Is my brain a utility minimizer? Or, the mechanics of labeling things as “work” vs. “fun”

I recently encountered something that is, in my opinion, one of the most absurd failure modes of the human brain. I first encountered this after introspection on useful things that I enjoy doing, such as programming and writing. I noticed that my enjoyment of the activity doesn’t seem to help much when it comes to motivation for earning income. This was not boredom from too much programming, as it did not affect my interest in personal projects. What it seemed to be, was the brain categorizing activities into “work” and “fun” boxes. On one memorable occasion, after taking a break due to being exhausted with work, I entertained myself, by programming some more, this time on a hobby personal project (as a freelancer, I pick the projects I work on so this is not from being told what to do). Relaxing by doing the exact same thing that made me exhausted in the first place.

The absurdity of this becomes evident when you think about what distinguishes “work” and “fun” in this case, which is added value. Nothing changes about the activity except the addition of more utility, making a “work” strategy always dominate a “fun” strategy, assuming the activity is the same. If you are having fun doing something, handing you some money can’t make you worse off. Making an outcome better makes you avoid it. Meaning that the brain is adopting a strategy that has a (side?) effect of minimizing future utility, and it seems like it is utility and not just money here—as anyone who took a class in an area that personally interested them knows, other benefits like grades recreate this effect just as well. This is the reason I think this is among the most absurd biases—I can understand akrasia, wanting the happiness now and hyperbolically discounting what happens later, or biases that make something seem like the best option when it really isn’t. But knowingly punishing what brings happiness just because it also benefits you in the future? It’s like the discounting curve dips into the negative region. I would really like to learn where is the dividing line between which kinds of added value create this effect and which ones don’t (like money obviously does, and immediate enjoyment obviously doesn’t). Currently I’m led to believe that the difference is present utility vs. future utility, (as I mentioned above) or final vs. instrumental goals, and please correct me if I’m wrong here.

This is an effect that has been studied in psychology and called the overjustification effect, called that because the leading theory explains it in terms of the brain assuming the motivation comes from the instrumental gain instead of the direct enjoyment, and then reducing the motivation accordingly. This would suggest that the brain has trouble seeing a goal as being both instrumental and final, and for some reason the instrumental side always wins in a conflict. However, its explanation in terms of self-perception bothers me a little, since I find it hard to believe that a recent creation like self-perception can override something as ancient and low-level as enjoyment of final goals. I searched LessWrong for discussions of the overjustification effect, and the ones I found discussed it in the context of self-perception, not decision-making and motivation. It is the latter that I wanted to ask for your thoughts on.