Guard against Anchoring and Confirmation Biases

I just came across two interesting articles that deal with bias in forming opinions and beliefs. It's a basic tenet of DRE training that an opinion should not be reached until the evaluation has been completed. Further, the DRE's opinion must be based on the totality of the the evaluation (and of the entire investigation for that matter).

The October 15, 2011 issue of Bottom Line/Personal contained a front page article about misdiagnoses in medicine. It struck me that DRE's face many of the same issues and challenges that medical doctors do in reaching opinions. According to the article, "Doctors routinely take a mental shortcut known as 'anchoring.' They quickly latch onto an idea about what's causing your symptoms." "Anchoring" is definitely something that DRE's have to guard against. For example, anchoring may be caused by what the arrestee says he/she has taken (true or not), what the arresting officer believes the person is under the influence of, or the substances and paraphernalia that were in the arrestee's possession. Guard against "anchoring" by asking yourself whether something else, including a medical condition, may be causing the signs and symptoms. Continually challenge yourself by asking yourself if there are alternative explanations. (As an aside, the article says that in US autopsy studies, "doctors misdiagnosed illnesses between 20% and 40% of the time.")

The July issue of Scientific American contained a column by Michael Shermer titled "The Believing Brain." Shermer wrote that "anchoring bias" occurs when one relies too heavily on one piece of information to make a decision. A DRE who decides that a person is under the influence of, say cannabis, because the person had bloodshot eyes, is an example of "anchoring bias." Shermer also writes about another type of relevant bias called "confirmation bias," in which one seeks and finds "confirming evidence in support of already existing beliefs and ignoring or reinterpreting disconfirming evidence." Sort of like reaching an opinion first, and then gathering evidence to support the opinion.

The best defense against bias in your DRE opinions is to continually remind yourself that there could be alternative explanations for each sign and symptom, and to not reach a final opinion until the entire evaluation has been completed.