A decade ago, Robin Hanson introduced me to the metaphor of the “monkey trap”:

It is said you can trap a monkey by putting a nut through a small hole
in a gourd. The monkey reaches in and grabs the nut, but then his fist
won’t fit back through the hole. Greedy monkeys will literally let
themselves be caught rather than let go of the nut.

Robin had a specific monkey trap in mind: medical spending.  Robin says we can drastically reduce medical spending without hurting health, so we should drastically reduce medical spending.  His critics often seem to agree about the effects of spending cuts, but refuse to endorse them nonetheless.  Robin says they should.

So far, no
commenter on my essay seems willing to let go of the nut of effective
medicine, held in the gourd of the second half of medical spending.

As an analogy, imagine you ran a software company, whose many offices
had different wage levels and work cultures, with average work hours
ranging from seven to fourteen per day. Surprised to see these offices
were equally productive, you randomly changed wages, inducing changes in
work hours. You again found offices that worked more did not produce
more; after seven hours people got tired and added as many bugs as they
fixed. If instead of just cutting wages to get only seven hours of
work, you just told everyone “watch out for bugs,” you would be in a
monkey trap, refusing to let go of the nut of productive work in the
gourd of extra work hours.

I like the idea of the monkey trap.  It’s enlightening and funny.  But to fairly apply it, you must be mindful of three complexities.

1. It only makes sense to invoke the monkey trap if you have good evidence that, on average, the bad outweighs the good.  (Including opportunity costs, of course).  When someone objects, “The good outweighs the bad,” you should dispute the claim, not joke about monkey traps.

2. Suppose you admit that the bad outweighs the good.  The monkey trap is not relevant if you’re willing and able to distinguish good from bad.  After all, even if bad outweighs good by a factor of 10, why not throw away all the bad and keep all the good?

3. Suppose you admit the bad outweighs the good, and you’re currently unable to distinguish good from bad.  However, you have a viable plan to acquire the knowledge you need to distinguish good from bad in the foreseeable future.  Are you stuck in the monkey trap?  Once again, no.  Why throw away the good with the bad if you’ll soon be able to tell the difference?

So who genuinely is stuck in the monkey trap?  Just flip things around.  You’re in the monkey trap if:

1. The bad outweighs the good.


2. You have little ability (or inclination) to distinguish bad from good.


3. You’re unlikely to acquire this ability in the foreseeable future.

By this standard, I think Robin was right to tell his critics that their hands were stuck in the monkey trap.  Despite their numerous intellectual concessions, Robin’s critics rarely claim to know much about wasteful spending – and don’t seem like they’re burning to learn more.  Instead, they want to obstruct the one viable reform on the table: cutting spending.  Why?  Social Desirability Bias is the best explanation.  Whatever the facts, “If we can help just one sick person, we should spend whatever it takes,” sounds vastly better to psychologically normal humans than “Let’s stop wasting taxpayer money.”