PeerGynt

Karma: 246

PeerGynt 15 Jan 2011 7:48 UTC
8 points
in reply to: Daniel_Burfoot’s comment on: Simpson’s Paradox
The OP’s assertion is true. Stratifying on certain variables can introduce bias.

Consider that you have a cohort of initially healthy men, and you are trying to quantify the causal relationship between an exposure (eg eating hamburgers) and an outcome (eg death). You have also measured a third variable, which is angina pectoris (cardiovascular disease).

Assume that the true underlying causal structure, which you are unaware of, is that hamburgers cause cardiovascular disease, which subsequently causes death.

Now look at what happens if you stratify on cardiovascular disease: In the strata consisting of men who don’t have cardiovascular disease, you will find no cases of death. This will lead you to conclude that in men who don’t have cardiovascular disease, eating hamburgers does not cause death. This is false, as eating hamburgers will cause them to develop cardiovascular disease and then die.

What you have done in this situation, is stratify on a mediator, thereby “blocking” the pathway running through it. There are also many other situations in which adjusting for a variable introduces bias, but it gets more complicated from here.

For further information on this I suggest reading an upcoming book called “Causal Inference”, by James Robins and Miguel Hernan, who taught me this material. The first ten chapters are available for free online at http://www.hsph.harvard.edu/faculty/miguel-hernan/files/hernanrobins_v1.10.9.pdf .

PeerGynt 17 Jul 2013 15:27 UTC
1 point
in reply to: Liron’s comment on: How I Lost 100 Pounds Using TDT
I am not sure I am convinced by this argument, for the following reasons:

If you think of calorie content / thermodynamics as an upper bound on how much energy can be extracted from the food, you have to make an argument for what happens to the unused energy. Even if you are in a biochemical state where not all the energy is used, there is still energy floating around in your body in the form of carbohydrates, fat and protein. I can think of three possible mechanisms for what happens to this extra energy, and I am not convinced by any of them:

(1) Calories are excreted unused in their original form. However, I don’t think this happens to a meaningful extent

(2) If there is excess fat, nutrients are broken down to molecular constituents in a less efficient mechanism of cellular metabolism, ie, producing less ATP. This is a little more plausible than 1, but I think it would be evolutionary maladaptive to reduce the fuel efficiency of your engine unless it was absolutely necessary. Note that there are cases when the body does reduce the fuel efficiency (such as anaerobic metabolism), but I can’t see how this applies here

(3) (Added): If there is excess fat, the body begins to run processes that are not strictly necessary, thus using more fuel. However, I am not sure what these processes would be, or why they would be triggered by fat and not carbohydrates.

I find it plausible that increasing fat intake will help you lose weight due to regulatory pathways such as insulin, but I think this pathway operates almost exclusively through changes in appetite. I fail to see any arguments why we cannot use thermodynamics (calorie input/output) as a very good approximation of predicted weight change.

EDIT: This comment is being downvoted. I am happy to delete it if it doesn’t add to the discussion, but it would help me immensely if someone could explain why my reasoning is wrong...

EDIT2: I am not sure if I misunderstand the karma system, but I don’t think you are supposed to downvote someone for disagreeing with their conclusions. It is possible that I am wrong in my conclusions, but I don’t think this in itself is reason for downvoting.

If you disagree with my arguments, you can dissect them in the comments. Reasonable arguments with incorrect conclusions are still valuable in a discussion, and if you show why they are wrong, you will not only help me update my priors, but also help reveal a flaw in how non-trolls come to their beliefs. Hiding the comment prevents this. I don’t see any reason for downvoting, and I think the downvoters need to ask themselves if they are downvoting due to mood affiliation / cognitive bias.

PeerGynt 17 Jul 2013 18:29 UTC
0 points
in reply to: Desrtopa’s comment on: How I Lost 100 Pounds Using TDT
By which mechanism do these nutrients get excreted? Urine? Bile? Non-absorption?

My impression is that carbohydrates in urine is something that we only see to a significant extent when blood glucose concentration is at diabetic levels. Protein and fat in urine occurs, but it doesn’t seem to me that this happens to an extent where it can make a difference to the total energy picture

I don’t think excreting them through bile would work, the nutrients would just be reabsorbed further down the gastrointestinal tract.

