Dual process persuasion theory holds that Other Guys when High WATT and hit the Central Route, they may follow one of two sub-routes, Objective or Biased. Objective processors seek Arguments, engage the Long Conversation in the Head, and change. Biased processors also seek Arguments, but they then cut them to fit a pre-existing pattern (belief, value, schema, stereotype, training), before they engage the Long Conversation. Consider this graphic to illustrate the visual footprint difference.

Obj and Biased ELM Diagrams

The left panel shows the increasing impact of Argument Quality as WATTage increases. Other Guys see the difference between strong and weak. Now the right panel shows Biased Processing. In this example, the Bias serves to process a weak Argument more favorably compared to an Objective Processor. These panels display the theory. Now, let’s look at practice.

Begin with the method.

We used the National Ambulatory Medical Care Survey to examine the use of PSA testing in 2010 (conducted between December 28, 2009, and December 26, 2010) and 2012 (conducted between December 28, 2011, and December 26, 2012). The National Ambulatory Medical Care Survey is an annual, nationally representative survey of ambulatory care in the United States that collects information about outpatient physician visits, patient demographics, diagnoses, medications, and indications for consultation. Specialty of health care professionals was dichotomized as urologist and PCP (general and family practice and internal medicine).

While the TACT is recommending a PSA test to screen men for prostate cancer, the crucial variable is time. Between 2010 and 2012, a scientific task force evaluated the best available scientific information and recommended against PSA testing as normal practice. The quote also reveals two different kinds of medicos who might react to this task force recommendation: Urologists or primary care physicians. The experts here are the urologists who specialize in these matters. The interesting persuasion question is how do these different physicians react to the task force PSA guidelines.

[Expert PSA Sidebar.] The task force, which functions much like a jury, is given all the scientific evidence on an issue, then they argue among themselves and agree to consensus recommendations. After evaluating that evidence the task force concluded that prostate screening was over-used and led to significant errors, misdiagnoses, and harms. They recommended that PSA screening be used only highly specific and constrained conditions rather than as a standard of care. [End of Expert PSA Sidebar.]

In persuasion concepts, the Argument has changed from screening men as a standard to screening men under restricted conditions. The net effect of this recommendation is that considerable fewer men should be screened. Furthermore, given that this is based on all the available scientific evidence, we are talking about strong Arguments. This is the good stuff. By persuasion theory, if you are an Objective processor, these strong Arguments should lead you to recommend fewer screening tests. But, what if you are an expert who is smarter than any stinkin’ task force?

To test that difference, the researchers compared PSA recommendations over time between primary care physicians (less expert) and urologists (more expert). Count the change.

The use of PSA testing decreased from 36.5% to 16.4% among PCP visits . . . whereas it decreased from 38.7% to 34.5% among urologist visits.

As an odds ratio, the difference is amazing. Primary care physicians dropped obviously; the odds ratio is .44 or reversed in the more standard way of thinking, changed to 2.72. With the odds ratio, 2.50 is a Medium Windowpane, an obvious and practical difference. Primary care physicians truly changed their recommendations and arguably because of the task force guidelines. Urologists, by contrast, dropped some, a ratio of .89 (or 1.12 with the more standard way of thinking). A Small ratio is 1.50, so this is a barely detectable difference.

If you look again at my theory graphs and focus on the right hand side of each fan for Objective and Biased Processing, these living Local results exactly mirror the theory predictions. Yeah, the experts did decrease, but not nearly the same as Other Guys physicians who should be pretty smart themselves. The difference in this example is not the intelligence, experience, or credential, but the expert Bias. Urologists suffer with the new recommendations. A primary source of their business comes from providing service to men about prostate problems. If you decrease the use of screening tests, you decrease their business. The bias is apparent.

With primary care physicians, this particular Argument does not materially affect their work. They still see many other people with many other problems that have nothing to do with male prostate issues. These physicians have less bias in their expertise (and income) and can look at the task force recommendations with greater objectivity.

Let’s get out of here with both the science and the persuasion. Science says that medical screening tests are not nearly as useful as once believed. The research literature has accumulated more and better evidence that proves screening as a standard for all Other Guys is dangerous, expensive, and harmful. Persuasion, however, says, that when I’m an expert looking at evidence that threatens my work, I’ll find scissors to cut that data to fit my existing training, experience, and profit.

Zavaski ME, Meyer CP, Sammon JD, et al. Differences in Prostate-Specific Antigen Testing Among Urologists and Primary Care Physicians Following the 2012 USPSTF Recommendations. JAMA Intern Med. Published online February 08, 2016.