We depend on scientific studies to provide us with valid information on so many different aspects of life … it’d be nice to know that the results of those studies actually hold up to scrutiny:
One of the bedrock assumptions of science is that for a study’s results to be valid, other researchers should be able to reproduce the study and reach the same conclusions. The ability to successfully reproduce a study and find the same results is, as much as anything, how we know that its findings are true, rather than a one-off result.
This seems obvious, but in practice, a lot more work goes into original studies designed to create interesting conclusions than into the rather less interesting work of reproducing studies that have already been done to see whether their results hold up.
Everyone wants to be part of the effort to identify new and interesting results, not the more mundane (and yet potentially career-endangering) work of reproducing the results of older studies:
Why is psychology research (and, it seems likely, social science research generally) so stuffed with dubious results? Let me suggest three likely reasons:
A bias towards research that is not only new but interesting: An interesting, counterintuitive finding that appears to come from good, solid scientific investigation gets a researcher more media coverage, more attention, more fame both inside and outside of the field. A boring and obvious result, or no result, on the other hand, even if investigated honestly and rigorously, usually does little for a researcher’s reputation. The career path for academic researchers, especially in social science, is paved with interesting but hard to replicate findings. (In a clever way, the Reproducibility Project gets around this issue by coming up with the really interesting result that lots of psychology studies have problems.)
An institutional bias against checking the work of others: This is the flipside of the first factor: Senior social science researchers often actively warn their younger colleagues — who are in many cases the best positioned to check older work—against investigating the work of established members of the field. As one psychology professor from the University of Southern California grouses to the Times, “There’s no doubt replication is important, but it’s often just an attack, a vigilante exercise.”
Small, unrepresentative sample sizes: In general, social science experiments tend to work with fairly small sample sizes — often just a few dozen people who are meant to stand in for everyone else. Researchers often have a hard time putting together truly representative samples, so they work with subjects they can access, which in a lot of cases means college students.
A couple of years ago, I linked to a story about the problem of using western university students as the default source of your statistical sample for psychological and sociological studies:
A notion that’s popped up several times in the last couple of months is that the easy access to willing test subjects (university students) introduces a strong bias to a lot of the tests, yet until recently the majority of studies disregarded the possibility that their test results were unrepresentative of the general population.