Phenomenon: A live crab, when slowly boiled, will not climb out of the pot.

This is an analog of a known feature in human cognition: humans are not good at observing small changes. We are good at noticing sharp changes.

In this post, I outline a few anecdotal examples. Then, the phenomenon is applied to outside view, why being yourself in dating can backfire, and slowly deteriorating relationships.


Example of Boiling the Crab: Disappearing the Statue of Liberty: A magic trick.

There's a famous David Copperfield magic trick that involves disappearing the statue of liberty before a live audience. The magician closes the curtain, behind which the statue of liberty sits. When the curtain is lifted, the audience is amazed to find the staute of liberty no longer there! The mechanic behind this magic trick is simple: the participants are sitting on a rotating platform, which accelerates below the the audience's sensory threshold. (Source: Poor Charlie's Almanack, by Charlie Munger).

Example of Boiling the Crab: The smell of leaking gas, and a failure of olfactory perception.

A friend of mine named Robert was sitting doing his homework next to the kitchen in the University dormitory. As he was working, someone turned on the gas stove without turning on the flame.

About half an hour later, friend Alex ran into the kitchen, and said: "Holy shit! That gas smell is so strong that I could smell it from the opposite end of the dormitory."

Robert replied: "What gas smell?"


Application: Outside View can observe sharp differences.

An organization, community, or company that lacks outside view may make a series of small changes to their culture, intentional or otherwise. An outsider who comes in will say:

"What the hell?"

Then they point out 10 things that are unusual. Those things may not be bad -- they juts fall outside of normal boundaries.

In this model, the insider is subject to a sequence of small changes from Beginning to End (the boiling crab). The outsider notices the sharp difference, and reacts.

Application: Dating, and being accepted for who you are, is non-automatic. Epistemic Status: Highly conjectural.

"I want to find a girl/boy/other who accepts me for who I am." - a common sentiment.
"Whenever I apply more filters on myself, girls/boys/others that I am interested in gravitate towards me. When I apply fewer filters, my relationships do not last."
"Girls / boys / others don't seem to like it when I'm just being myself."

Many people have traits that are fairly unique, and not found among many other people. Examples might be: shyness in meetups or gt, being transgendered post-op, or posessing speaking quirks from a tight-knit group of friends.

Someone outside one's social circle and/or set of cultural influences will find differences with themselves apparent. In most new social settings, the background for such differences is not transparent. This can cause a feeling of social-mismatch, even if you were (theoretically) extremely compatible as friends or lovers.

Actionable: Boil the crab ;).

Application: A Deteriorating Relationship, and why one of my friend didn't get out of one in time.

A male friend of mine got in a promising new relationship. At first, things were light, passionate, happy, relaxed, and fun.

Two years later, their relationship ended. Mistrust had been building for some time, mostly around my friend's relationships with his other exes. While it was happening, he did not notice. When he looked back, it was obvious things had been falling apart for quite some time.

I was present when he told his story to a less relationship-experienced friend, and she said:

"I would have left that relationship ages ago if I were you. What were you doing?"

Their mutual conclusion: The two friends concluded, as to why he stayed in: The slow boiled crab doesn't noticed. She thought she would not get into that situation: the fast-boiled crab jumps out of the water. My friends' conclusion about the relationship (and the second friend's reaction to it) inspired this post.

There is no claim that all unhappy relationships can be categorized this way :)


I think a lot more falls under this umbrella. Can you think of any time that things happened to you so slowly, that you never noticed until you took a step back?

(For me, norms from academia have started seeping into how I think. For example, I recently became much more concerned about academic status, to the point where it was interfering wiht my happiness. However, I didn't notice when this happened.)

Boiling has a negative connotation, but the concept also applies to positive changes.

Future work:

1) "Uncanny valley" is one tell for small differences that are not actively conscious, but trigger one's internal feelings of difference. Example uncanny face: (courtesy

Feels wrong, man.

A powerful feeling. Absent uncanny valley, an entire slew of changes could occur unnoticed. A predictive or evolutionary explanation for uncanny valley would be much appreciated.

2) "The human mind treats a new idea the same way the body treats a strange protein; it rejects it."

P. B. Medawar

This quote headlines Ralph Merkle's essay on Public Key Cryptography and its societal reaction. The essay is here: Merkle is the director of Alcor cryonics and co-inventor of Public Key Cryptography (PKC).

