Deciding when to stop your quest for the ideal apartment, or ideal spouse, 
depends entirely on how long you expect to be looking, says Brian Christian.  
The first one you check will be the best you’ve seen, but it’s unlikely to be 
the best you’ll ever see.  So you keep looking and keep finding new bests, 
though ever less frequently, and you start to wonder if maybe you refused the 
very best you’ll ever find.  And the search is wearing you down.  When should 
you take the leap and look no further?

The answer from computer science is precise: 37% of the way through your search 
period.  If you’re spending a month looking for an apartment, you should 
calibrate (and be sorely tempted) for 11 days, and then you should grab the 
next best-of-all you find.  Likewise with the search for a mate.  If you’re 
looking from, say, age 18 to 40, the time to shift from browsing and having fun 
to getting serious and proposing is at age 26.1.  (However, if you’re getting 
lots of refusals, “propose early and often” from age 23.5.  Or, if you can 
always go back to an earlier prospect, you could carry on surveying to age 

This “Optimal Stopping” is one of twelve subjects examined in Christian’s (and 
co-author Tom Griffiths’) book, Algorithms to Live By.  (The other subjects 
are: Explore/Exploit; Sorting; Caching; Scheduling; Bayes‘ Rule; Overfitting; 
Relaxation; Randomness; Networking; Game Theory; and Computational Kindness.  
An instance of Bayes’ Rule, called the Copernican Principle, lets you predict 
how long something of unknown lifespan will last into the future by assuming 
you’re looking at the middle of its duration—hence the USA, now 241 years old, 
might be expected to last through 2257.)

Christian went into detail on the Explore/Exploit problem.  Optimistic research 
minimizes later regret.  You’ve found some restaurants you really like.  How 
often should you exploit that knowledge for a guaranteed good meal, and how 
often should you optimistically take a chance and explore new places to eat?  
The answer, again, depends partly on the interval of time involved.  When 
you’re new in town, explore like mad.  If you’re about to leave a city, stick 
with the known favorites.

Infants with 80 years ahead are pure exploration— they try tasting everything.  
Old people, drawing on 70 years of experience, have every reason to pare the 
friends they want to spend time with down to a favored few.  The joy of the 
young is discovering.  The joy of the old is relishing.

                                                        —Stewart Brand <>

[A linkable, illustrated version of this summary is here 
 on Medium.]

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