Welcome back to the blog. An article published today in JAMA Internal Medicine was just the impetus I needed to return after more than a year.
Hardly a student of medicine who has trained in the past 10 years has not heard of "anchoring bias" or anchoring on a diagnosis. What is this anchoring? Customarily in cognitive psychology, to demonstrate a bias empirically, you design an experiment that shows directional bias in some response, often by introducing an irrelevant (independent) variable e.g., a reference frame, as we did here and here. Alternatively, you could show bias if responses deviate from some known truth value as we did here. What does not pass muster is to simply say "I think there is a bias whereby..." and write an essay about it.
That is what happened 20 years ago when an expository essay by Crosskerry proposed "anchoring" as a bias in medical decision making, which he ostensibly named after the "anchoring and adjustment" heuristic demonstrated by Kahneman and Tversky (K&T) in experiments published in their landmark 1974 Science paper. The contrast between "anchoring to a diagnosis" (A2D) and K&T's anchoring and adjustment (A&A) makes it clear why I bridle so much at the former.
To wit: First, K&T showed A&A via an experiment with an independent (and irrelevant) variable. They had participants in this experiment spin a dial on a wheel with associated numbers, like on the Wheel of Fortune game show. (They did not know that the dial was rigged to land on either 10 or 65.) They were then asked whether the number of African countries that are members of the United Nations was more or less than that number; and then to give their estimate of the number of member countries. The numerical anchors, 10 and 65, biased responses. For the group of participants whose dials landed on 10, their estimates were lower, and for the other group (65), they were higher.
