"Expert" Advice From People With Something To Sell

I wrote this to my son and daughter-in-law while they were shopping for a car.

"If an expert has something to gain from his opinion being in a given direction, he is highly likely to hold that opinion, and to attribute it to his expertise."

Here's the part that's hard to believe:

"This is true even when the expert is a decent, compassionate, well-meaning, generally honest, fine person."

I am confident of the truth of this, from vast experience. But there have been two studies, one pretty scholarly, the other more memorable and probably more useful, that back this up.

Study 1: New York Magazine sent people with "backache symptoms" out to experts. They described their symptoms identically to all. The back surgeons all said the person needed back surgery, physical therapists said that they needed physical therapy, etc. etc. (By the way, I believe backache studies show that chiropracty gives relief, exercise gives prevention, and the rest are almost always a bad idea or at best harmless. Even when an MRI shows "structural problems".)

Study 2: The scholarly one. Economists studied the history of house sales of houses owned by regular folks, with a real estate agent, vs. houses owned by the real estate agent himself. It turns out that agents give themselves different, and better, advice than they give their clients (presumably because, if they don't own the house, their interest is in getting the deal closed, much more than in getting the best price).

This is in part why Mom and I try to use university doctors at university hospitals, who are typically employees not paid, or paid much, by the piece.

Anyway, this was kicked off by the XXXXXX advice. I thought you were getting advice from a recommended consultant. Once I heard that he had something to gain, his advice, in my opinion, was less than useless (and I strongly disagree with the advice that a car with unknown background and high miles is a desirable car under any circumstances). Even if he's highly recommended, and has 43 merit badges mostly for helping the elderly and blind cross the street.