Your Evolved Intuitions

Part of the sequence: Rationality and Philosophy

We have already examined one source of our intuitions: attribute substitution heuristics. Today we examine a second source of our intuitions: biological evolution.

 

Evolutionary psychology

Evolutionary psychology1 has been covered on Less Wrong many times before, but let's review anyway.

Lions walk on four legs and hunt for food. Skunks defend themselves with a spray. Spiders make webs. Each species is shaped by selection pressures, and is different from that of other species.

Certain evolved psychological mechanisms in humans are part of what makes us like each other and not like lions, skunks, and spiders.

These mechanisms evolved to solve specific adaptive problems. It is not an accident that people around the world prefer calorie-rich foods,2 that women around the world prefer men with resources,3 that men around the world prefer women with signs of fertility,4 or that most of us inherently fear snakes and spiders but not cars and electrical outlets.5

An an example of evolutionary psychology at work, consider the 'hunter-gatherer hypothesis' that men evolved psychological mechanisms to aid in hunting, while women evolved psychological mechanisms to aid in gathering.6 This hypothesis leads to a list of bold predictions. If the hypothesis is correct, then:

  1. Men in modern tribal societies should spend a lot of time hunting, and women more time gathering.
  2. Humans should show a greater tendency toward strong male coalitions than similar species in which males do not hunt much, because strong male coalitions are required to hunt big game.
  3. Because meat from most game comes in quantities larger than a single hunter can consume, and because hunting success is highly variable (one week may be a success, but perhaps not the next week), humans should exhibit food sharing and reciprocal altruism.
  4. We should expect to see a sexual division of labor, due to the different traits conducive for hunting vs. gathering.
  5. Men should exploit status gains to be had from 'showing off' large hunting successes.
  6. Men should have superior cognitive ability to navigate across large distances and perform 3D mental rotation tasks required for throwing spears and similar hunting acts. Women should have superior cognitive ability with spacial location memory and object arrays.

And as it turns out, all these predictions are correct.7 (And no, evolutionary psychologists do not only offer 'postdictions' or 'just so' stories. Besides, probability theory does not have separate categories for 'predictions' and 'postdictions'.)

 

Kin loyalty

Consider the intuition that we have more responsibility for the well-being of our close relatives than for the well-being of distant relatives or strangers. We would expect human evolution to produce exactly such an intuition given Hamilton's rule, which states that the reproductive cost to an agent is less than the genetic relatedness of the recipient to the agent multiplied by the additional reproductive benefit gained by the recipient of the altruistic act.

That's a mouthful, so instead let me illustrate the consequences of Hamilton's rule:

Imagine that you pass by a river and notice that some of your genetic relatives are drowning in a ferocious current. You could jump in the water to save them, but you would pay with your own life. According to Hamilton's rule, selection will favor decision rules that, on average, result in your jumping into the water to save three of your brothers, but not one. You would be predicted not to sacrifice your own life for just one brother, because that would violate Hamilton's rule. Using the logic of Hamilton's rule, evolved decision rules should lead you to sacrifice your own life for five nieces or nephews, but you would have to save nine first cousins before you would sacrifice your own life.8

Hamilton's rule has indeed been observed at work in a wide variety of contexts.9

My intuition that I am more responsible for the well-being of my brother than my cousin, and more responsible for the well-being of my cousin than a stranger, looks like a good candidate for an evolved intuition.

 

Essentialism

Uneducated people around the world believe that organisms come in discrete packets, and that each species has an 'essence' that produces its form and abilities. The intuitive appeal of this essentialism often trumps the explicitly learned gradualism of biological evolution. Even someone who has read Richard Dawkins argue against essentialism might find himself the very next day stuck in essentialist thinking. Why? Many researchers have suggested that an evolved, intuitive 'folk biology' is responsible.10

These essentialist intuitions emerge early in life across all cultures we have studied.11 For example, children may believe that

...if you remove the insides of a dog, it loses its 'essence' and is no longer really a dog anymore - it can't bark or bite. But if you remove its outsides or change its external appearance so that it doesn't look like a dog, children still believe that it has retained its essential 'dogness.'12

Many researchers think that essentialist intuitions evolved because it's useful for humans to respond to organisms in this way. With essentialist thinking, we can very quickly drop organisms into categories concerning what we can and can't eat, what we can capture, what might capture us, and so on.

Essentialism has had a long-lasting hold on the minds of many philosophers, and greatly influenced their conclusions even after Darwin.

