A Year of Spaced Repetition Software in the Classroom
Last year, I asked LW for some advice about spaced repetition software (SRS) that might be useful to me as a high school teacher. With said advice came a request to write a follow-up after I had accumulated some experience using SRS in the classroom. This is my report.
Please note that this was not a scientific experiment to determine whether SRS "works." Prior studies are already pretty convincing on this point and I couldn't think of a practical way to run a control group or "blind" myself. What follows is more of an informal debriefing for how I used SRS during the 2014-15 school year, my insights for others who might want to try it, and how the experience is changing how I teach.
Summary
SRS can raise student achievement even with students who won't use the software on their own, and even with frequent disruptions to the study schedule. Gains are most apparent with the already high-performing students, but are also meaningful for the lowest students. Deliberate efforts are needed to get student buy-in, and getting the most out of SRS may require changes in course design.
The software
After looking into various programs, including the game-like Memrise, and even writing my own simple SRS, I ultimately went with Anki for its multi-platform availability, cloud sync, and ease-of-use. I also wanted a program that could act as an impromptu catch-all bin for the 2,000+ cards I would be producing on the fly throughout the year. (Memrise, in contrast, really needs clearly defined units packaged in advance).
The students
I teach 9th and 10th grade English at an above-average suburban American public high school in a below-average state. Mine are the lower "required level" students at a school with high enrollment in honors and Advanced Placement classes. Generally speaking, this means my students are mostly not self-motivated, are only very weakly motivated by grades, and will not do anything school-related outside of class no matter how much it would be in their interest to do so. There are, of course, plenty of exceptions, and my students span an extremely wide range of ability and apathy levels.
The procedure
First, what I did not do. I did not make Anki decks, assign them to my students to study independently, and then quiz them on the content. With honors classes I taught in previous years I think that might have worked, but I know my current students too well. Only about 10% of them would have done it, and the rest would have blamed me for their failing grades—with some justification, in my opinion.
Instead, we did Anki together, as a class, nearly every day.
As initial setup, I created a separate Anki profile for each class period. With a third-party add-on for Anki called Zoom, I enlarged the display font sizes to be clearly legible on the interactive whiteboard at the front of my room.
Nightly, I wrote up cards to reinforce new material and integrated them into the deck in time for the next day's classes. This averaged about 7 new cards per lesson period.These cards came in many varieties, but the three main types were:
- concepts and terms, often with reversed companion cards, sometimes supplemented with "what is this an example of" scenario cards.
- vocabulary, 3 cards per word: word/def, reverse, and fill-in-the-blank example sentence
- grammar, usually in the form of "What change(s), if any, does this sentence need?" Alternative cards had different permutations of the sentence.
Weekly, I updated the deck to the cloud for self-motivated students wishing to study on their own.
Daily, I led each class in an Anki review of new and due cards for an average of 8 minutes per study day, usually as our first activity, at a rate of about 3.5 cards per minute. As each card appeared on the interactive whiteboard, I would read it out loud while students willing to share the answer raised their hands. Depending on the card, I might offer additional time to think before calling on someone to answer. Depending on their answer, and my impressions of the class as a whole, I might elaborate or offer some reminders, mnemonics, etc. I would then quickly poll the class on how they felt about the card by having them show a color by way of a small piece of card-stock divided into green, red, yellow, and white quadrants. Based on my own judgment (informed only partly by the poll), I would choose and press a response button in Anki, determining when we should see that card again.

[Data shown is from one of my five classes. We didn't start using Anki until a couple weeks into the school year.]
Opportunity costs
8 minutes is a significant portion of a 55 minute class period, especially for a teacher like me who fills every one of those minutes. Something had to give. For me, I entirely cut some varieties of written vocab reinforcement, and reduced the time we spent playing the team-based vocab/term review game I wrote for our interactive whiteboards some years ago. To a lesser extent, I also cut back on some oral reading comprehension spot-checks that accompany my whole-class reading sessions. On balance, I think Anki was a much better way to spend the time, but it's complicated. Keep reading.
Whole-class SRS not ideal
Every student is different, and would get the most out of having a personal Anki profile determine when they should see each card. Also, most individuals could study many more cards per minute on their own than we averaged doing it together. (To be fair, a small handful of my students did use the software independently, judging from Ankiweb download stats)
Getting student buy-in
Before we started using SRS I tried to sell my students on it with a heartfelt, over-prepared 20 minute presentation on how it works and the superpowers to be gained from it. It might have been a waste of time. It might have changed someone's life. Hard to say.
As for the daily class review, I induced engagement partly through participation points that were part of the final semester grade, and which students knew I tracked closely. Raising a hand could earn a kind of bonus currency, but was never required—unlike looking up front and showing colors during polls, which I insisted on. When I thought students were just reflexively holding up the same color and zoning out, I would sometimes spot check them on the last card we did and penalize them if warranted.
