In my perspective, Psychological Hedonism is problematic. In general, they claim that "to seek pleasure and avoid pain" is the ultimate motivation of any action. In the spirit of Reductio ad Absurdum, we may suppose that this claim is valid. Therefore, any human's action in the history can to be attributed to either seeking pleasure or avoiding pain. Certainly, scientific research, which is a practice believed to be both rationally and morally right should be able to be analyzed under this platform. First, we may consider, if scientific research is motivated by avoiding pain. Of course some research in Medical science is motivated by it, but many other research such as Newton's research in Mechanics and Astronomy or Darwin's research in natural history/Biology is not related to any physical or mental "pain". Then, according to our assumption, these kind of research should be motivated by seeking pleasure. However, if we carefully check the history, we will find that many people do research simply because they want to know something, but not because of the pleasure may associate to the success of a research project. Analogously, if we lives in a cave (as in Plato's famous story), and one day we find a way to the outer world. Since we don't know whether it will bring us fortune or disaster, the exploration to the outer world can only be motivated by the curiosity itself, but not the expectation of pleasure as we don't know what's in the outer world and cannot make any reasonable expectation. And scientific research is very similar to this case. Hence we've find a contradiction in our argument. According to Reductio ad Absurdum, our assumption, i.e., Psychological Hedonism is problematic.