what is D&M’s mistaken assumption when it comes to motivations?

Davis and Moore (D&M), “Some Principles of Stratification” (TIR Ch. 2);

-Tumin, “Some Principles of Stratification: A Critical Analysis”

Prompt: Please describe the overall argument of Davis and Moore’s original article “Some Principles of Stratification,” as well as Tumin’s criticism of Davis and Moore.
For a full grade of 10 points, please be sure to address all of the following questions in your response:
1.*D&M make a certain argument regarding the relative “rarity” of highly skilled/talented people. For D&M, why might this rarity entitle these skilled people to higher rewards? How does Tumin critique this theory? For Tumin, what might account for the ostensible “rarity” of talent?

* According to Tumin, what is D&M’s mistaken assumption when it comes to motivations? Does Tumin argue that D&M have a too-narrow conception of possible motivations, or too broad?
* D&M argue that high rewards are a necessary incentive for those who make great sacrifices (i.e., the time and cost of medical school). Tumin call this “the least critically thought-out” position in D&M’s article. Why is this so?