But because I know my students are not strongly motivated by grades, I think the most important influence was my attitude. I made it a point to really turn up the charm during review and play the part of the engaging game show host. Positive feedback. Coaxing out the lurkers. Keeping that energy up. Being ready to kill and joke about bad cards. Reminding classes how awesome they did on tests and assignments because they knew their Anki stuff.
(This is a good time to point out that the average review time per class period stabilized at about 8 minutes because I tried to end reviews before student engagement tapered off too much, which typically started happening at around the 6-7 minute mark. Occasional short end-of-class reviews mostly account for the difference.)
I also got my students more on the Anki bandwagon by showing them how this was directly linked reduced note-taking requirements. If I could trust that they would remember something through Anki alone, why waste time waiting for them to write it down? They were unlikely to study from those notes anyway. And if they aren't looking down at their paper, they'll be paying more attention to me. I better come up with more cool things to tell them!
Making memories
Everything I had read about spaced repetition suggested it was a great reinforcement tool but not a good way to introduce new material. With that in mind, I tried hard to find or create memorable images, examples, mnemonics, and anecdotes that my Anki cards could become hooks for, and to get those cards into circulation as soon as possible. I even gave this method a mantra: "vivid memory, card ready".
When a student during review raised their hand, gave me a pained look, and said, "like that time when...." or "I can see that picture of..." as they struggled to remember, I knew I had done well. (And I would always wait a moment, because they would usually get it.)
Baby cards need immediate love
Unfortunately, if the card wasn't introduced quickly enough—within a day or two of the lesson—the entire memory often vanished and had to be recreated, killing the momentum of our review. This happened far too often—not because I didn't write the card soon enough (I stayed really on top of that), but because it didn't always come up for study soon enough. There were a few reasons for this:
- We often had too many due cards to get through in one session, and by default Anki puts new cards behind due ones.
- By default, Anki only introduces 20 new cards in one session (I soon uncapped this).
- Some cards were in categories that I gave lower priority to.
Two obvious cures for this problem:
- Make fewer cards. (I did get more selective as the year went on.)
- Have all cards prepped ahead of time and introduce new ones at the end of the class period they go with. (For practical reasons, not the least of which was the fact that I didn't always know what cards I was making until after the lesson, I did not do this. I might able to next year.)
Days off suck
SRS is meant to be used every day. When you take weekends off, you get a backlog of due cards. Not only do my students take every weekend and major holiday off (slackers), they have a few 1-2 week vacations built into the calendar. Coming back from a week's vacation means a 9-day backlog (due to the weekends bookending it). There's no good workaround for students that won't study on their own. The best I could do was run longer or multiple Anki sessions on return days to try catch up with the backlog. It wasn't enough. The "caught up" condition was not normal for most classes at most points during the year, but rather something to aspire to and occasionally applaud ourselves for reaching. Some cards spent weeks or months on the bottom of the stack. Memories died. Baby cards emerged stillborn. Learning was lost.
Needless to say, the last weeks of the school year also had a certain silliness to them. When the class will never see the card again, it doesn't matter whether I push the button that says 11 days or the one that says 8 months. (So I reduced polling and accelerated our cards/minute rate.)
Never before SRS did I fully appreciate the loss of learning that must happen every summer break.
Triage
I kept each course's master deck divided into a few large subdecks. This was initially for organizational reasons, but I eventually started using it as a prioritizing tool. This happened after a curse-worthy discovery: if you tell Anki to review a deck made from subdecks, due cards from subdecks higher up in the stack are shown before cards from decks listed below, no matter how overdue they might be. From that point, on days when we were backlogged (most days) I would specifically review the concept/terminology subdeck for the current semester before any other subdecks, as these were my highest priority.
On a couple of occasions, I also used Anki's study deck tools to create temporary decks of especially high-priority cards.
Seizing those moments
Veteran teachers start acquiring a sense of when it might be a good time to go off book and teach something that isn't in the unit, and maybe not even in the curriculum. Maybe it's teaching exactly the right word to describe a vivid situation you're reading about, or maybe it's advice on what to do in a certain type of emergency that nearly happened. As the year progressed, I found myself humoring my instincts more often because of a new confidence that I can turn an impressionable moment into a strong memory and lock it down with a new Anki card. I don't even care if it will ever be on a test. This insight has me questioning a great deal of what I thought knew about organizing a curriculum. And I like it.
A lifeline for low performers
An accidental discovery came from having written some cards that were, it was immediately obvious to me, much too easy. I was embarrassed to even be reading them out loud. Then I saw which hands were coming up.
In any class you'll get some small number of extremely low performers who never seem to be doing anything that we're doing, and, when confronted, deny that they have any ability whatsoever. Some of the hands I was seeing were attached to these students. And you better believe I called on them.