It is possible that at very high intake levels, there is significant non-absorption of fat. Maybe this happens in competitive eaters, but I am not convinced it can explain much at fat intake levels seen in ordinary people..

PeerGynt 17 Jul 2013 18:58 UTC
0 points
in reply to: [deleted]’s comment on: How I Lost 100 Pounds Using TDT
Thank you, that was helpful.

Note that I don’t disagree with anything in that Mayo Clinic article. The point about “pounds of fat, muscle and water” is obviously true and does not contradict anything I said. The points about “metabolic rate” and “response to reduced calories” just seem to say that sometimes it is difficult to estimate the “calories out” part of the equation, and that it is endogenous to the system. This is also obviously true. I still find it difficult to believe that we can affect the metabolic rate to an extent that matters in the final analysis, based on the fat/protein/carbohydrate content of our diet..

PeerGynt 17 Jul 2013 19:11 UTC
2 points
in reply to: Manfred’s comment on: How I Lost 100 Pounds Using TDT
This article says that there is some non-absorption of fat in healthy people, and much greater non-absorption in people with cystic fibrosis.

If you want to convince me that I should consider this when I choose the fat/carbohydrate/protein content of my diet, you would have to make an argument that the percentage of fat that is not absorbed is a function of my diet, ie, causally related to what I choose to eat.

I’m not saying this is not theoretically possible, but my intuition tells me that the variation in absorbtion that is caused by diet, is unlikely to have a major impact in the final analysis

PeerGynt 17 Jul 2013 19:25 UTC
0 points
in reply to: [deleted]’s comment on: How I Lost 100 Pounds Using TDT
OK. I’ll accept your rephrasing. Let us assume that “calories out” is always difficult to estimate and depends on a lot of factors such as muscle mass and total calorie intake.

I took the original comment to mean that we can eat very large amounts of fat and protein, because our bodies would somehow react, in response to the proportion of different nutrients in our diet, and change how efficiently we use energy. I find it difficult to believe that this would explain much of change in body weight. I find it much easier to believe that it would change our appetites and thus reduce calorie intake.

I am certainly willing to update my priors if someone convinces me of a plausible mechanism by which proportion of each nutrient alters efficiency of energy use..

PeerGynt 18 Jul 2013 14:54 UTC
1 point
in reply to: Richard_Kennaway’s comment on: How I Lost 100 Pounds Using TDT
There is obviously thermodynamic energy in food which is not absorbed in the gastrointestinal tract. Fiber is an example of this. Energy which is not absorbed is not listed on the nutrition label of food. When I say ‘calories’, I mean the biochemically available energy in absorbed macronutrients such as fat, carbohydrates, protein and alcohol.

Nobody doubts that thermogenesis uses energy. This is a special case of my mechanism 3. It is part of the ‘energy used’. Again, if you want to convince me that you can eat 3000 calories of fat without gaining weight, you would have to make an argument that the proportion of fat in my diet has a causal effect on thermogenesis, ie, that my body will start running additional thermogenesis because I ate fat instead of carbohydrates.

Your claim that CICO is as helpful as MIMO is clearly ridiculous, and if you truly believe this, then supermodels eating tissue paper are more rational than you, as their beliefs will lead to more accurate predictions.

The point I am trying to make is that our body is an efficient engine due to evolutionary pressure, that energy doesn’t just disappear (if it did, we would observe large amounts of unmetabolized macronutrients in urine), and that even if CICO is not the whole picture, it explains a very large part of the variation in body weight observed in human populations

PeerGynt 18 Jul 2013 17:10 UTC
0 points
in reply to: Richard_Kennaway’s comment on: How I Lost 100 Pounds Using TDT

What is more ridiculous about MIMO than CICO? Conservation of matter, can’t argue with that.

OK, I see the point. But multicellular life evolved as thermodynamic engines, not as fusion plants. Over billions of years, cells were surviving based on how efficiently they could extract thermodynamic energy from macronutrients, to power intracellular processes. This is what we are optimized for. If we had been able to use fusion power in our evolutionary past, MIMO would be a more appropriate level at which to draw your map.

