Great post Jason! I have a good background in insect conditioning and navigation from my PhD so I hope that I can provide a useful contribution here.
I would have previously placed a higher weighting on classical conditioning as an indicator for valenced experience, but I wasn’t aware of the spinal cord conditioning studies on rodents. The spinal cord is classed as part of the central nervous system so we shouldn’t really surprised that it has some capacity for learning. Brains evolved simpler nervous structures which would also have benefited from some learning capability (so I’d expect some learning capacity in jellyfish nerve nets although I’m not sure they’ve been tested) so it makes sense that peripheral nervous circuits have maintained some capacity for learning, and this is probably evolutionary advantageous as it doesn’t put extra cognitive load on the brain.
A headless insect might even have quite a high relative learning capacity compared to a headless rodent (relative in the sense of what can be learnt by the body compared to the intact animal) - the ventral nerve cord (VNC) is quite complex, large relative to the brain (I don’t know the neuron ratio between VNC/spinal cord and brain for either vertebrates or insects, could be interesting to find this out), and contains the central pattern generator that coordinates locomotion. I’ve dissected quite a few insect heads and seen a lot of the bodies get up and walk away while headless. Diptera (flies) can fly while headless as the halteres provide gyroscopic feedback that stabilizes their attitude—once one of my headless hoverflies surprised my colleague when it flew into her hair while she was dissecting moth brains on the other side of the laboratory (true story). So it might be worth checking for studies in insect locomotory conditioning looking at the role of the VNC to see what is possible.
Aside, it’s fairly well known that if you do a bad job of cutting the head of a chicken and leave its brain stem intact then it can live quite a long life if it’s fed carefully. Would headless chickens fed through straws in a matrix-like factory farm suffer? That fact this feels repulsive while also seeming ethically preferable to factory farming intact chickens means something is wrong with this line of reasoning, right?
Anyway, back to conditioning. Allen et al. 2009 states:
spinal neurons belonging to the nociceptive system are sensitive to both Pavlovian and instrumental relations, and they exhibit a number of phenomena that when studied in normal, intact organisms, including human beings, are frequently described in cognitive or attentional terms. These phenomena include a distractor effect, latent inhibition and overshadowing, and learned helplessness effects. ... We have indicated ways we think spinal mechanisms are much more restricted in their capacities than brain mechanisms.
I didn’t read the paper in sufficient detail to determine which conditioning phenomena were not present in spinal cords but were possible with intact brains, but I would suggest that those would be better indicators of complex learning that implies valenced experience (likewise, pick the conditioning phenomena that don’t occur for sleeping people sleep). For instance, the discrimination can be made between elemental learning (where a stimulus is always reinforced, e.g. A+ B-) and non-elemental learning (where stimuli are not always reinforced, e.g. A+, B+, AB-); the latter is usually taken to imply higher cognitive demands and I would assume that non-elemental learning paradigms cannot be learnt without the intact brain. There are still more complicated associative conditioning tasks like transfer and rule learning that I think would also provide quite a strong indication of complex thought. Honeybees are indeed able to learn all of these in visual and olfactory conditioning tasks (Martin Giurfa has a great review on this, the 2nd section also discusses elemental vs. non-elemental learning and I took the examples from there. Also, see Randolf Menzel (more olfactory) and Mandyam Srinivasan (more visual) for other honeybee learning and memory reviews). Most learning paradigms from honeybees have probably also been tested on Drosophila, but I’m less familiar with that literature.
Likewise with multimodal conditioning that is outside of the usual input-output relationship an organism’s experience suggests some cognitive flexibility. For instance, I think the conditioning studies with spinal cords worked on nociceptive reflex circuits that were already present but, I wouldn’t expect their spinal cord to learn to associate a smell with a motor action (asides from the fact the neurons from the nose to the spinal cord were cut, imagine you kept all the olfactory neural connections and removed the rest of the rodent brain). However, intact organisms are able to learn to associate say, mechanosensory or visual cues (as a conditioned stimulus) with a food reward (the unconditioned stimulus that induces proboscis extension or salivation), despite the fact that the CS isn’t closely linked to a gustatory reflex (whereas smell/taste interacts closely with gustatory circuits).
Ok, I went into a bit more detail on this than planned, but I will come back to operant conditioning and navigation! Edited a bit for clarity and grammar.
(Apologies for the delayed response; I’ve been traveling the last few days.)
Again, thanks so much for the thoughtful and thought-provoking comments! My background is in philosophy, where the science of these issues gets handled at a rather superficial level, so it’s a pleasure to be able to correspond with someone with such a deep knowledge of the field.
The distinction between operant conditioning and operant conditioning with an unfamiliar action is somewhat arbitrary. We were trying to capture the fact that some types of learning require more cognitive flexibility than others. Perhaps the distinction between elemental and non-elemental learning is a more important one. There are probably a number of other important distinctions that I’ve either glossed over or just missed completely. I think it would be interesting to see a taxonomy of learning abilities and an analysis of which learning abilities give the strongest evidence for valenced experience. I certainly agree with you that contextual learning provides stronger evidence of cognitive flexibility than many other types of learning.
