Occam's Razor and Bayesian Measures of Likelihood Suggest Loch Ness Monsters Are Real Animals

Abstract

Lay Summary—The simplest explanation for all the evidence is that Nessies, the “Monsters” in Loch Ness, are real but as yet unclassified animals — evidence comprising eyewitness reports, sonar results, surface and underwater photography, and surface moving film. The Bayesian approach to estimating probability points to a similar conclusion. If sonar and photographic evidence had preceded rather than followed intense global interest based on eyewitness reports, the existence of Nessies might have become widely accepted rather than disbelieved. This analysis points to the need for public policies about science and medicine to be informed by people who understand how science works, for instance historians of science or individuals versed in the modern discipline of Science & Technology Studies.
 Abstract—Regarding claims of Loch Ness Monsters, what the simplest explanation might be depends on how the evidence is assembled and judged. Taken individually, eyewitness reports can be simply and plausibly explained away as misperceptions and occasional hoaxes. Many of the claimed surface photographs can be simply and plausibly challenged as misleading representations of natural phenomena, and again some deliberate faking. Simple explanations are less readily to hand for the underwater photos and the Dinsdale film, yet disbelievers have offered some. However, when the evidence is taken as a whole, the simplest explanation is that there are real animals responsible for these three or four quite independent types of evidence. A similar conclusion would be reached by considering the evidence sequentially by a Bayesian approach, progressively modifying the estimated likelihood using each independent type of evidence. Loch Ness Monsters might be the sort of premature discovery described by Gunther Stent: the best evidence came too late to influence media attitudes and popular belief. The difficulty of changing long-held views is illustrated not only in this instance but also within science overall, where hegemonic theories have for lengthy periods withstood the accumulation of considerable contradicting facts. Advice to policy makers should come not from practicing scientists but from individuals who know the history of science and understand the many potential pitfalls in advancing knowledge.