The popularity of meta-analysis in parapsychology has been criticized by numerous researchers, and is often seen as troublesome even within parapsychology itself. Critics have said that parapsychologists misuse meta-analysis to create the incorrect impression that statistically significant results have been obtained that indicate the existence of psi phenomena. Physicist Robert Park states that parapsychology's reported positive results are problematic because most such findings are invariably at the margin of statistical significance and that might be explained by a number of confounding effects; Park states that such marginal results are a typical symptom of pathological science as described by Irving Langmuir.