It turns out that easy cards are really important because they can give wins to students who desperately need them. Knowing a 6th grade level card in a 10th grade class is no great achievement, of course, but the action takes what had been negative morale and nudges it upward. And it can trend. I can build on it. A few of these students started making Anki the thing they did in class, even if they ignored everything else. I can confidently name one student I'm sure passed my class only because of Anki. Don't get me wrong—he just barely passed. Most cards remained over his head. Anki was no miracle cure here, but it gave him and I something to work with that we didn't have when he failed my class the year before.
A springboard for high achievers
It's not even fair. The lowest students got something important out of Anki, but the highest achievers drank it up and used it for rocket fuel. When people ask who's widening the achievement gap, I guess I get to raise my hand now.
I refuse to feel bad for this. Smart kids are badly underserved in American public schools thanks to policies that encourage staff to focus on that slice of students near (but not at) the bottom—the ones who might just barely be able to pass the state test, given enough attention.
Where my bright students might have been used to high Bs and low As on tests, they were now breaking my scales. You could see it in the multiple choice, but it was most obvious in their writing: they were skillfully working in terminology at an unprecedented rate, and making way more attempts to use new vocabulary—attempts that were, for the most part, successful.
Given the seemingly objective nature of Anki it might seem counterintuitive that the benefits would be more obvious in writing than in multiple choice, but it actually makes sense when I consider that even without SRS these students probably would have known the terms and the vocab well enough to get multiple choice questions right, but might have lacked the confidence to use them on their own initiative. Anki gave them that extra confidence.
A wash for the apathetic middle?
I'm confident that about a third of my students got very little out of our Anki review. They were either really good at faking involvement while they zoned out, or didn't even try to pretend and just took the hit to their participation grade day after day, no matter what I did or who I contacted.
These weren't even necessarily failing students—just the apathetic middle that's smart enough to remember some fraction of what they hear and regurgitate some fraction of that at the appropriate times. Review of any kind holds no interest for them. It's a rerun. They don't really know the material, but they tell themselves that they do, and they don't care if they're wrong.
On the one hand, these students are no worse off with Anki than they would have been with with the activities it replaced, and nobody cries when average kids get average grades. On the other hand, I'm not ok with this... but so far I don't like any of my ideas for what to do about it.
Putting up numbers: a case study
For unplanned reasons, I taught a unit at the start of a quarter that I didn't formally test them on until the end of said quarter. Historically, this would have been a disaster. In this case, it worked out well. For five weeks, Anki was the only ongoing exposure they were getting to that unit, but it proved to be enough. Because I had given the same test as a pre-test early in the unit, I have some numbers to back it up. The test was all multiple choice, with two sections: the first was on general terminology and concepts related to the unit. The second was a much harder reading comprehension section.
As expected, scores did not go up much on the reading comprehension section. Overall reading levels are very difficult to boost in the short term and I would not expect any one unit or quarter to make a significant difference. The average score there rose by 4 percentage points, from 48 to 52%.
Scores in the terminology and concept section were more encouraging. For material we had not covered until after the pre-test, the average score rose by 22 percentage points, from 53 to 75%. No surprise there either, though; it's hard to say how much credit we should give to SRS for that.
But there were also a number of questions about material we had already covered before the pretest. Being the earliest material, I might have expected some degradation in performance on the second test. Instead, the already strong average score in that section rose by an additional 3 percentage points, from 82 to 85%. (These numbers are less reliable because of the smaller number of questions, but they tell me Anki at least "locked in" the older knowledge, and may have strengthened it.)
Some other time, I might try reserving a section of content that I teach before the pre-test but don't make any Anki cards for. This would give me a way to compare Anki to an alternative review exercise.
What about formal standardized tests?
I don't know yet. The scores aren't back. I'll probably be shown some "value added" analysis numbers at some point that tell me whether my students beat expectations, but I don't know how much that will tell me. My students were consistently beating expectations before Anki, and the state gave an entirely different test this year because of legislative changes. I'll go back and revise this paragraph if I learn anything useful.
Those discussions...
If I'm trying to acquire a new skill, one of the first things I try to do is listen to skilled practitioners of that skill talk about it to each other. What are the terms-of-art? How do they use them? What does this tell me about how they see their craft? Their shorthand is a treasure trove of crystallized concepts; once I can use it the same way they do, I find I'm working at a level of abstraction much closer to theirs.
Similarly, I was hoping Anki could help make my students more fluent in the subject-specific lexicon that helps you score well in analytical essays. After introducing a new term and making the Anki card for it, I made extra efforts to use it conversationally. I used to shy away from that because so many students would have forgotten it immediately and tuned me out for not making any sense. Not this year. Once we'd seen the card, I used the term freely, with only the occasional reminder of what it meant. I started using multiple terms in the same sentence. I started talking about writing and analysis the way my fellow experts do, and so invited them into that world.
