[NST==>So, I take it that from this last sentence, in red, you would define hunger as a pattern of activity in the brain that is predictive of feeding behavior, right. But not all feeding behavior, right? Only feeding behavior that is preceded by deprivation? What if you got feeding behavior that was not preceded by deprivation. What if you got deprivation, and the rat never ate: --it just wandered around the food filled cage looking restless and unhappy. What if all your variables didn't cluster as the concept "hunger" seems to demand?
If one has a set of related questions and convincing answers, then one can talk about weaving them together into a concept. If a question is "Why does this type of animal feed?", there could be preceding observables that are predictive of that, especially physiological observables. Likewise for "Why does this particular of animal fail to feed and others of its type do when deprived of food?" If there are a lot of animals of the type that fail to feed, when a model that predicts they should, that would not be a very good model, and the second question would have to be investigated and incorporated into the model. The animal is a physical system, a sort of machine, so and it can be taken apart and studied in parts. A concept cannot be a cause separate from the machine or the environment of the machine, and so it serves no purpose but to constrain the kind of spatial or temporal patterns to anticipate. It attacks its nematocyst prey when it needs them, stops when it has "enough." But the nematocysts play no role in the metabolism of the hydra. It captures other pray to feed in the ordinary sense. Is this a hunger? In many animals, the elements of prey orientation, search, chase, attack, immobilization, opening the prey, consumption and or storage, etc., don't line up in the way that the vernacular concept of hunger demands. It is a process to be understood on its own. As an analogy, a robot control system designed by conventional software engineering techniques might have subroutines for identifying targets, chasing them, immobilizing them, and so on. These subroutines could be adopted for the purpose of securing energy resources, or for some other purpose. If it is for securing energy, then one should look for logic conditionals in the control system that check the battery voltage (say). Likewise in a biological system, there better be signaling techniques in the organism that plausibly arise from lower-level metabolic indicators. To return to humans, and self-perception, for a moment, one of the family of variables that would seem to need to cluster with deprivation, and food getting activity is what we behaviorists call "self-report" : in this case, the answer to the question, "Are you hungry?" But like many self-report variables, hunger self-report measures do not necessarily cluster all that well with other presumptively measures of "hunger", whatever we might decide it to be. So, it becomes a real empirical question to ask what, in God's name, the subject is speaking to when he answers the question, "Are you hungry?". It seems to me to understand self-reports (higher brain function) one should get a reference point as to whether brain stem level processing of energy balance signals is really underway. They could be reporting "I'm anxious and eating reduces my anxiety" or some other convoluted thing, or they could be misrepresenting their feelings just for fun, etc. Marcus
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