PeerGynt 24 Jul 2013 0:05 UTC
4 points
in reply to: Peter Wildeford’s comment on: Why Eat Less Meat?

I only think factory-farmed meat is the problem. I use “eat less meat” as a shorthand, since nearly all meat is factory-farmed meat.

Factory-farmed meat converts photosynthetic energy (grass) to food much more efficiently than free-range farming. Factory farming requires less inputs in terms of arable land and water, and emits less CO2. If everyone in the world ate non-factory farmed meat, we would have to cut down the Amazon many times over, thereby drastically reducing earth’s capacity to convert CO2 back to carbohydrates.

When you decide whether your meat should be factory farmed or not, , there are consequences on two scales that are negatively correlated: Animal welfare and global warming. Which of these scales you give most weight to, will depend on your prior for anthropogenic global warming, on your beliefs about the consequences of global warming, and on the priority you give animals in your aggregation scheme over individuals with moral standing.

PeerGynt 24 Jul 2013 15:37 UTC
8 points
in reply to: Peter Wildeford’s comment on: Why Eat Less Meat?
A source is “Allison, Richard. “Organic chicken production criticised for leaving a larger carbon footprint.” Poultry World. 1 Mar. 2007”. This article is behind a paywall. I am pasting a table from the article:

AVERAGE ENVIRONMENTAL IMPACT FROM POULTRY PRODUCTION (% DIFFERENCE TO CONVENTIONAL) Organic Free range

Energy use +33% +25%

Global warming potential (CO2) +46% +20%

Eutrophication potential +75% +28%

Acidification potential +52% +33%

Pesticide use (dose/ha) −92% +12%

Note: This article is in a trade publication and could be biased. It is based on an original report which I could not locate, and which apparently has sparse data. Obviously, more research is needed.

My prior beliefs are not the result of scientific studies, but follow from the following observations:

(1) To reduce global warming, we need to maximize the number of calories produced per unit of CO2 emission

(2) The most effective way we can alter that ratio, is by reducing the amount of biochemical energy that is used to power the biochemical processes of farm animals over the course of their lives. This is primarily a function of duration of their lives.

(3) Factory farming achieves shorter duration, by having the animals grow more quickly

(4) Another way we can reduce the net amount of CO2 produced per unit food, is by reducing the amount of land used, thus allowing less deforestation.

(5) Factory farming achieves this by using less land

(6) I cannot see any other mechanisms that differ between factory farming and organic farming which would have a major net effect on the carbon cycle.

Ethics in a Feedback Loop: A Parable

PeerGynt25 Jul 2014 16:25 UTC

12 points

139 comments2 min readLW link

PeerGynt 25 Jul 2014 17:09 UTC
4 points
in reply to: Lumifer’s comment on: Ethics in a Feedback Loop: A Parable
In this society, it is generally accepted that tickling is not something that requires consent.

Even more than the Martians want to tickle humans, they want to carry them away to their mothership to experiment on them. Everyone agrees that experimentation on humans requires their consent. Part of the socially accepted foreplay that sometimes leads to humans giving their consent to be experimented on, consists of the martian tickling the human behind the ear.

PeerGynt 25 Jul 2014 18:06 UTC
3 points
in reply to: Lumifer’s comment on: Ethics in a Feedback Loop: A Parable
I definitely see the humans as agents, whose preferences are morally relevant. In fact, the reason this is even ethically ambiguous in the first place, is that humans have a preference not to be tickled by green martians.

The reason humans come across as passive, is that I am specifically asking about the ethics of an action that is generally conducted by the active Martian to the passive human. It is at least theoretically possible that this question can be resolved without considering any ethical dilemmas that the humans face. This does not mean that the humans are not considered as important moral agents, only that their agency is not something that has any impact on the ethics of a choice made my Martians.

If you can think of a reason why having a full map of the ethical agency of the human is necessary to resolve the ethics of the choice faced by the Martian, I would be very interested in hearing it and will update accordingly.

PeerGynt 25 Jul 2014 19:17 UTC
2 points
in reply to: Lumifer’s comment on: Ethics in a Feedback Loop: A Parable
OK. Good point. I am going to specify that in this thought experiment, tickling is only effective if there is no explicit consent.