Even though I was already seeing written evidence that some of my high performers had assimilated the lexicon, the high quality discussions of these same students caught me off guard. You see, I usually dread whole-class discussions with non-honors classes because good comments are so rare that I end up dejectedly spouting all the insights I had hoped they could find. But by the end of the year, my students had stepped up.
I think what happened here was, as with the writing, as much a boost in confidence as a boost in fluency. Whatever it was, they got into some good discussions where they used the terminology and built on it to say smarter stuff.
Don't get me wrong. Most of my students never got to that point. But on average even small groups without smart kids had a noticeably higher level of discourse than I am used to hearing when I break up the class for smaller discussions.
Limitations
SRS is inherently weak when it comes to the abstract and complex. No card I've devised enables a student to develop a distinctive authorial voice, or write essay openings that reveal just enough to make the reader curious. Yes, you can make cards about strategies for this sort of thing, but these were consistently my worst cards—the overly difficult "leeches" that I eventually suspended from my decks.
A less obvious limitation of SRS is that students with a very strong grasp of a concept often fail to apply that knowledge in more authentic situations. For instance, they may know perfectly well the difference between "there", "their", and "they're", but never pause to think carefully about whether they're using the right one in a sentence. I am very open to suggestions about how I might train my students' autonomous "System 1" brains to have "interrupts" for that sort of thing... or even just a reflex to go back and check after finishing a draft.
Moving forward
I absolutely intend to continue using SRS in the classroom. Here's what I intend to do differently this coming school year:
- Reduce the number of cards by about 20%, to maybe 850-950 for the year in a given course, mostly by reducing the number of variations on some overexposed concepts.
- Be more willing to add extra Anki study sessions to stay better caught-up with the deck, even if this means my lesson content doesn't line up with class periods as neatly.
- Be more willing to press the red button on cards we need to re-learn. I think I was too hesitant here because we were rarely caught up as it was.
- Rework underperforming cards to be simpler and more fun.
- Use more simple cloze deletion cards. I only had a few of these, but they worked better than I expected for structured idea sets like, "characteristics of a tragic hero".
- Take a less linear and more opportunistic approach to introducing terms and concepts.
- Allow for more impromptu discussions where we bring up older concepts in relevant situations and build on them.
- Shape more of my lessons around the "vivid memory, card ready" philosophy.
- Continue to reduce needless student note-taking.
- Keep a close eye on 10th grade students who had me for 9th grade last year. I wonder how much they retained over the summer, and I can't wait to see what a second year of SRS will do for them.
Suggestions and comments very welcome!
Selecting vs. grooming
Content warning: meta-political, with hopefully low mind-killer factor.
Epistemic status: proposal for brain-storming.
- Representative democracies select political leaders. Monarchies and aristocracies groom political leaders for the job from childhood. (Also, to a certain extent they breed them for the job.)
- Capitalistic competition selects economic elites. Heritable landowning aristocracies groom economic elites from childhood. (Again, they also breed them.)
- A capitalist employer selects an accountant from a pool of 100 applicants. A feudal lord would groom a serf boy who has a knack for horses into the job of the adult stable man.
It seems a lot like selecting is better than grooming. After it is the modern way and hardly anyone would argue capitalism doesn't have a higher economic output than feudalism and so on.
But... since it was such a hugely important difference through history, perhaps, it was one of the things that really defined the modern world because it determines the whole social structure of societies past and present, that I think it should deserve some investigation. There may be something more interesting lurking here than just saying selection/testing won over grooming, period.
1) Can aspects of grooming as opposed to selecting/testing be steelmanned, are there corner cases when it could be better?
2) A pre-modern, medievalish society that nevertheless used a lot of selection/testing was China - I am thinking about the famous mandarin exams. Does this seem to have had any positive effect on China compared to other similar societies? I.e. is this even like that it is a big factor in the general outcomes of 2015 West vs. 1515 West? Comparing old China with similar medievalish but not selectionist (but inheritance based) societies would be useful for isolating this factor, right?
3) Why exactly does selecting and testing work better than grooming (and breeding) ?
4) Is it possible it works better because people do the breeding (intelligent people tend to marry intelligent people etc.) and grooming (a child of doctors will have an entirely different upbringing than a child of manual laborers) on their own, thus the social system does not have to do it, it is enough / better for the social system to do the selection, to do the testing of the success of the at-home grooming?
5) Any other interesting insight or reference?
Note: this is NOT about meritocracy vs. aristocracy. It is about two different kinds of meritocracy - where you either select, test people for merit (through market competition or elections) but you don't care much how to _build_ people who will have merit vs. an aristocratic meritocracy where you largely focus on breeding and grooming people into the kinds who will have merit, and don't focus on selecting and testing so much.
