Thanks Robin! I have read this paper now, but it still doesn’t seem to address the arguments that orthonormal linked to :-/
The 1986 study appeared to me to be basically well done, offering a fascinating paradigm that could be extended in many directions for further research with a reasonably strong result by itself. It basically confirmed the positive claims of Marken that hierarchical arrangements of negative feedback loop systems (designed, with a handful of optimized parameters, and then left alone) can roughly reproduce trained human behavior in a variety of dynamically changing toy domains, supporting the contention that whatever is operating in the human nervous system after a period of training is doing roughly the same effective computations as the model.
In the text, Merken addresses the “motor control literature” as making claims whose refutation was partly the purpose of his experiments.
It required a little more googling to figure out the claims he was trying to reject… but basically he seems to be objecting to the claim that mammals work as open loop controllers (that is, generating action signals based on an internal model of the world that are sent into the world with no verification loop or secondary corrections). This claim appears to have been founded mostly on things called “deafferentiation experiments”… which turned out to be aesthetically horrifying and also turned out to not actually prove the general case of “open loop” claims.
a psychologist, who had cut afferent ganglia that supplied sensation to the brain from their arms and legs, then used restraint, electric shock, and withholding of food to force [the monkeys] to use the limbs they could not feel.
The ability of monkeys mutilated in this fashion to (eventually?) move around purposively was taken as evidence that there was not a hierarchically arranged set of negative feedback motor control systems implemented in their nervous system. In practice (after the scientist was arrested for animal cruelty, PETA’s request for custody was denied, and the monkeys were brainscanned, euthanized, and autopsied) it turned out that the monkey’s brains had been massively re-wired by the experience. The practical upshot of the experiments seem to have primarily been to serve as dramatic evidence of adult primate brain plasticity (which they didn’t believe in, back then?) rather than as confirmation of a negative feedback theory of motor control. (Probably there’s more to it than that, but this is my first draft understanding.)
Merken dismisses these experiments in part by pointing out the difficulty of preventing negative feedback control processes if there are many sub controllers that can use measurements partially correlated to the measure being optimized and concludes with falsification examples and criteria for the general theory and the particular model that are not subject to this objection:
Control theory does not rule out the possibility that some of the behavior produced by organisms is open loop. If a behavior is open loop then the effects of disturbances will not be resisted by system outputs. There is evidence, for example, that the saccadic eye positioning system is open loop. However, open-loop behavior is likely to be exceptionally rare …The two-level model could be tested by other means. One suggestion is to look for differences in the time to react to disturbances applied to controlled variables that are presumed to be at different levels—the higher the level of the variable, the slower the response to the effect of a disturbance. Another approach would be to trace out the required connections anatomically. The present study shows only that the two-level model is sufficient, not that it is necessary.
In short, I’m still impressed by Merken. His reasoning seems clean, his experiment, robust, his criticisms of motor-control and trait-theory, well reasoned. My very broad impression is that there may be a over-arching background argument here between “accurate model in the head producing aim and fire success” versus “incremental goal accomplishment via well tuned reflexes and continuous effort”? If that back story is operative then I guess my posterior probability was just pushed a little more in the direction of “reflexes and effort” over “models and plans”.
If there is some trick still lurking here, Orthonormal, that you could point me to and spell out in detail rather than by reference to assertions and hand-waving rationality heuristics, that would be appreciated. The more time I spend on Merken’s work, the more I find to appreciate. At this point, I’ve spend a day or two on this and I think the burden of proof is on you. If you take it up successfully I would be in your debt for rubbing a bit of sand out of my eyes :-)
Through judicious abuse of my employer’s resources, I have acquired a copy of the PDF—PM me an email address and I’ll send it to you.
Thanks Robin! I have read this paper now, but it still doesn’t seem to address the arguments that orthonormal linked to :-/
The 1986 study appeared to me to be basically well done, offering a fascinating paradigm that could be extended in many directions for further research with a reasonably strong result by itself. It basically confirmed the positive claims of Marken that hierarchical arrangements of negative feedback loop systems (designed, with a handful of optimized parameters, and then left alone) can roughly reproduce trained human behavior in a variety of dynamically changing toy domains, supporting the contention that whatever is operating in the human nervous system after a period of training is doing roughly the same effective computations as the model.
In the text, Merken addresses the “motor control literature” as making claims whose refutation was partly the purpose of his experiments.
It required a little more googling to figure out the claims he was trying to reject… but basically he seems to be objecting to the claim that mammals work as open loop controllers (that is, generating action signals based on an internal model of the world that are sent into the world with no verification loop or secondary corrections). This claim appears to have been founded mostly on things called “deafferentiation experiments”… which turned out to be aesthetically horrifying and also turned out to not actually prove the general case of “open loop” claims.
The most infamous of these experiments, (warning—kind of disturbing pictures) was basically:
The ability of monkeys mutilated in this fashion to (eventually?) move around purposively was taken as evidence that there was not a hierarchically arranged set of negative feedback motor control systems implemented in their nervous system. In practice (after the scientist was arrested for animal cruelty, PETA’s request for custody was denied, and the monkeys were brainscanned, euthanized, and autopsied) it turned out that the monkey’s brains had been massively re-wired by the experience. The practical upshot of the experiments seem to have primarily been to serve as dramatic evidence of adult primate brain plasticity (which they didn’t believe in, back then?) rather than as confirmation of a negative feedback theory of motor control. (Probably there’s more to it than that, but this is my first draft understanding.)
Merken dismisses these experiments in part by pointing out the difficulty of preventing negative feedback control processes if there are many sub controllers that can use measurements partially correlated to the measure being optimized and concludes with falsification examples and criteria for the general theory and the particular model that are not subject to this objection:
In short, I’m still impressed by Merken. His reasoning seems clean, his experiment, robust, his criticisms of motor-control and trait-theory, well reasoned. My very broad impression is that there may be a over-arching background argument here between “accurate model in the head producing aim and fire success” versus “incremental goal accomplishment via well tuned reflexes and continuous effort”? If that back story is operative then I guess my posterior probability was just pushed a little more in the direction of “reflexes and effort” over “models and plans”.
If there is some trick still lurking here, Orthonormal, that you could point me to and spell out in detail rather than by reference to assertions and hand-waving rationality heuristics, that would be appreciated. The more time I spend on Merken’s work, the more I find to appreciate. At this point, I’ve spend a day or two on this and I think the burden of proof is on you. If you take it up successfully I would be in your debt for rubbing a bit of sand out of my eyes :-)
Jennifer, here is where orthonormal seems to say where exactly Marken overfit the data.
(Orthonormal might not have seen your comment because you didn’t post it in reply to one of his/hers.)
[ETA: Nevermind. Looks like the date of orthonormal’s last comment is after yours, so he/she probably saw it.]