This week’s Skeptic’s Guide to the Universe features a discussion (starting at 38:20) of the claims made by Architects and Engineers for 9/11 Truth. A&E9/11Truth is a conspiracist organisation whose main argument is that the collapse of the three World Trade Center towers could only have been caused by controlled demolition. An email is read asking “can you… honestly say that there is absolutely nothing interesting or suspicious about the manner in which all of the towers, but specifically WTC7, came crumbling down.” The panel offers cursory rebuttals of the main claims, noting that each point has already been covered in detail by people with legitimate expertise in the relevant subjects. The discussion turns towards the psychology of conspiracy theorising, pointing out that A&E9/11Truth’s claims are an example of anomaly hunting – combing through every eyewitness account, news report, photograph, video, official report etc about the events of 9/11, and seizing upon any piece of information that doesn’t immediately appear to fit with the generally accepted narrative. These small pieces of errant data are framed as being curious and sinister, with the implication that they provide evidence of a conspiracy.
Anomaly hunting is not unique to 9/11 conspiracy theories; it is characteristic of all conspiracy theories. Philosopher Brian Keeley argues that the reliance on errant data gives conspiracy theories an appearance of explanatory strength; the conspiracy theory is apparently able to account for everything explained by the mainstream narrative, plus all the anomalies and errant data which appear to go against the mainstream account. Yet this superior explanatory strength is an illusion. Under scrutiny, the leap from anomalies and errant data to a coherent alternative conspiratorial narrative is unjustified – the anomalies so crucial to conspiracy theories are not satisfactory evidence.
This feature of conspiracy theories is, in part, a product of the confirmation bias. The idea that a conspiracy took place is the starting point; any evidence that can be shoe-horned to fit with that theory is incorporated and any evidence that doesn’t fit is dismissed, distorted or ignored. In the case of A&E9/11Truth, anything that appears to support the hypothesis that the collapses were a result of controlled demolition is accepted uncritically, and everything else is disregarded. But conspiracy theorists aren’t the only ones who are susceptible to the confirmation bias; we all are. John McHoskey looked at biased evaluation of evidence in relation to J.F.K. conspiracy theories (full-text paywalled). Both believers and skeptics selectively accepted or dismissed pieces of evidence to fit with their preexisting point of view. Confirmation bias is unavoidable; it’s part of being human. To overcome it requires a conscious effort to let our beliefs be shaped by the evidence, rather than shaping the evidence to fit with our beliefs.