The irony is that a lot of statistics has really been developed in psychology and allied disciplines without even realizing. Meta-analysis, for example, really developed into its modern form in psychology, as a way of examining psychotherapy effects (even though the basic idea was around beforehand). Deep learning models too also have their roots in psychological models. They're called neural networks, but the models are more psychological than neurobiological per se, and have connections to other models that are firmly in the realm of psychological models.
By your reasoning no sciences should exist until we completely understand the mechanisms at a lower level.
Plenty of phenomena are observed and even experimentally manipulated all the time without understanding mechanisms. This happens in lots of biology all the time--infectious disease being one prominent example but there are thousands of other examples you could pick. This also happens with various phenomena in physics and chemistry as well, and is routine in astronomy (minus the experiments perhaps).
The undergrad student example is an armchair criticism, but think about it carefully: if the process you're studying shouldn't vary across populations, in a fundamental way, why does it matter if you use undergrads or 40 year old engineers?
Ego depletion is not such an unreasonable hypothesis. People perceive many things as effortful, and become exhausted. Try running a marathon for example, and tell me there's no such thing as fatigue.
A similar thing is also reported and observed for temptation. This is extremely common, so much so that people here are variously posting that the presence of the effect is obvious, and its absence is obvious. It's a bedrock idea invoked by all sorts of people all the time in explaining unhealthy behavior. It's also not unreasonable to assume, for example, that glucose in the brain is a limited resource, and that certain pathways are involved in certain types of tasks more, and might need rest. But you don't need to study the brain to examine whether depletion exists as a phenotype.
The effect in question is about the depletion idea, period, not about the mechanism. And you don't need a mechanism to study whether or not it exists.
Your final sentence betrays the problem in your reasoning: various lines of reasoning, including this paper but not limited to it, and involving all sorts of behavioral tasks, suggest that the depletion effect does not exist. So what insight is there to have in a mechanism that is not present? It's an illusion. This seems nontrivial to me.
Uncivil attacks will get you banned here. Please don't do that.
Also, would you please stop bulk-creating HN accounts? This is in the site guidelines: https://news.ycombinator.com/newsguidelines.html. HN is a community. If users don't have some consistent identity for others to relate to, we may as well have no usernames and no community at all. That would be quite a different kind of forum. Anonymity is fine, and throwaways for a specific purpose are ok—just not routinely.