 

Heuristics and biases

Human reasoning is subject to a long list of biases. Why did we evolve such faulty thinking processes? Aren't false beliefs bad for survival and reproduction?

Many researchers suggest that while humans are poor at formal logic and Bayesian inference, humans display a kind of 'ecological rationality'.13

Over evolutionary time, the human environment has had certain statistical regularities: Rain often followed thunder, violence sometimes followed angry shouts, sex sometimes followed prolonged eye contact, dangerous bites often followed getting too close to a snake, and so on. These statistical regularities are called ecological structure. Ecological rationality consists of evolved mechanisms containing design features that utilize ecological structure to facilitate adaptive problem solving.

The shape and form of cognitive mechanisms, in other words, coordinate with the recurring statistical regularities of the ancestral environments in which humans evolved. We fear snakes and not electrical outlets...

[Moreover], theories of formal logic that are content independent... are exceptionally poor at solving real adaptive problems. The world is full of logically arbitrary relationships: Dung happens to be potentially dangerous to humans, for example, but provides a hospitable home for dung flies. So applying formal logic cannot in principle solve the adaptive problem of avoiding dung. The only thing that can solve it is a content-specific mechanism, one that has been built over evolutionary time to capitalize on the recurring statistical regularities associated with dung as it interacted with our hominid ancestors.14

 

Conclusion

Our brains may have evolved intuition-generating mechanisms that worked for solving particular adaptive problems in the ancestral environment, but we may not have evolved psychological mechanisms that generate accurate intuitions useful for doing philosophy. For example, it seems unlikely that we evolved a mechanism that gives us reliable intuitions about the metaphysical possibility or impossibility of zombies.

 

Next post: Intuition and Unconscious Learning

Previous post: How You Make Judgments

 

 

Notes

1 Recent introductions to the field include: Buss (2011); Workman & Reader (2008); Gaulin & McBurney (2003). It is also worth mentioning one of the major problems with evolutionary psychology. Evolutionary psychologists tend to focus on subjects that are difficult to test because they are uniquely human but also universally human, which is bad for testability (see here and here). For other difficulties, see Problems in Evolutionary Psychology.

2 Birch (1999); Krebs (2009).

3 Buss et al. (1990); Buss & Schmitt (1993); Khallad (2005); Gottschall et al. (2003); Gottschall et al. (2004); Kenrick et al. (1990); Gustavsson & Johnsson (2008); Wiederman (1993); Badahdah & Tiemann (2005); Marlowe (2004); Fisman et al. (2006); Asendorpf et al. (2010); Bokek-Cohen et al. (2007); Pettay et al. (2007).

4 Signs of fertility that men prefer include youth (Buss 1989a; Kenrick & Keefe 1992; Kenrick et al. 1996), clear and smooth skin (Sugiyama 2005; Singh & Bronstad 1997; Fink & Neave 2005; Fink et al. 2008; Ford & Beach 1951; Symons 1995), facial femininity (Gangestad & Scheyd 2005; Schaefer et al. 2006; Rhodes 2006), long legs (Fielding et al. 2008; Sorokowski & Pawlowski 2008; Bertamini & Bennett 2009; Swami et al. 2006), and a low waist-to-hip ratio (Singh 1993, 2000; Singh & Young 1995; Jasienska et al. 2004; Singh & Randall 2007; Connolly et al 2000; Furnham et al 1997). Even men blind from birth prefer a low waist-to-hip ratio (Karremans et al. 2010). Note that standards for beautiful faces emerge before cultural can have much effect (Langlois et al. 1990) and that standards of beauty are relatively consistent across cultures (Cunningham et al. 1995; Cross & Cross 1971; Jackson 1992; Jones 1996; Thakerar & Iwawaki 1979).

5 Buss (2011), pp. 92-94.

6 Buss (2011), p. 85.

7 Evidence cited by prediction number. 1: Hewlett (1991); Lee (1979). 2: Tooby & DeVore (1987). 3: Trivers (1971). 4: Roskraft et al. (2004); Tooby & DeVore (1987). 5: Hawkes (1991); Wiessner (2002). 6: Silverman & Philips (1998); Silverman et al. (2000); Eals & Silverman (1994); Silverman et al. (2007); New et al. (2007); Silverman & Choi (2005); Lippa et al. (2010).

