Why are there differences in pain tolerances?

This paper deals with the many different reasons why a quarter the population are stotics, another quarter are weak, and the rest of the half are somewhere in between. It has the psychological reasons and the scientific reasons(like the val and met genes, and the mu-opioid). There are probably some grammatical mistakes, and I apoligize for this. Pain, according to Coach Eric Anderson of the University of California Irvine, is a subjective, psychological phemonenon. …

…for different pain tolerances have been studied, or even detected yet, but the preceding information gives a good argument of why some people are wimps and others, who have almost no physical differences, are total stotics. More research needs to be done, but I believe that the information that I have acquired is adequate enough to fulfill this assignment. * Zubieta's colleagues include Mary Heitzig, Yolanda Smith, Joshua Bueller, Yanjun Xu, Robert Koeppe, and Christian Stohler.