Indeed, we have evidence that withdrawal behavior is frequently unconscious. Noxious stimulation can cause humans in vegetative states to yell, withdraw or display ‘pained’ facial expressions (Laureys 2007).
While I think the point is correct that pain reflexes can occur unconsciously, I would be wary of using humans in a vegetative state as a clean example of unconsciousness. A significant minority of patients in a diagnosed vegetative state without behavioural responses are nevertheless able to follow auditory commands. The classic paradigm uses instructions to ‘imagine playing tennis’ or ‘imagine walking around your home’ and detect the resulting distinctive fMRI or EEG signatures—where some patients can use their choice of imagined activity to communicate and answer binary questions!
Thanks for this observation, Ben. I agree that this isn’t the cleanest example. Maybe the best examples are in animals—e.g., headless frogs whose legs still try to remove acid from their skin. But I’m sure Joe has his own thoughts about this.
Hi Ben—Thanks for this. I agree that the PVS case is tricky, and probably not the best example. I assume that you are claiming that PVS patients are still phenomenally conscious, and that you are pointing to this study. (Note though that the authors never use “phenomenally conscious”.) However, as expected, the Owen et al study is controversial. I find this paper helpful when it comes to understanding some of the underlying methodological issues. One issue is whether these patients actually have intentional agency—perhaps suggested by their task responses—as this is often used as the diagnostic criterion for inferring that these subjects are (minimally?) conscious. It’s unclear whether they have such agency (see here), although this would not itself eliminate consciousness. So, fair point!
I agree—it’s very unclear what the level of intention, awareness, or phenomenal consciousness is in these cases. The 2006 study is definitely the foundational one, but there’s a decent amount of subsequent literature (though without much further clarity). I thought of this point because I’m currently reading Anil Seth’s 2021 book on the neuroscience of consciousness, “Being You”, which covers the topic quite well. (I’d highly recommend it to other interested readers!) But this was a very minor nitpick on a fascinating report—well done!
While I think the point is correct that pain reflexes can occur unconsciously, I would be wary of using humans in a vegetative state as a clean example of unconsciousness. A significant minority of patients in a diagnosed vegetative state without behavioural responses are nevertheless able to follow auditory commands. The classic paradigm uses instructions to ‘imagine playing tennis’ or ‘imagine walking around your home’ and detect the resulting distinctive fMRI or EEG signatures—where some patients can use their choice of imagined activity to communicate and answer binary questions!
Thanks for this observation, Ben. I agree that this isn’t the cleanest example. Maybe the best examples are in animals—e.g., headless frogs whose legs still try to remove acid from their skin. But I’m sure Joe has his own thoughts about this.
Hi Ben—Thanks for this. I agree that the PVS case is tricky, and probably not the best example. I assume that you are claiming that PVS patients are still phenomenally conscious, and that you are pointing to this study. (Note though that the authors never use “phenomenally conscious”.) However, as expected, the Owen et al study is controversial. I find this paper helpful when it comes to understanding some of the underlying methodological issues. One issue is whether these patients actually have intentional agency—perhaps suggested by their task responses—as this is often used as the diagnostic criterion for inferring that these subjects are (minimally?) conscious. It’s unclear whether they have such agency (see here), although this would not itself eliminate consciousness. So, fair point!
I agree—it’s very unclear what the level of intention, awareness, or phenomenal consciousness is in these cases. The 2006 study is definitely the foundational one, but there’s a decent amount of subsequent literature (though without much further clarity). I thought of this point because I’m currently reading Anil Seth’s 2021 book on the neuroscience of consciousness, “Being You”, which covers the topic quite well. (I’d highly recommend it to other interested readers!)
But this was a very minor nitpick on a fascinating report—well done!