Abandoning Strong Priors

In a delightful post recently on the true meaning of "derp", Noah Smith utilizes a little side trip down a Bayesian probability theory lane to illustrate his answer.

In so doing he also illustrated a term that is new (for me): strong priors.  As Smith puts it "What does it mean for a prior to be strong?  It means you really, really believe something to be true.  If you start off with a very strong prior, even solid evidence to the contrary won't change your mind."

Sigh.

There are several strong priors I have spent decades basing behaviors upon and as it turns out?  They simply are not true.

Knowing they are not true should then alter my behaviors to reflect my new knowledge, correct?  I mean, that would be the only rational response.

And yet, and yet.  I often find myself struggling not to allow my previous behaviors to snap back into place simply because my priors were so strong.  In other words, despite what I know to be true, I keep wanting to behave according to what I used to THINK was true, even though I now know better.

Two simple examples?

The first occurs in the realm of some of my most firmly held beliefs - the kitchen.  It concerns the proper manner of loading the dishwasher.

For nearly all my dishwasher loading years I always, ALWAYS loaded cutlery in their handy little baskets with the handles sticking UP.  I'm not sure how that tendency evolved, but I'm guessing now it was my mother's way of protecting our younger hands from fork and knife points as my brother and I loaded and unloaded the dishwasher for her.

At some point her safety precaution morphed from a practical way to avoid injuries in her offspring to written-in-stone type law.  Thou shalt not load the cutlery handles down.  Like that.

So even after my husband carefully read the manual for our dishwasher when it was new, and explained to me the manufacturer was very clear on how the cutlery was supposed to go into the machine?

I argued with him that he must have misunderstood.  He probably misread.  That simply couldn't be the case.

Why?  Because, that's why.  Everybody knows you load the cutlery handles up.  EVERY. Body.

As it turns out, cutlery is supposed to be loaded handles down.  Why?  Simple -  so the messy mouthy eaty parts are exposed to the most possible washing action from the machine.  It makes perfect sense and yet to this day I find myself having to stop and reload bundles of cutlery that I mindlessly just popped into the basket with the handles sticking up.

Do I have any other deeply cherished beliefs that turn out to be wrongheaded?

Oh, do I ever.

Next up for disabuse was the idea that if you water a plant during the day and get even a single drop of water on the leaves? That water drop will act like a magnifying glass and severely sunburn the poor defenseless plant.

All along I resisted watering even the thirstiest droopiest plants until after sundown in order to reduce the risk of splashing water on the foliage.  But I went past that - I taught that particular stricture to my kids and even argued with my husband about it when he sensibly challenged my assertion.  When he said he'd change his during-the-day-going-to-ruin-everything misbegotten watering ways only if I could prove to him that there was any basis in my conviction?  I confidently did some checking around.

Ooops.  Turns out established plants aren't all that easily sunburned (with the possible exception of one just moved into a full sun situation from deep shade) even with the presence of water droplets on the foliage.  Now there may be other reasons not to get water on the leaves of a plant, but they have nothing to do with sunburn.  Period.

It reminds me of the story of a recipe that included instructions to "cut off both ends of the roast before placing into pan".  The recipe was well beloved, handed down in a family for generations and had been faithfully followed for the better part of a century before an inexperienced cook questioned, "why?".

Nobody knew why - they'd been following the recipe and it was always delicious.  The question was finally put to the oldest cook in the group. She explained it was because the originator of the recipe had a very small roasting pan and always had to cut the meat to fit.

Strong priors.  I'm afraid I've only begun to scratch the surface of all the ways I'm slavishly behaving according to deeply held beliefs that have no basis in fact.  I'm the stubborn type for reals but I'm determined now to take a closer look to assure at least some of that stubbornicity claims some basis in fact.

Because, that's why.