Harvard students, outraged over a doctoral dissertation arguing that Hispanic immigrants lack “raw cognitive ability or intelligence,” this week urged the university to investigate how the thesis came to be approved and to ban future research on racial superiority. The students presented 1,200 signatures to president Drew Faust and the dean of the John F. Kennedy School of Government, David Ellwood. “Academic freedom and a reasoned debate are essential to our academic community,” the petition said. “However, the Harvard Kennedy School cannot ethically stand behind academic work advocating a national policy of exclusion and advancing an agenda of discrimination.” …