8 Buss (2011), p. 238-239.

9 Buss (2011) calls Hamilton's theory of inclusive fitness (expressed in Hamilton's rule) "the single most important theoretical revision of Darwin's theory of natural selection in the past century" (p. 239). For a review of some of the evidence that supports Hamilton's rule, see Buss (2011), chapter 8.

10 Atran (1998); Berlin (1992); Keil (1995); Medin & Atran (1999).

11 Sperber & Hirschfeld (2004).

12 Buss (2011), p. 73.

13 Tooby & Cosmides (1998). Haselton et al. (2009) say humans are 'adaptively biased,' while Kenrick et al. (2009) say we are 'adaptively rational.'

14 Buss (2011), pp. 396-397.


 

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Another problem with using a list of postdictions to support evolutionary psychology is that you have not shown that it cannot also predict the opposite - as it sometimes can if you choose to tell the story differently.

Premise: Men in tribal societies spend a lot of time hunting, and women more time gathering.

  1. Human males should show a greater tendency toward isolation than in similar species in which males do not hunt much, because hunting for small and medium-sized game is a solitary endeavor.
  2. All people should claim status from large successes, because of our background in tribal politics.
  3. Women should have superior cognitive ability to use and construct more pieces of rudimentary technology and perform 3D mental rotation tasks required for weaving baskets and similar acts. Men should have superior cognitive ability with spatial location memory and perception because of its use in hunting.

In response, I just want to repeat everything Eliezer said here and here, and point you to this article.

Another problem with using a list of postdictions to support evolutionary psychology is that you have not shown that it cannot also predict the opposite - as it sometimes can if you choose to tell the story differently.

This is the most trenchant criticism in my opinion. I disagree with those who say that postdictions are worthless. But they've got to be honest postdictions. They have to be real probabilistic consequences of the logic of the theory.

I disagree with those who say that postdictions are worthless

Good. The reason is explained by Yudkowsky:

People eagerly jump the gun and seize on any available reason to reject a disliked theory. That is why I gave the example of 19th-century evolutionism, to show why one should not be too quick to reject a "non-technical" theory out of hand. By the moral customs of science, 19th-century evolutionism was guilty of more than one sin. 19th-century evolutionism made no quantitative predictions. It was not readily subject to falsification. It was largely an explanation of what had already been seen. It lacked an underlying mechanism, as no one then knew about DNA. It even contradicted the 19th-century laws of physics. Yet natural selection was such an amazingly good post-facto explanation that people flocked to it, and they turned out to be right. Science, as a human endeavor, requires advance prediction. Probability theory, as math, does not distinguish between post-facto and advance prediction, because probability theory assumes that probability distributions are fixed properties of a hypothesis.

The rule about advance prediction is a rule of the social process of science - a moral custom and not a theorem. The moral custom exists to prevent human beings from making human mistakes that are hard to even describe in the language of probability theory, like tinkering after the fact with what you claim your hypothesis predicts. People concluded that 19th-century evolutionism was an excellent explanation, even if it was post-facto. That reasoning was correct as probability theory, which is why it worked despite all scientific sins. Probability theory is math. The social process of science is a set of legal conventions to keep people from cheating on the math.

and:

But the rule of advance prediction is a morality of science, not a law of probability theory. If you have already seen the data you must explain, then Science may darn you to heck, but your predicament doesn't collapse the laws of probability theory. What does happen is that it becomes much more difficult for a hapless human to obey the laws of probability theory. When you're deciding how to rate a hypothesis according to the Bayesian scoring rule, you need to figure out how much probability mass that hypothesis assigns to the observed outcome. If we must make our predictions in advance, then it's easier to notice when someone is trying to claim every possible outcome as an advance prediction, using too much probability mass, being deliberately vague to avoid falsification, and so on.

Probability theory has no separate category for 'prediction' and 'postdiction'.

But yes, you need to be making predictions and postdictions that actually follow from the math of your theory. Though, semitechnical theories can still build up a high enough score to beat out rival theories.

For those people who claim that evolutionary psychology isn't predictive:

These data show that children living with one genetic parent and one stepparent are roughly forty times more likely to be physically abused than children living with both parents.This greater risk rate occurs even when other factors such as poverty and socioeconomic status are controlled. Daly and Wilson concluded that "step-parenthood per se remains the single most powerful risk factor for child abuse that has yet been identified".... Some people, of course, might claim that such findings are "obvious" or that "anyone could have predicted them." Perhaps so. But the fact remains that hundreds of previous studies of child abuse failed to identify step-parents as a risk factor for child abuse until Daly and Wilson approached the problem with an evolutionary lens.