I’m interested to hear more about why you think novelty-seeking behavior might be evidence for the capacity for valenced experience. I suppose the fact that novelty salience can override innate preference is further evidence of behavioral plasticity. Is that what you had in mind or were you thinking of something more specific?
Definitely interested to hear your thoughts about navigation.
Hi Jason, apologies for my delayed reply as well. I’m quite interested in Invertebrate Sentience project and am happy to share some of my knowledge on these topics. My background was originally in robotics and I’ve worked on invertebrate sensory neuroscience from a fairly reductionist viewpoint (and wouldn’t previously have been very concerned by questions on consciousness!). While my research was always quite concentrated on vision in flying insects, I felt that I gained quite a well-rounded perspective on invertebrate neuroscience in the labs I worked at and the conference I went to. I think this might be quite common amongst invertebrate neuroscientists—compared to vertebrate fields there are a smaller number of people working on a larger range of organisms so I think there tends to be more intermingling of ideas. Funnily enough, the thing that probably took me longest to adapt to was not treating insects as little input-output automatons but I suspect that if you were to do some insect research your background would lead you to over-anthropomorphise. There is often a fine line between things you can reliably expect insects to do reflexively vs. similar tasks that result in much more variation in what they will do.
Agreed the learning is a complicated issue. My perspective was mostly in trying to separate out things that seem complicated because of the motor component compared to the complexity of the contextual component (which I agree is probably a more important indicator of cognitive flexibility). A taxonomy of learning capability would be interesting (I would assume psychologists have done this for human children), but I wonder if it would necessarily match between taxa—it is possible that different types of phenomenal learning can be performed by a variety of neural architectures, so some organisms may find non-elemental learning easier than elemental learning if that is what they have been exposed to most during evolution.
With regards to novelty, I think it could actually be something quite useful for indicating valanced experience. I’m not an expert on this, but I understand that as well as positively and negatively cued stimulus, novelty can act as a ‘bottom-up’ modulator for selective attention in flies. Further, mutant Drosophila that with abnormal response to novelty are found to have disturbances in learning and memory. Bruno van Swinderen’s lab is doing some interesting work on this, and he has discussed using ‘bottom-up’ modulators to investigate ‘top-down’ selective attention (which seems pretty key to subjective experience in humans). It is possible that novelty is analogous to positive reinforcement in some situations (like developmental learning) but I think Bruno would argue that it can be deeper, because it indicates the animal is actively engaged in learning new information about the world (and I’m sure he’d be happy to talk further on this if you’d like).
I hope to get to replying about navigation tomorrow :)
Great post Jason! I have a good background in insect conditioning and navigation from my PhD so I hope that I can provide a useful contribution here.
I would have previously placed a higher weighting on classical conditioning as an indicator for valenced experience, but I wasn’t aware of the spinal cord conditioning studies on rodents. The spinal cord is classed as part of the central nervous system so we shouldn’t really surprised that it has some capacity for learning. Brains evolved simpler nervous structures which would also have benefited from some learning capability (so I’d expect some learning capacity in jellyfish nerve nets although I’m not sure they’ve been tested) so it makes sense that peripheral nervous circuits have maintained some capacity for learning, and this is probably evolutionary advantageous as it doesn’t put extra cognitive load on the brain.
A headless insect might even have quite a high relative learning capacity compared to a headless rodent (relative in the sense of what can be learnt by the body compared to the intact animal) - the ventral nerve cord (VNC) is quite complex, large relative to the brain (I don’t know the neuron ratio between VNC/spinal cord and brain for either vertebrates or insects, could be interesting to find this out), and contains the central pattern generator that coordinates locomotion. I’ve dissected quite a few insect heads and seen a lot of the bodies get up and walk away while headless. Diptera (flies) can fly while headless as the halteres provide gyroscopic feedback that stabilizes their attitude—once one of my headless hoverflies surprised my colleague when it flew into her hair while she was dissecting moth brains on the other side of the laboratory (true story). So it might be worth checking for studies in insect locomotory conditioning looking at the role of the VNC to see what is possible.
Aside, it’s fairly well known that if you do a bad job of cutting the head of a chicken and leave its brain stem intact then it can live quite a long life if it’s fed carefully. Would headless chickens fed through straws in a matrix-like factory farm suffer? That fact this feels repulsive while also seeming ethically preferable to factory farming intact chickens means something is wrong with this line of reasoning, right?
