Wednesday, January 29, 2014

Doing it right is least optimal!

This surprising fact is almost forced logically....

For most things in life we have decreasing marginal utility, that is the more we use, the less valuable it is (the last bite of the icecream is vastly less exciting than the first one etc.)

Similarly, most processes also have diminishing marginal U. Most benefit from exercise is by doing the first little bit (not being sedentary). Ten minutes of social interaction give the most benefit of not feeling lonely, while the rest is nearly useless.

Now to my toothbrushing that made me realize this point.
The "right way" to brush is clearly to twice daily, 3 minutes brushing + floss.

But if I brush once a week for one minute, the effect of this brushing will be five times stronger than the last minute of my seventh day brush. Because this superficial weekly one will remove most dir in a minute, while the effect of every minute in "doing it right" is much lower.

The idea is that the more throughout and "right" you do something, the lower the value of each point of time used.

Now brushing? the second minute per week will still be hugely valuable, even if much less than the first minute. and so on. But the twice daily 3 minutes will have the lowest per minute effect.

Ouch, for "doing it right"


Anonymous said...

There is a cost for doing it right.
There is a higher cost for doing it wrong.
The thing is that doing it right involves self-control while doing it wrong involves a different kind of control which may even involve others covering the costs. Yea when cleaning up the subtler finer particles may require more work than the coarser ones... never the less one may require to get rid of them both...

Jazi Zilber said...

Actual teeth brushing was never the subject. The idea is that the first minute is ten times more crucial than the third minute of brushing "correctly". It is about usefulness in degrees of doing something. Not about mouth cleaning per se and its context at all.

When others pay the cost, it isanother subject altoghether

Anonymous said...

>Actual teeth brushing was never the subject.

But since you used it to illustrate your point, pointing out a fallacy in your example is informative.

I know of kids who have teeth damage. They brushed every day, but they drank something before bedtime (I forget if it was sugary or milk) without brushing afterwards. It's not just a matter of removing dirt from teeth, the goal is to prevent bacteria from damaging the teeth over time.

That's anecdotal, but my point is, the simplistic measure "brushing effect per minute" contains assumptions that drastically effect the outcome if you try to maximize it. This is a classic problem in optimization: choosing what function to optimize is tricky.

Your overall point is interesting, and I enjoyed reading it.

Daniel Kampner said...

I find your thoughts very insightful.
For some things in life - we indeed are exited only at the beginning quickly lose interest. For other things it is that last finishing touch that makes all the difference!
(like spending weeks preparing a business proposal but failing to send it in!)
Most people's life experience teaches them that doing things right is overall a good policy - and that once you develop a habit of skimping - you are on a slippery slope of cutting corners that can be a disaster. On the other hand I like your thinking out of the box attitude!

Jazi Zilber said...

Definitely, Daniel.

I am giving an idea. Not arguing for acting stupid........ Acting rational is smart. Of course