(This page also contains the most brilliant theoretical computer science idea I've ever seen, which is outlined in his first paper on PKC.)

The P.B. Medawar concept feels related to crab boiling. Sharp changes cause immunal responses. Changes that occur below the sensory threshold do not. I believe sharp changes can also cause certain big updates, which may be harder for slow changes to do. It would be great to have a predictive theory for how communities or people take in slow changes. Perhaps even a book, like: Updating Fast and Slow. :)


Afternote: This is a fresh take on an old concept, which I first read about in Poor Charlie's Almanack. The new pieces are the applications, which developed from a university discussion of how people end up in unhappy relationships without realizing. It was synthesized through a combination of different people's personal experiences.

Apologies if this content is already somewhere on this site. I haven't yet had the attentional bandwidth to look through. At the least, it can be viewed as a fresh take on a familiar idea :)

The discerning reader will find problems in each of the anecdotes and applications. More on this concept can be found in Poor Charlie's Almanack, by Charlie Munger -- a very excellent and underrated book. He calls it boiling the frog, but the principle is te same.

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9 comments, sorted by Click to highlight new comments since: Today at 12:25 AM

Is the "crab boiling" metaphor substantially different from the traditional "frog boiling" metaphor?

I've heard the frog version over and over since I was a child, and I've also heard that it is not experimentally verified.

Like... frogs do, in fact, try to escape objectively hot water when there are low barriers to exit. A good biology keyword for research on the clade-spanning mechanism(s) involved here is the "thermal critical maximum". There is a whole family of proteins for "responding to stress by paying more attention to folding or re-folding proteins" all the way down at the bacterial level, and the whole family is named for the first kind of stress response discovered: the stress response to heat.

Your post initially made me wonder if real crabs (whose recent evolution may have lacked really big temperature swings because of oceanic temperature buffering somehow?) might live up to the metaphor's implications better than real frogs (that are fresh water ectotherms whose entire life sorta revolves around leveraging their environment to control their internal state, with temperature being near the top of the list), but casual googling suggests that (warning: disturbing video) crabs also flee hot pans.

An uncharitable reading is that crabs are a better metaphor simply because they "seem more convincing" because it there has been less time for the crab version to have been debunked?

Frog experts perrenially get questions about this, because the meme refuses to die, and in their responses they sometimes note that the typical spreaders of the frog meme are individuals like business consultants, political activists, and religious preachers. When I squint and put on my cynic hat, this reads to me basically as "people who specialize in personally benefiting from tricking entire groups of people into doing things that often don't make a lot of sense".

Despite the fundamental dishonesty, if the frog metaphor was accepted by the audience, it could be a rhetorically solid part of a larger process of achieving group compliance for nearly arbitrary changes.

Basically, the frog metaphor encourages people to distrust their own ability to think objectively about how the world works now, or how it has worked in the past, and in the face of this uncertainty it offers the idea that a large but unmeasurable and essentially invisible harm can be avoided by doing... something... anything? It depends on the situation.

If there was a genuine large imminent loss (like dying from hyperthermia) then many dramatic changes might be justified to attempt to avoid this outcome. Run! Jump! Pull levers at random! Thus, a boiling frog metaphor, deployed with no "kicker" attached, is a slightly confusing thing...

One naturally wonders when the other shoe will drop and the speaker will reveal their claimed harm and propose a more specific plan...

...basically I'm wondering where you're going with this ;-)

This is a good point. I anecdotally hear that crabs don't do this from my parents who cooked crabs, but this may be suspect due to memory issues on my part. If I am understanding correctly, the major objection your comment brings up is: this article presents a faulty anecdote and a 'lesson' that can be abused by the speaker. And that is dangerous.

In particular, I think you are referring to speakers who do misuse the metaphor to achieve group compliance. I agree this seems possible, and I respect your experience with it. Thus, I agree that there is a phenomenon at play here that can be misused.

Anyhow, I like to attach " The discerning reader will find problems in each of the anecdotes and applications. " at the end of my writings, in order to ameliorate the effects you mention -- you will notice it on the original article. Perhaps this doesn't actually achieve the right ends of encouraging skepticism and cynicism, hohwever.

