Many positive scientific effects published in the literature seem to diminish in their significance with time; this is known as the decline effect. For example, initial parapsychological research indicated evidence for psychic ability, but this effect declined with subsequent studies. Some scientists link this to the strange statistical effect called regression to the mean: the phenomenon that if a variable is extreme on its first measurement, by the second measurement it will be closer to the average. It is impossible to test this, however, without access to negative results of scientific studies.
Most negative results of scientific experiments remain unpublished. This is a pervasive problem the world over, and is likely to be skewing the available scientific data pertaining to certain phenomena. When it turned out Eli Lilly (the makers of antidepressants like Prozac) had withheld the results of about a third of the trials conducted to win government approval, the clinical community was up in arms. Unfortunately, this is par the course for Continue reading “Unpublished results and the decline effect”