Edit: See definition of tickling here: http://lesswrong.com/lw/klx/ethics_in_a_feedback_loop_a_parable/b5ft?context=1#b5ft

Also, note that this is a thought experiment. The point of this comment is not to make a claim about the truth value of the statement “flirting is only effective if there is no explicit consent”, but to explore the ethical consequences of a world in which this is true.

PeerGynt 25 Jul 2014 19:22 UTC
4 points
in reply to: polymathwannabe’s comment on: Ethics in a Feedback Loop: A Parable
OK, I really would prefer that this discussion stays on the abstract level, but in order to avoid confusion, I will provide a translation of the intended metaphors:

Green Martian = Low Status Male

Blue Martian = High Status Male

Earthling = Female

Tickling = Flirting (Including obnoxious strategies such as “negs” and “kino escalation”)

The moderately painful sting of the tentacles of the Green Martian = Creepiness, Social Awkwardness, etc

Experimentation on Earthlings (defined in comments) = Sex
What links here?
- Richard_Kennaway's comment on Ethics in a Feedback Loop: A Parable by PeerGynt (25 Jul 2014 20:31 UTC; 20 points)
- NoSuchPlace's comment on Ethics in a Feedback Loop: A Parable by PeerGynt (25 Jul 2014 22:30 UTC; 0 points)

PeerGynt 25 Jul 2014 20:55 UTC
12 points
in reply to: Richard_Kennaway’s comment on: Ethics in a Feedback Loop: A Parable
Let me just point out that the post was an attempt to discuss ethics in a hypothetical world where certain PUA claims about human psychology are true. I think this is an important question, and I did not want it to degenerate into a discussion about whether the claims themselves are true.

I tried my best to make the analogy as neutral as possible, by making women the “humans”, describing the PUA strategies as having a real harmful effect on women, and generally making their dislike of PUA strategies seem entirely reasonable.

I don’t see how the post is tendentious. I don’t think the analogy has any obvious ethical solution, and I am genuinely asking people for insight into what the relevant ethics are in this hypothetical world. I don’t see how I am leading people to give me validation on my views, because I am not even sure what my views are.

PeerGynt 25 Jul 2014 21:34 UTC
8 points
in reply to: polymathwannabe’s comment on: Ethics in a Feedback Loop: A Parable
Those are not my views:

First of all, I took no position on the truth value of the premises.

Secondly, I fully recognize that my analogy is a simplified map of a map. It does not accurately represent the full territory.

The question is whether the aspects of the territory that I have glossed over are important for the resolution of the ethical question. If there are any such aspects, please feel free to point them out. I do recognize that some of the aspects that have been pointed out, such as consent, are important. I have upvoted those comments and attempted to explain why I think you can make the argument that the analogy still has some validity.

PeerGynt 25 Jul 2014 21:44 UTC
0 points
in reply to: David_Gerard’s comment on: Ethics in a Feedback Loop: A Parable
I am certainly learning from any useful comments that are made, regardless of which position they take. This is not one of those comments. It is also the only comment in the thread which I have downvoted—I am trying to have a discussion about ethics in a hypothetical world, not a flame war.

PeerGynt 25 Jul 2014 21:58 UTC
0 points
in reply to: Adele_L’s comment on: Ethics in a Feedback Loop: A Parable
Thank you, this is exactly the kind of discussion I was hoping for. I don’t really have anything to add, I agree with essentially everything here. Can we can please keep the discussion at this level?

PeerGynt 25 Jul 2014 22:10 UTC
−2 points
in reply to: buybuydandavis’s comment on: Ethics in a Feedback Loop: A Parable
I am a moral realist, I believe there exists an objective moral standard which is part of the territory. This is the moral standard we are talking about.

Obviously, we are unable to know whether our ethical maps correspond to the ethical territory. We should therefore update our priors about the ethical territory in response to good arguments and thought experiments. Throughout this discussion, I have made several updates to my beliefs.

If we don’t believe there is such a thing as an objective ethical standard, if the territory doesn’t exist, then I fail to see the point in even discussing ethics.

PeerGynt

Ethics in a Feed­back Loop: A Parable

Ethics in a Feedback Loop: A Parable