Thank you for bringing this up. I will check my anecdotes more carefully next time (I did check this one on Googling, but hearsay from people who have cooked crabs in the past led me to believe the initial title was solid enough to post.) In due time, I will edit this post to reflect your thoughts :).

Your post is useful, and also very well written and structured to the point that there isn't much left to comment on. I'm leaving this comment as a way to give more specific encouragement than just upvoting.

Abstract instances of the crab-boiling effect can arise from changes that are above the sensory threshold. All that's necessary is for acclimatization to outpace innovation. Each individual step (and these abstract instances are often stepwise rather than continuous) can still register as weird, but if you get used to it before the next step happens, your 'weirdness threshold' doesn't continuously increase.

We've all seen Back to the Future, right? In 1955, Ronald Reagan was a supporting actor who'd just become the host of something called "General Electric Theater". His only political experience was as a former president of the Screen Actors Guild, and he wasn't even a Republican yet. The progression from there wasn't terribly weird: he quit working for GE to become more politically involved, campaigned against Medicare in 1961 and for Goldwater in 1964, boosted his profile enough on the Goldwater campaign that he ran for governor of California and won, tried to primary Gerald Ford and lost, and won against Carter in 1980.

Reagan's rise to the presidency is stepwise, and each step is above the sensory threshold, but you still get the crab-boiling effect in the end.

I have heard the boiling crab before, but I've never thought to apply it to a community. I almost feel as though we should have one day a year where we try to evaluate ourselves with fresh eyes and try to imagine how things would appear to an outsider. We could also ask ourselves if we'd really choose to set things up the same way if we were starting fresh. In fact, I'd probably try to start this tradition if I had more social capital.

This sounds like the idea that is good in theory, but difficult to implement in practice.

I am not too familiar with the community, but my understanding is that most communities 'drift' into what they are, often by happenstance: not much is a conscious choice.

For example, it is well documented that people tend to live in communities and have friend groups that are ethnically similar to themselves. (Example: Nicky Case's Parable of the Polygons. Few people consciously choose to do this. It happens when people follow their feelings on what groups make them feel comfortable and at home. You can think of this as gradient descent.

As such, it seems like "choosing to set things up in the same way" is a bit of a mis-classification. I would guess that most properties of the community you are referring to, which I am not familiar with, occurred due to the individuals within the collective following what felt right to them at the time. I would imagine only a few core bits were consciously decided on.

Here, I may be very wrong. I'm not familiar with the 'we' you are referring to, and who that does and does not cover :). (Is it LesserWrong? Or is it some broader umbrella).

Excellent post! I think the positive direction of boiling the crab deserves more emphasis. A lot of habits have slow, accumulating returns that are below our sensory threshold but still worth sticking to, and just as people are unreasonably hesitant to abandon slowly deteriorating things, we are unreasonably willing to give up slowly improving things. I sense that a primary difficulty with diets is that their effects take several months and the changes are too gradual for people to notice.

Hmmm, that may be the case on diets. Positive changes below the sensory threshold. Maybe you can write a post on it :).

There is a heuristic I have heard about PhD studies. A capable mathematics professor once told me: a graduate student should feel like s/he is making progress every day. Even if no new resullts are forthcoming. Experimentally, this is possible, and leads to improved happinness and better results. I am part of the academic system, so my anecdotes are biased in that direction.

I wonder if diets where you can feel improvement every day, work better. Some friends partake in keto, vegetarian, low-carbohydrate, soylent, and/or paleo. A subset of these dieters tell me, through enthusiastic blog post or private message, how amazing their new diet makes them feel, and how much more daily energy and diligence they have. I have not done a systematic study of whether this makes them stick to the diet for longer. For the critically dehydrated, half of China for instance, I have anecdotally heard that drinking 3-5 glasses of water a day has the same effect.

(There is another common probem I have observed with diets, that has nothing to do with slow-boiling. Some people get results fast, and then ditch their diet to eat ice cream.)

Maybe ignoring small changes should be in a generic list of cognitive biases, maybe it already is. I wonder to what extent measuring and logging things can help overcome this.

Also, there seems to be a moral difference between slow change and fast change. For example, evolution, as it happens over thousands of years is seen as a good thing, but if your children were totally different from you, it would be seen as a problem. Same is true for cultural changes too.