Note 2: is this even possible this is a false dichotomy? One could argue that Western society is chock full of features for breeding and grooming people, there are dating sites for specific groups of people, there are tons of helping resources parents can draw on, kids spend 15-20 years at school and so on, so the breeding and grooming is done all right, I am just being misled here by mere names. Such as the name democracy: it is a selection process, but who wins depends on breeding and grooming. Such as market competition: those best bred and groomed have the highest chance. Is it simply so that selection is more noticable than grooming, it gets more limelight, but we actually do both? If yes, why does selection get more limelight than grooming? Why do we talk about elections more than about how to groom a child into being a politician, or why do we talk about market competition more than how to groom a child into the entrepreneur who aces competition? If modern society uses both, why is selection in the public spotlight while grooming just being something happening at home and school and not so noticeable? (To be fair, on LW, we talk more about how to test hypotheses than how to formulate them. Is this potentially related? People are just more interested in testing than building, be that hypotheses or people?)
A Challenge: Maps We Take For Granted
Imagine that you were instantly transported into (roughly) the 13th century. I'm not great at history, but I'm picturing sometime around the crusades. You're sitting there, reading this post on your computer, and BAM! Some guy in chain mail is asking you if thou art the spawn of a demon.
Given this situation, I present to you a challenge:
You are stranded in the past. You have no modern technology except your everyday clothes. The only thing you do have is your knowledge from the future.
What do you do?
I'll make this a little more structured for the sake of clarity.
1) You appear in Great Britain (or the appropriate analogue for your native culture).
2) Assume the language barrier is surmountable - in other words, it may not be easy, but you can communicate effectively (by learning the language, or simply adapting to an older version of your native tongue).
3) Further assume that you manage to gain the ear of a ruling lord (how is not important, just say you're a wizard or something) and that he provides you with enough money, labor, and expertise (carpenters, smiths, etc.) to build something *so long as you can describe it in enough detail*.
4) You are only allowed to pull from general, scientifically literate knowledge - high school/bachelor's level only.
5) You can't use your knowledge of future events to your advantage, as it requires too expert a grasp of history. Only your knowledge of the way the world actually works is available.
The reason for 4) has to do with the point of the question. I'm trying to figure out the kind of maps that we have today that are considered "general knowledge" - the kinds of things that are so obvious to us we tend to not realize that people in the past didn't know them.
I'll go first.
The germ theory of disease didn't achieve widespread acceptance until the 19th century. In other words, I'm the only person in the past who is quite confident about how diseases are spread. This means that I can offer practical advice about sanitation when dealing with injuries and plagues. I can make sure that people wash their hands before cutting other people up, and after dealing with corpses. I can make sure that cutting instruments are sanitized (they did have alcohol) before use. And so on. This should reduce the number of deaths from disease in the kingdom, and prove my worth to the king.
I'm trying to build a list of things like this - maps of the way the world really is that we take for granted.
Have fun!
On saving the world
This is the final post in my productivity sequence.
The first post described what I achieved. The next three posts describe how. This post describes why, explaining the sources of my passion and the circumstances that convinced a young Nate to try and save the world. Within, you will find no suggestions, no techniques to emulate, no new ideas to ponder. This is a rationalist coming-of-age story. With luck, you may find it inspiring. Regardless, I hope you can learn from my mistakes.
Never fear, I'll be back to business soon — there's lots of studying to do. But before then, there's a story to tell, a memorial to what I left behind.
I was raised Catholic. On my eighth birthday, having received my first communion about a year prior, I casually asked my priest how to reaffirm my faith and do something for the Lord. The memory is fuzzy, but I think I donated a chunk of allowance money and made a public confession at the following mass.
A bunch of the grownups made a big deal out of it, as grownups are like to do. "Faith of a child", and all that. This confused me, especially when I realized that what I had done was rare. I wasn't trying to get pats on the head, I was appealing to the Lord of the Heavens and the Earth. Were we all on the same page, here? This was the creator. He was infinitely virtuous, and he had told us what to do.
And yet, everyone was content to recite hymns once a week and donate for the reconstruction of the church. What about the rest of the world, the sick, the dying? Where were the proselytizers, the missionary opportunities? Why was everyone just sitting around?
On that day, I became acquainted with civilizational inadequacy. I realized you could hand a room full of people the literal word of God, and they'd still struggle to pay attention for an hour every weekend.
This didn't shake my faith, mind you. It didn't even occur to me that the grownups might not actually believe their tales. No, what I learned that day was that there are a lot of people who hold beliefs they aren't willing to act upon.
Eventually, my faith faded. The distrust remained.
Even better cryonics – because who needs nanites anyway?
Abstract: in this post I propose a protocol for cryonic preservation (with the central idea of using high pressure to prevent water from expanding rather than highly toxic cryoprotectants), which I think has a chance of being non-destructive enough for us to be able to preserve and then resuscitate an organism with modern technologies. In addition, I propose a simplified experimental protocol for a shrimp (or other small model organism (building a large pressure chamber is hard) capable of surviving in very deep and cold waters; shrimp is a nice trade-off between the depth of habitat and the ease of obtaining them on market), which is simple enough to be doable in a small lab or well-equipped garage setting.
