LW - (Appetitive, Consummatory) (RL, reflex) by Steven Byrnes

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Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: (Appetitive, Consummatory) (RL, reflex), published by Steven Byrnes on June 17, 2024 on LessWrong.
"Appetitive" and "Consummatory" are terms used in the animal behavior literature. I was was briefly confused when I first came across these terms (a year or two ago), because I'm most comfortable thinking in terms of brain algorithms, whereas these terms were about categories of behavior, and the papers I was reading didn't spell out how the one is related to the other.
I'm somewhat embarrassed to write this because the thesis seems so extremely obvious to me now, and it's probably obvious to many other people too. So if you read the title of this post and were thinking "yeah duh", then you already get it, and you can stop reading.
Definition of "appetitive" and "consummatory"
In animal behavior there's a distinction between "appetitive behaviors" and "consummatory behaviors". Here's a nice description from Hansen et al. 1991 (formatting added, references omitted):
It is sometimes helpful to break down complex behavioral sequences into appetitive and consummatory phases, although the distinction between them is not always absolute.
Appetitive behaviors involve approach to the appropriate goal object and prepare the animal for consummatory contact with it. They are usually described by consequence rather than by physical description, because the movements involved are complex and diverse.
Consummatory responses, on the other hand, depend on the outcome of the appetitive phase. They appear motorically rigid and stereotyped and are thus more amenable to physical description. In addition, consummatory responses are typically activated by a more circumscribed set of specific stimuli.
So for example, rat mothers have a pup retrieval behavior; if you pick up a pup and place it outside the nest, the mother will walk to it, pick it up in her mouth, and bring it back to the nest.
The walking-over-to-the-pup aspect of pup-retrieval is clearly appetitive. It's not rigid and stereotyped; for example, if you put up a trivial barrier between the rat mother and her pup, the mother will flexibly climb over or walk around the barrier to get to the pup.
Whereas the next stage (picking up the pup) might be consummatory (I'm not sure). For example, if the mother always picks up the pup in the same way, and if this behavior is innate, and if she won't flexibly adapt in cases where the normal method for pup-picking-up doesn't work, then all that would be a strong indication that pup-picking-up is indeed consummatory.
Other examples of consummatory behavior: aggressively bristling and squeaking at an unwelcome intruder, or chewing and swallowing food.
How do "appetitive" & "consummatory" relate to brain algorithms?
Anyway, here's the "obvious" point I want to make. (It's a bit oversimplified; caveats to follow.)
Appetitive behaviors are implemented via an animal's reinforcement learning (RL) system. In other words, the animal has experienced reward / positive reinforcement signals when a thing has happened in the past, so they take actions and make plans so as to make a similar thing happen again in the future. RL enables flexible, adaptable, and goal-oriented behaviors, like climbing over an obstacle in order to get to food.
Consummatory behaviors are generally implemented via the triggering of specific innate motor programs stored in the brainstem. For example, vomiting isn't a behavior where the end-result is self-motivating, and therefore you systematically figure out from experience how to vomit, in detail, i.e. which muscles you should contract in which order. That's absurd! Rather, we all know that vomiting is an innate motor program.
Ditto for goosebumps, swallowing, crying, laughing, various facial expressions, orienting to unexpected sounds, flinching, and many more.
There are many s...