Buss (2008). Evolutionary Psychology: The New Science of Mind (3rd ed.). Prentice Hall. 7. 211-12

And of course, there are many similar examples throughout the book. I literally just opened it to a random page, and found that example.

At some point, the refrain of "Non-predictive! Just-so story! It's a pseudoscience!" starts to look like motivated cognition.

hundreds of previous studies of child abuse failed to identify step-parents as a risk factor for child abuse

Here's a case of confusion. Isn't this conjecture obvious? Cinderella? Beaten like a red headed stepchild?

I'll take it as more likely that an evo psych researcher pointed out the obvious, than an evo psych researcher pointed out the obvious because of his evo psych theory.

I'll take it as more likely that an evo psych researcher pointed out the obvious, than an evo psych researcher pointed out the obvious because of his evo psych theory.

One would hope so!

But I reject (what seems to be) the intended connotation - that having an evo psych theory would not have a dramatic influence on the probability that a prominent researcher would point out this particular instance of the obvious.

It may be useful to focus on the 'pointed out' part. Even allowing that a fact is 'obvious' enough that it occurs to everyone, when it comes to pointing things out - particularly in the form of presenting it in a formal research context - incentive matters.

Most people who have proven their ability to gain academic credibility are wise enough to not go around making controversial claims unless they have a personal stake in it. Their intellectual territory must somehow be expanded by the pronouncement. An evo psych researcher potentially gains status by showing a new area where his theory can claim authority.

A non-evo psych researcher is less likely to gain from spouting step-parent risk factors. He or she may even benefit from rejecting the step-parent influence in order to support an entirely situational based model of social behaviour. Whatever it takes to make the situation look more like the kind of 'nail' that their clique's 'hammer' is built to handle.

I rather agree with you fully, but you are elaborating 'because of his evo psych theory' differently than I intended. The OP's point appears to be that no one [or at least expert] was aware of the connection, until evo psych created a framework that generated a prediction along those lines, that then allowed people to begin focusing on that connection. That's the sense I used.

Your political story, along the lines of gravestone to gravestone, I find reasonable and likely.

Some lazy googling indicates the phrase "beaten like a red-headed stepchild" was raised to contemporary popular consciousness in 1986's "The wrath", years after Daly and Wilson. Originally it was racist, specifically referring to the way one might treat the result of a wife's earlier dalliances with Irish immigrants.

I'm not sure I trust my intuitions about what an average high school dropout could tell me in the 1970's. But I consider it significant that professionals looked into this question, and did not notice that factor previously, an unlikely result if it was both widely known and actually present.

I suspect this may be a case of the professionals not wanting to notice because they didn't want to seem politically incorrect.

I suspect this may be a case of the professionals not wanting to notice because they didn't want to seem politically incorrect.

The time prior to the Daly and Wilson paper (1980) included a lot of time when modern notions of political correctness were not operative.

I suspect this may be a case of the professionals not wanting to notice because they didn't want to seem politically incorrect.

I think you're right. It is usually best to conform and be politically correct in most cases, biding time until there is a specific issue on which you can make a stand with an expectation of significant benefit to yourself or your objectives. Choosing a battle.

Buller claims that the statistics come from police reports and that the police had previously been trained to look for stepparents as a source of child abuse. If so, 1 this was well known by nonpsychologists and 2 the magnitude of the effect may be overstated. Is there a problem with this critique?

Is there a problem with this critique?

For 1, how is that a even critique? Is it possible for psychologists to have failed to understand something that cops understood? It doesn't even seem surprising that police, who have generations of practical experience dealing with abuse would notice the trend before ivory-tower academics.

As for 2, I don't think that suggests the effect is overstated, except maybe very weakly. The effect is so huge that it's hard to believe that police suspicion of step-parents can "explain it away".

Much of the commentary here has turned into yet another debate about just how useless and unscientific evolutionary psychology is. (Notice how I cleverly signaled my own viewpoint about the debate. :) But do we really need to have this debate?

It occurs to me that Luke's argument (about the misuse of intuitions by philosophers) really is independent of whether present-day evolutionary psychologists know what they are talking about. All Luke's arguments, if I understand them, really need is that some intuitions are innate and derived from our evolutionary history, some are learned, and that some are generated on the spot by fallible cognitive processes. It really doesn't matter whether an innate intuition arises as an evolutionary adaptation or an evolutionary accident - it still doesn't provide a philosopher what he needs to ground his arguments.