Are there obvious problems with this, and how can they be addressed?
Is there a chance to pitch this experiment to a proper academic institution, or garage it is?
Originally posted here.
I do think that the odds of ever developing advanced nanomachines and/or brain scanning on molecular level plus algorithms for reversing information distortion - everything you need to undo the damage from conventional cryonic preservation and even to some extent that of brain death, according to its modern definition, if wasn't too late when the brain was preserved - for currently existing cryonics to be a bet worth taking. This is dead serious, and it's an actionable item.
Less of an action item: what if the future generations actually build quantum Bayesian superintelligence, close enough in its capabilities to Solomonoff induction, at which point even a mummified brain or the one preserved in formalin would be enough evidence to restore its original state? Or what if they invent read-only time travel, and make backups of everyone's mind right before they died (at which point it becomes indistinguishable from the belief in afterlife existing right now)? Even without time travel, they can just use a Universe-sized supercomputer to simulate every singe human physically possible, and naturally of of them is gonna be you. But aside from the obvious identity issues (and screw the timeless identity), that relies on unknown unknowns with uncomputable probabilities, and I'd like to have as few leaps of faith and quantum suicides in my life as possible.
So although vitrification right after diagnosed brain death relies on far smaller assumptions, and if totally worth doing - let me reiterate that: go sign up for cryonics - it'd be much better if we had preservation protocols so non-destructive that we could actually freeze a living human, and then bring them back alive. If nothing else, that would hugely increase the public outreach, grant the patient (rather than cadaver) status to the preserved, along with the human rights, get it recognized as a medical procedure covered by insurance or single payer, allow doctors to initiate the preservation of a dying patient before the brain death (again: I think everything short of information-theoretic death should potentially be reversible, but why take chances?), allow suffering patient opt for preservation rather than euthanasia (actually, I think it should be done right now: why on earth would anyone allow a person to do something that's guaranteed to kill them, but not allowed to do something that maybe will kill, or maybe will give the cure?), or even allow patients suffering from degrading brain conditions (e.g. Alzheimer's) to opt for preservation before their memory and personality are permanently destroyed.
Let's fix cryonics! First of all, why can't we do it on living organisms? Because of heparin poisoning - every cryoprotectant efficient enough to prevent the formation of ice crystals is a strong enough poison to kill the organism (leave alone that we can't even saturate the whole body with it - current technologies only allow to do it for the brain alone). But without cryoprotectants the water will expand upon freezing, and break the cells. But there's another way to prevent this. Under pressure above 350 MPa water slightly shrinks upon freezing rather than expanding:
So that's basically that: the key idea is to freeze (and keep) everything under pressure. Now, there are some tricks to that too.
It's not easy to put basically any animal, especially a mammal, under 350 MPa (which is 3.5x higher than in Mariana Trench). At this point even Trimix becomes toxic. Basically the only remaining solution is total liquid ventilation, which has one problem: it has never been applied successfully to a human. There's one fix to that I see: as far as I can tell, no one has ever attempted to do perform it under high pressure, and the attempts were basically failing because of the insufficient solubility of oxygen and carbon dioxide in perfluorocarbons. Well then, let's increase the pressure! Namely, go to 3 MPa on Trimix, which is doable, and only then switch to TLV, whose efficiency is improved by the higher gas solubility under high pressure. But there's another solution too. If you just connect a cardiopulmonary bypass (10 hours should be enough for the whole procedure), you don't need the surrounding liquid to even be breathable - it can just be saline. CPB also solves the problem of surviving the period after the cardiac arrest (which will occur at around 30 centigrade) but before the freezing happens - you can just keep the blood circulating and delivering oxygen.
Speaking of hypoxia, even with the CPB it's still a problem. You positively don't want the blood to circulate when freezing starts, lest it act like an abrasive water cutter. It's not that much of a problem under near-freezing temperatures, but still. Fortunately, this effect can be mitigated by administering insulin first (yay, it's the first proper academic citation in this post! Also yay, I thought about this before I even discovered that it's actually true). This makes sense: if oxygen is primarily used to metabolize glucose, less glucose means less oxygen consumed, and less damage done by hypoxia. Then there's another thing: on the phase diagram you can see that before going into the area of high temperature ice at 632 MPa, freezing temperature actually dips down to roughly -30 centigrade at 209~350 MPa. That would allow to really shut down metabolism for good when water is still liquid, and blood can be pumped by the CPB. From this point we have two ways. First, we can do the normal thing, and start freezing very slowly, so minimize the formation of ice crystals (even though they're smaller than the original water volume, they may still be sharp). Second, we can increase the pressure. That would lead to near-instantaneous freezing everywhere, thus completely eliminating the problem of hypoxia - before the freezing, blood still circulated, and freezing is very quick - way faster than can ever be achieved even by throwing a body into liquid helium under normal pressure. Video evidence suggests that quick freezing of water leads to the formation of a huge number of crystals, which is bad, but I don't know near-instantaneous freezing from supercooled state and near-instantaneous freezing upon raising the pressure will lead to the same effect. More experiments are needed, preferably not on humans.
