One common type of bias stems from an uncomfortable reality in the scientific culture. Researchers have a continual need to publish articles in journals, in order to sustain their reputations and rise in academia. That publish-or-perish mentality might exert an influence upon the outcomes of hypotheses, because as one critic notes, academia tends to bias toward statistically significant, "positive" results [source: van Hilten].
Indeed, meta-analyses show that journals are much more likely to publish studies that report a statistically significant positive result than ones that don't. Publication bias is stronger in some fields than others; one 2010 study found that papers in the social sciences are 2.3 times more likely to show positive results than papers in the physical sciences [source: Fanelli].
As Ian Roberts, a professor of epidemiology and public health at the London School of Hygiene and Tropical Medicine, noted in a 2015 essay, clinical trials showing that a treatment works are much more likely to be published than those showing that it doesn't have any benefit or even harmful.