If I am right here, and the validity of evolutionary psychology is irrelevant to Luke's arguments, then lets move on. We can debate whether the validity of evolutionary psychology is irrelevant more generally at some other time.

I endorse all of this.

As for your comment below about how I "seemed to suggest [evpsych] was the best thing since slided bread," I'm not sure where you got such an idea. Evpsych is, as others have pointed out, full of holes. I pointed to some of those holes in my first footnote.

As for your comment below about how I "seemed to suggest [evpsych] was the best thing since slided bread," I'm not sure where you got such an idea.

Other people who talk about evo psych think it is the best thing since sliced bread. You talk about evo psych. Therefore, you think evo psych is the best thing since sliced bread.

It is approximately the same intuition at play as that which you describe as 'essentialism' - and nearly ubiquitous when speaking with humans. If you say something about a topic or theory you can assume that you will be judged according to whatever other people who talk about the same topic, position or theory have said.

Other people who talk about evo psych think it is the best thing since sliced bread. You talk about evo psych. Therefore, you think evo psych is the best thing since sliced bread.

It is approximately the same intuition at play as that which you describe as 'essentialism'

It's also a perfectly valid piece of Bayesian reasoning.

It's also a perfectly valid piece of Bayesian reasoning.

It isn't if it is made as a logical deduction - as it was presented in the quote and also how it is frequently implemented in practice. The valid Bayesian reasoning would be a well calibrated calculation of the probability that the speaker happens to think those same thoughts given the remembered behaviours of other individuals of the same species. If only that was how humans behaved!

If I am right here, and the validity of evolutionary psychology is irrelevant to Luke's arguments, then lets move on. We can debate whether the validity of evolutionary psychology is irrelevant more generally at some other time.

Supposing that the dispute is tangential to the topic of the article, I've seen many such disputes arise in comments without their digressiveness being raised as an objection. Is your concern that you think this threatens to overwhelm the main topic?

No, actually I'm not all that concerned. Mostly, I just wanted to point out just how low the stakes are in the often-heated arguments about evopsych. Luke wrote about evopsych, and seemed to suggest that it was the best thing since sliced bread, but it often seems that the people who praise evopsych (but don't have a particular just-so-story in mind) really aren't interested in the actual explanations that evopsych offers; instead they just are pleased to be able to stick pins into the inflated and self-congratulatory views of human nature which arise from non-evolutionary accounts of our origins.

they just are pleased to be able to stick pins into the inflated and self-congratulatory views of human nature which arise from non-evolutionary accounts of our origins.

That makes it sound as if the evopsych controversy is evolutionists versus creationists. My impression was that it's mainly naturists versus nurturists.

You may be right, but if so, that paints a pretty dismal picture of the current state of psychology and anthropology. If you want to determine whether some human trait (a propensity toward alcoholism, say) is a result of nature or nurture, inventing competing just-so stories about the origin of that trait is a pretty poor way to decide between the hypotheses. And if you already know that a trait is innate, a disputed evopsych explanation brings nothing extra to the party.

And if you already know that a trait is innate, a disputed evopsych explanation brings nothing extra to the party.

What it does do is tell you what to bring to the next party and perhaps a hint as to what to do about the hangover the next day.

Improving our model of how the traits that know about evolved allows us to form better hypothesis about what other traits may be present and worth investigating. It could also suggest avenues for research in the area of physiology. Knowing why something exists can give some clues about how to go about fixing it when it is broken.

Plus... I like to know stuff! Causes intrigue me. Raw lists of correlations are dull.

Ok, but I don't see how that is responsive to my point. Which was that you really ought to determine whether something is innate or learned before you begin generating hypotheses as to just how it became innate. That is, determine the proximate cause first, then go to work on other kinds of causation.

ETA: Btw, it is "group selection", not "group evolution".

ETA#2: Ah, if you didn't realize that the 'party' in question is the nature/nurture debate, then you would think that you were being responsive. Kindly ignore the snarkiness.

Btw, it is "group selection", not "group evolution".

I had assumed that I made a slip of the fingers but looking back I don't seem to have used that phrase at all. Was that me or someone else you were referring to?

It was you and then Matt_Simpson and then you again. But it seems to have died out now.

