Evidence Shmevidence

I just logged in after a long absence and I have 13 comments! I'm famous! I'll go through those soon and get them posted, but in the meantime ...

I was reading an article on herbal remedies in Parade magazine today (the one that comes with the Sunday paper) and saw a section on Ginkgo biloba. Ginkgo is a tree that we have a lot of on the Fresno State campus. It has funny fan shaped leaves that turn bright yellow in the fall. Anyway, the section on ginkgo contains two interesting sentences. The first says, "Evidence suggests that ginkgo biloba has a positive effect on the vascular system ...." The second says, "Some doctors recommend it to boost memory ...."

One way to read this is that 1) ginkgo has a positive effect on the vascular system and 2) ginkgo boosts memory. The different wordings--"evidence suggests" versus "some doctors recommend"--might be just for the sake of variety. But I don't think this is the case. The reason is that while there may be scientific evidence that ginkgo has positive effects on the vascular system, the best current evidence is that it does not boost memory. So although it cannot truthfully be said that "evidence suggests" that it works, it can be said that "some doctors recommend" it. The change in wording shifts responsibility for what is essentially a false statement onto those unnamed doctors, while still generating positive interest in ginkgo.

Although the average person might not even notice the "evidence suggests" versus "some doctors recommend" difference, I maintain that this is exactly the kind of thing that psychology majors should be learning to notice. There is a huge difference between knowledge based on empirical evidence and "knowledge" based on opinion--even expert opinion. This is especially true in psychology where we have lots of scientific knowledge about the diagnosis and treatment of mental disorders, but we also have people (with Ph.D.s, no less) who claim they will hypnotize you and take you back to your past lives to identify the traumatic experiences that are causing your current psychological problems.

"Some psychologists recommend ..." should definitely put you on guard.