Anyway, back to conditioning. Allen et al. 2009 states:
I didn’t read the paper in sufficient detail to determine which conditioning phenomena were not present in spinal cords but were possible with intact brains, but I would suggest that those would be better indicators of complex learning that implies valenced experience (likewise, pick the conditioning phenomena that don’t occur for sleeping people sleep). For instance, the discrimination can be made between elemental learning (where a stimulus is always reinforced, e.g. A+ B-) and non-elemental learning (where stimuli are not always reinforced, e.g. A+, B+, AB-); the latter is usually taken to imply higher cognitive demands and I would assume that non-elemental learning paradigms cannot be learnt without the intact brain. There are still more complicated associative conditioning tasks like transfer and rule learning that I think would also provide quite a strong indication of complex thought. Honeybees are indeed able to learn all of these in visual and olfactory conditioning tasks (Martin Giurfa has a great review on this, the 2nd section also discusses elemental vs. non-elemental learning and I took the examples from there. Also, see Randolf Menzel (more olfactory) and Mandyam Srinivasan (more visual) for other honeybee learning and memory reviews). Most learning paradigms from honeybees have probably also been tested on Drosophila, but I’m less familiar with that literature.
Likewise with multimodal conditioning that is outside of the usual input-output relationship an organism’s experience suggests some cognitive flexibility. For instance, I think the conditioning studies with spinal cords worked on nociceptive reflex circuits that were already present but, I wouldn’t expect their spinal cord to learn to associate a smell with a motor action (asides from the fact the neurons from the nose to the spinal cord were cut, imagine you kept all the olfactory neural connections and removed the rest of the rodent brain). However, intact organisms are able to learn to associate say, mechanosensory or visual cues (as a conditioned stimulus) with a food reward (the unconditioned stimulus that induces proboscis extension or salivation), despite the fact that the CS isn’t closely linked to a gustatory reflex (whereas smell/taste interacts closely with gustatory circuits).
Ok, I went into a bit more detail on this than planned, but I will come back to operant conditioning and navigation!
Edited a bit for clarity and grammar.
Hi Gavin!
(Apologies for the delayed response; I’ve been traveling the last few days.)
Again, thanks so much for the thoughtful and thought-provoking comments! My background is in philosophy, where the science of these issues gets handled at a rather superficial level, so it’s a pleasure to be able to correspond with someone with such a deep knowledge of the field.
The distinction between operant conditioning and operant conditioning with an unfamiliar action is somewhat arbitrary. We were trying to capture the fact that some types of learning require more cognitive flexibility than others. Perhaps the distinction between elemental and non-elemental learning is a more important one. There are probably a number of other important distinctions that I’ve either glossed over or just missed completely. I think it would be interesting to see a taxonomy of learning abilities and an analysis of which learning abilities give the strongest evidence for valenced experience. I certainly agree with you that contextual learning provides stronger evidence of cognitive flexibility than many other types of learning.
I’m interested to hear more about why you think novelty-seeking behavior might be evidence for the capacity for valenced experience. I suppose the fact that novelty salience can override innate preference is further evidence of behavioral plasticity. Is that what you had in mind or were you thinking of something more specific?
Definitely interested to hear your thoughts about navigation.
Hi Jason, apologies for my delayed reply as well. I’m quite interested in Invertebrate Sentience project and am happy to share some of my knowledge on these topics. My background was originally in robotics and I’ve worked on invertebrate sensory neuroscience from a fairly reductionist viewpoint (and wouldn’t previously have been very concerned by questions on consciousness!). While my research was always quite concentrated on vision in flying insects, I felt that I gained quite a well-rounded perspective on invertebrate neuroscience in the labs I worked at and the conference I went to. I think this might be quite common amongst invertebrate neuroscientists—compared to vertebrate fields there are a smaller number of people working on a larger range of organisms so I think there tends to be more intermingling of ideas. Funnily enough, the thing that probably took me longest to adapt to was not treating insects as little input-output automatons but I suspect that if you were to do some insect research your background would lead you to over-anthropomorphise. There is often a fine line between things you can reliably expect insects to do reflexively vs. similar tasks that result in much more variation in what they will do.
Agreed the learning is a complicated issue. My perspective was mostly in trying to separate out things that seem complicated because of the motor component compared to the complexity of the contextual component (which I agree is probably a more important indicator of cognitive flexibility). A taxonomy of learning capability would be interesting (I would assume psychologists have done this for human children), but I wonder if it would necessarily match between taxa—it is possible that different types of phenomenal learning can be performed by a variety of neural architectures, so some organisms may find non-elemental learning easier than elemental learning if that is what they have been exposed to most during evolution.
With regards to novelty, I think it could actually be something quite useful for indicating valanced experience. I’m not an expert on this, but I understand that as well as positively and negatively cued stimulus, novelty can act as a ‘bottom-up’ modulator for selective attention in flies. Further, mutant Drosophila that with abnormal response to novelty are found to have disturbances in learning and memory. Bruno van Swinderen’s lab is doing some interesting work on this, and he has discussed using ‘bottom-up’ modulators to investigate ‘top-down’ selective attention (which seems pretty key to subjective experience in humans). It is possible that novelty is analogous to positive reinforcement in some situations (like developmental learning) but I think Bruno would argue that it can be deeper, because it indicates the animal is actively engaged in learning new information about the world (and I’m sure he’d be happy to talk further on this if you’d like).
I hope to get to replying about navigation tomorrow :)