seems possible to be better or worse at distinguishing gradations of valenced experience. It might be the case that animals with similar intensity ranges can differ in the number of intensity levels they can distinguish. (It might also be the case that animals with different intensity ranges have a similar number of intensity levels they can distinguish.) So if there were a fitness benefit to having 100 distinguishable gradations rather than 10, evolution could either select for animals with wider ranges or select for animals with better resolutions. (Or some combination thereof.) Considerations like the Weber-Fechner law incline me toward thinking an increase in resolution would be more efficient than an increase in range (though of course there are limits to how much resolution can be increased). But at this point I’m just speculating; there’s a lot more basic research that needs to be done to get a handle on these sorts of questions.
As far as I know, it’s plausible to me that different neuron firing rates can represent different degrees of valence pretty close to continuously, so extra neurons might not be necessary to increase the resolution.
There are practical limitations about the resolution with which neurons can increase resolution (noise would be limiting factor, maybe other considerations). A common ‘design scheme’ that gets around this is range fractionation: If the receptors are endowed with distinct transfer functions in such a way that the points of highest sensitivity are scattered along the axis of the quality being measured, the precision of the sense organ as a whole can be increased.
This example of mechanosensory neural encoding in hawkmoths is a good example of range fractionation (and where I first heard about it).
Range fractionation is one common example where extra neurons increase resolution. There may be other ways that neural resolution can be increased without extra neurons. Also note that this has mostly been studied in peripheral sensory systems—I’m not sure if similar encoding schemes have been considered to represent the resolution of subjective experiences that are solely represented in the CNS.