Now I wonder if an experiment it did in the mid-1970s is being passed around the hygienist world.
What I did was wonder why hygienists would comment on the state of my teeth (gums tender, bleeding and plaque build-up) when I knew that the only thing effecting my teeth's appearance was what I did recently. So I ran a test on the several hygienists in the dental office I went to.
The test was simple. Over several years, with four cleanings a year, I would alternate (a) vigorous cleaning for all four months, (b) virtually no cleaning and (c) vigorous cleaning for the last two weeks before the cleaning appointment.
All the hygienists were accurate in distinguishing (a) and (c) from (b), the no significant cleaning option. But none could tell the difference between (a) and (c). I never told the hygienists but I've told my dentists and several of my friends.
I think word of my experiment has gotten back to the world of hygienists.