So here is my preservation protocol:
- Anesthetize a probably terminally ill, but still conscious person.
- Connect them to a cardiopulmonary bypass.
- Replacing their blood with perfluorohexane is not necessary, since we seem to be already doing a decent job at having medium-term (several days) cardiopulmonary bypasses, but that could still help.
- Submerge them in perfluorohexane, making sure that no air bubbles are left.
- Slowly raise the ambient pressure to 350 MPa (~3.5kBar) without stopping the bypass.
- Apply a huge dose of insulin to reduce all their metabolic processes.
- Slowly cool them to -30 centigrade (at which point, given such pressure, water is still liquid), while increasing the dose of insulin, and raising the oxygen supply to the barely subtoxic level.
- Slowly raise the pressure to 1 GPa (~10kBar), at which point the water solidifies, but does so with shrinking rather than expanding. Don't cutoff the blood circulation until the moment when ice crystals starts forming in the blood/perfluorohexane flow.
- Slowly lower the temperature to -173 centigrade or lower, as you wish.
And then back:
- Raise the temperature to -20 centigrade.
- Slowly lower the pressure to 350 MPa, at which point ice melts.
- Start artificial blood circulation with a barely subtoxic oxygen level.
- Slowly raise the temperature to +4 centigrade.
- Slowly lower the pressure to 1 Bar.
- Drain the ambient perfluorohexane and replace it with pure oxygen. Attach and start a medical ventilator.
- Slowly raise the temperature to +32 centigrade.
- Apply a huge dose of epinephrine and sugar, while transfusing the actual blood (preferably autotransfusion), to restart the heart.
- Rejoice.
I claim that this protocol allows you freeze a living human to an arbitrarily low temperature, and then bring them back alive without brain damage, thus being the first true victory over death.
But let's start with something easy and small, like a shrimp. They already live in water, so there's no need to figure out the protocol for putting them into liquid. And they're already adapted to live under high pressure (no swim bladders or other cavities). And they're already adapted to live in cold water, so they should be expected to survive further cooling.
Small ones can be about 1 inch big, so let's be safe and use a 5cm-wide cylinder. To form ice III we need about 350MPa, which gives us 350e6 * 3.14 * 0.025^2 / 9.8 = 70 tons or roughly 690kN of force. Applying it directly or with a lever is unreasonable, since 70 tons of bending force is a lot even for steel, given the 5cm target. Block and tackle system is probably a good solution - actually, two of them, on each side of a beam used for compression, so we have 345 kN per system. And it looks like you can buy 40~50 ton manual hoists from alibaba, though I have no idea about their quality.
I'm not sure to which extent Pascal's law applies to solids, but if it does, the whole setup can be vastly optimized by creating a bottle neck for the pistol. One problem is that we can no longer assume that water in completely incompressible - it had to be compressed to about 87% its original volume - but aside from that, 350MPa per a millimeter thick rod is just 28kg. To compress a 0.05m by 0.1m cylinder to 87% its original volume we need to pump extra 1e-4 m^3 of water there, which amounts to 148 meters of movement, which isn't terribly good. 1cm thick rod, on the other hand, would require almost 3 tons of force, but will move only 1.5 meters. Or the problem of applying the constant pressure can be solved by enclosing the water in a plastic bag, and filling the rest of chamber with a liquid with a lower freezing point, but the same density. Thus, it is guaranteed that all the time it takes the water to freeze, it is under uniform external pressure, and then it just had nowhere to go.
Alternatively, one can just buy a 90'000 psi pump and 100'000 psi tubes and vessels, but let's face it: it they don't even list the price on their website, you probably don't even wanna know it. And since no institutions that can afford this thing seem to be interested in cryonics research, we'll have to stick to makeshift solutions (until at least the shrimp thing works, which would probably give in a publication in Nature, and enough academic recognition for proper research to start).
Leaving a line of retreat for theists
Eliezer recommends that we leave a line of retreat when discussing controversial topics, since this prevents scary propositions from clouding our judgment. However, I've noticed recently that there are some topics that are just too scary for people to think about, the existence of God being a primary example. Simply put, people don't want to admit that the universe is beyond the reach of a caring God, no matter how much evidence there is to the contrary. People especially don't want to hear that they will one day cease to exist, never to be reincarnated or continued in an afterlife. I've found this to be a major stumbling block when having discussions with theists or agnostics--though the people I've talked to are willing to accept that nonbelievers can lead very moral lives, the thought that "it's just us" is the stopsign that prevents the discussion from moving further. Naturally I've explained that it's important to only believe things that are true, but for some people this meme just can't overcome the scariness of a naturalistic universe.
