I recently encountered a blog entry by the eminent (and often wrong) economist Greg Mankiw . In his blog he notes that the ex-president of Harvard, the economist Larry Summers, asked a dean at Harvard if it isn't true that "in general, economists are smarter than political scientists, and political scientists are smarter than sociologists?" Mankiw then links to these 2002 data of GRE scores by field of Ph.D. study (with the obligatory "joke" that public administration is at the bottom of the hierarchy):
There are two big problems with Mankiw's claim that Larry Summers is "vindicated." First, does the GRE measure what it means to be "smart"? As much as I'd like to think so (since I scored in the 99th percentile on the GRE), the answer is a resounding no. The GRE is not recognized by Mensa, the high IQ society, as a legitimate IQ test. The lack of validity of the GRE as an IQ test is echoed by Educational Testing Service (ETS), the company that created the GRE, which has since removed the analytical section of the GRE listed above and replaced it with a writing section. And of course we should not forget that the GRE does not even attempt to measure the multitude of intelligences discussed by Robert J. Sternberg and Howard Gardner: social, emotional, visual, and so forth. Intelligence has likely evolved into a system of modules in the brain embodying different capabilities rather than a single, unitary construct that can be organized on one dimension (or a small number of dimensions).
Second, even if the GRE does measure what it means to be "smart," is there any reason to think these differences will persist after entry into graduate school? Again, there are serious problems with such a claim. Sociologists (especially vis-a-vis economists) are an especially diverse group of people: we are more likely to be female, non-white, and come from poorer backgrounds. These disadvantages can lead to stereotype threat (as discussed by the late John Ogbu) or other forms of test anxiety, resulting in lower test scores even when such tests measure raw intelligence. Moreover, the GRE scores listed above are only those for Doctoral students who enter programs, not those who exit them; given the difficulty of academic work, it is likely the differences between fields become flattened when you compare students who graduate with degrees. Finally, the GRE scores above ignore possible cohort effects: it is possible current sociology faculty score just as highly as current faculty in economics.
In short, pace Mankiw, Summers has not been "vindicated."