Consider the tourist brochures used by countries to advertise their wares: you can expect that the pictures presented to you will look much, much better than anything you will encounter in the place. And the bias, the difference (for which humans correct, thanks to common sense), can be measured as the country shown in the tourist brochure minus the country seen with your naked eyes. That difference can be small, or large. We also make such corrections with commercial products, not overly trusting advertising. But we don't correct for the difference in science, medicine, and mathematics, for the same reasons we didn't pay attention to iatrogenics. We are suckers for the sophisticated.