Have any LessWrongians managed to overcome this obstacle? If so, how? We can generalize this problem somewhat: are there effective techniques for getting people to clearly evaluate the probability of scary or depressing propositions? Explanations with the smallest amount of inferential distance are preferred--while something like cryonics does answer most of the theistic objections raised above, it's a huge distance away from most people's belief systems. (That said, it's quite possible that the answer to my question might be "No, there are no effective techniques that have short inferential distances," and in the spirit of this post I'm willing to accept that.) I'd also be interested in hearing anecdotes about similar situations if anyone has any.
How urgent is it to intuitively understand Bayesianism?
The current state of my understanding (briefly):
- I very much understand reductionism and the distinction between the map and the territory. And I very much understand that probability is in the mind.
- From what I understand, prior probability is just the probability you thought something was going to happen before having observed some evidence, and posterior probability is just the probability you think something will happen after having observed that evidence.
- I don't really have a precise way of using evidence to update my beliefs though. I'm trying to think of and explain how I currently use evidence to update my beliefs, and I'm disappointed to say that I am struggling. I guess I just sort of think something along the lines of "I'd be unlikely that I observe X if A were really true. I observed X. I think it's less likely that A is true now."
- I've made attempts at learning Bayes' Theorm and stuff. When I think it through slowly, it makes sense. But it really takes me time to think it through. Without referring to explanations and thinking it through, I forget it. And I know that that demonstrates my lack of "true" understanding. In general, my short term memory and ability to reason through quantitative things quickly seems to be well above average, but far from elite. Probably way below average amongst this community.
- What are the practical benefits of having an intuitive understanding of Bayes' Theorem? If it helps, please name an example of how it impacted your day today.
- I mention in 3) that it takes me time to think it through. To those of you who consider yourselves to have an intuitive understanding, do you have to think it through, or do you instinctively update in a Bayesian way?
- How urgent is it to intuitively understand Bayesian thinking? To use me as an example, my short-mid-term goals include getting good at programming and starting a startup. I have a ways to go, and am working towards these things. So I spend most of my time learning programming right now. Is it worth me taking a few weeks/months to study probability?
Future of Life Institute existential risk news site
I'm excited to announce that the Future of Life Institute has just launched an existential risk news site!
The site will have regular articles on topics related to existential risk, written by journalists, and a community blog written by existential risk researchers from around the world as well as FLI volunteers. Enjoy!
Are Cognitive Load and Willpower drawn from the same pool?
I was recently reading a blog here, that referenced a paper done in 1999 by Baba Shiv and Alex Fedorikhin (Heart and Mind in Conflict: The Interplay of Affect and Cognition in Consumer Decision Making). In it, volunteers are asked to memorise short or long numbers and then asked to chose a snack as a reward. The snack is either fruit or cake. The actual paper seems to go into a lot of details that are irrelevent to the blog post, but doesn't actually seem to contradict anything the blog post says. The result seems to be that those with a higher cognitive load were far more likely to chose the cake than those who weren't.
I was wondering if anyone has read any further on this line of research? The actual experiment seems to imply that the connection between cognitive load and willpower may be an acute effect - possibly not lasting very long. The choice of snack is made seconds after memorising a number and while actively trying to keep the number in memory for short term recall a few minutes later. There doesn't seem to be anything about the effect on willpower minutes or hours later.
Does anyone know if the effect lasts longer than a few seconds? If so, I would be interested in whether this affect has been incorporated into any dieting strategies.
My Skepticism
Standard methods of inferring knowledge about the world are based off premises that I don’t know the justifications for. Any justification (or a link to an article or book with one) for why these premises are true or should be assumed to be true would be appreciated.
Here are the premises:
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“One has knowledge of one’s own percepts.” Percepts are often given epistemic privileges, meaning that they need no justification to be known, but I see no justification for giving them epistemic privileges. It seems like the dark side of epistemology to me.
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“One’s reasoning is trustworthy.” If one’s reasoning is untrustworthy, then one’s evaluation of the trustworthiness of one’s reasoning can’t be trusted, so I don’t see how one could determine if one’s reasoning is correct. Why should one even consider one’s reasoning is correct to begin with? It seems like privileging the hypothesis, as there are many different ways one’s mind could work, and presumably only a very small proportion of possible minds would be remotely valid reasoners.
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“One’s memories are true.” Though one’s memories of how the world works gives a consistent explanation of why one is perceiving one’s current percepts, a perhaps simpler explanation is that the percepts one are currently experiencing are the only percepts one has ever experienced, and one’s memories are false. This hypothesis is still simple, as one only needs to have a very small number of memories, as one can only think of a small number of memories at any one time, and the memory of having other memories could be false as well.
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