Okay, we agree that the simple robot described here is behaviorist and the thermostat is PCT. And I certainly see where you're coming from with the rats being PCT because hunger only works as a motivator if you're hungry. But I do have a few questions:

1. There are some things behaviorism can explain pretty well that I don't know how to model in PCT. For example, consider heroin addiction. An animal can go its whole life not wanting heroin until it's exposed to some. Then suddenly heroin becomes extraordinarily motivating and it will preferentially choose shots of heroin to food, water, or almost anything else. What is the PCT explanation of that?

2. I'm not entirely sure which correlation studies you're talking about here; most psych studies I read are done in an RCT type design and so use p-values rather than r-values; they can easily end up with p < .001 if they get a large sample and a good hypothesis. Some social psych studies work off of correlations (eg correlation between being observer-rated attractiveness and observer-rated competence at a skill); correlations are "lamentably low" in social psychology because high level processes (like opinion formation, social interaction, etc.) have a lot of noise. Are there any PCT studies of these sorts of processes (not simple motor coordination problems) that have any higher correlation than standard models do? Any with even the same level of correlation?

3. What's the difference between control theory and stimulus-response in a context? For example, if we use a simplified version of hunger in which the hormone leptin is produced in response to hunger and the hormone ghrelin is produced in response to satiety, we can explain this in two ways: the body is trying to PCT itself to the perfect balance of leptin and ghrelin, or in the context of the stimulus leptin the response of eating is rewarded and in the context of the stimulus ghrelin the response of eating is punished. Are these the same theory, or are there experiments that would distinguish between them? Do you know of any?

4. Does PCT still need reinforcement learning to explain why animals use some strategies and not others to achieve equilibrium? For example, when a rat in a Skinner box is hungry (ie its satiety variable has deviated in the direction of hunger), and then it presses a lever and gets a food pellet and its satiety variable goes back to its reference range, would PCTists explain that as getting rewarded for pressing the lever and expect it to press the lever again next time it's hungry?