David Michael Jacobs’s day-job is to be an American Historian and, well, recently retired Associate Professor of History at Temple University specializing in twentieth century American history and culture. When he is not a historian, however, Jacobs does Ufology, and he has a high profile in that field for his “research” and books about alien abductions, as well as for his lectures, interviews, and participation in TV shows.
Over his career, and due to failure to correct for rampant confirmation bias, Jacobs has gradually deteriorated into sheer crankery, and in recent years he has argued publicly that the evidence from his research, which sometimes includes utilizing hypnotic regression with alleged alien abductees along with traditional interview techniques, shows that alien-human hybrids are engaged in a covert program of infiltration into human society, possibly with the final goal of taking over Earth. He claims that some of his research subjects are teaching these hybrids how to blend into human society in order to be indistinguishable from humans, and that this is a worldwide phenomenon.
He generally rebuts critics by calling them “positivists”, since they don’t take Jacobs’s heavily and positively interpreted anecdotes as conclusive evidence (Michael Shermer, for instance). To explain away more substantial parts where his results differ from others’ (i.e. where it is not only a matter of interpreting the data, but the actual data), Jacobs has explained that elements not matching his own perspective are what he terms “confabulations” that he is uniquely poised to recognize and reveal as false by repeatedly questioning the abductee until their recollection changes to be in line with what he, pre-investigation, suspected to find. Duh. Carl Sagan, for instance, has pointed out that Jacobs’s methodology is flawed.
Diagnosis: Crazy old dude. Some people take him seriously, though it is hard to imagine him doing overly much damage except to his interviewees.