Ahh, I see.

in the first context it was 'group selection' that the researches intended to facilitate but not what actually occurred. The resulting outcome was instead individual selection being the dominant factor in how the groups evolved. This is to say that 'group' and 'evolution' are used correctly as independent terms, not as a phrase referring to a single construct.

The latter two should be 'group selection' so I corrected my follow up there, and the Matt quote with suitable edit-brackets to maintain the consistency in reply.

It is cheating to make predictions that are actually postdictions. To test hypotheses we have to look at questions for which we don't have information and then test those questions by gathering new information. A lot of the "evolutionary psychology" are really "Just So" stories without this kind of hypothesis testing.

A huge amount of science operates on postdictions. That's not 'cheating', it's just not as impressive as Einstein predicting gravitational lensing. Just as in other sciences, including evolutionary biology, evolutionary psychology uses multiple converging lines of evidence to weigh the probabilities of hypotheses (see, e.g., Buss, The Handbook of Evolutionary Psychology, pp. 457-465: PDF).

And in fact, evolutionary psychologists often do make novel predictions and then go out and make the observations that either confirm or disconfirm the hypothesis.

I suspect that those who say evolutionary psychology is nothing but 'just so' stories are not actually keeping up with the science but instead are operating under cached thoughts.

Ok, update my cache: you listed 7 bold postdictions; please list some bold predictions.

Its true that not all science is prospective, but you need to at least avoid looking at the data when making hypotheses you will then test against that data. Often we divide a data set to do this. Its much easier to do this with quantitative hypotheses than qualitative ones.

knb provides one example here, though I can come back add others later.

Highly relevant is this post from Yudkowsky.

If Buller is to be believed that's another postdiction. The sort of studies I want to see would compare two groups who aren't known to be distinct. An example: Group A and B evolved in different environments and should display some difference in behavior. They have different rates of intron fragments G and H Now look at apparently-homogenous group X, who do not believe they have A or B ancestry. Compare X with intron G to X with intron H and find the predicted behavior difference.
Do we have studies at that level?

Wasn't there a talk that touched on this at the last Singularity Summit? John Tooby IIRC. I don't remember if it was during his talk, the panel discussion, maybe his Q&A... I'm fairly certain at some point he (or someone) named a couple of big predictions. I'll look this up tonight unless someone beats me to it.

Edit: Here is what I was remembering. He talks about his guide to generating good psychological hypotheses through awareness of evolution at 15:00, with a slide with the 5 step plan at 16:40. His primer on evolutionary psychology is here and has an interesting example of a prediction of cheater detection at the end.

Evolutionary psychology also clearly explains why a significant portion of the human population will be homosexual.

Oh, wait. It does the exact opposite of that. Hmmm. [ETA: I admit kin selection provides a basis for saying that homosexuality might kinda not totally be evidence against the genetic origin of certain traits. It's not the kind of thing that anyone would predict if they hadn't already seen it, and my main point is about ex post rationalization.]

I certainly agree with the general conclusion that natural selection and our specific history as social creatures has probably shaped our thinking in some ways. The central problem here is one of epistemology. For the claim, "X causes Y," there are two good ways to prove it - show it experimentally and reproducibly, or show a logical connection and rule out all other causes. The latter is harder and inferior, but it's all we've got. Let me apply this to some examples and the problems here should be evident.

Human skin is capable of enduring water heated to about 110F for an extended period of time without sustaining damage. Does this mean that our ancestral environment had a lot of hot pools of water that we needed to survive? Or is it perhaps mostly accidental? If there were evidence that the heat-resistant properties of skin were expensive to maintain, that'd go a long way to ruling out coincidence. Absent that evidence, the mere potential explanation of hot-tubbing ancestors is useless.

Men prefer women with a BMI of 18-23 or so. This appears true in Western society. It isn't true in other societies. If you had a purely genetic account of both tendencies, or if you could rule out cultural factors definitively, you can make a convincing ev-psych argument for it. But merely knowing that a preference exists is not strong evidence it is genetic, when alternative explanations are obvious. The correct answer is, "We don't know yet; we'd need to experiment."

By contrast, a preference for facial symmetry (and to a much lesser extent waist-hip ratio) is the kind of thing that seems well-supported as being genetic. People aren't too consciously aware of it. There isn't an explicit cultural value for it like there is for thinness. It has been correlated directly to health. Maybe it's random, but given that it's expensive to dislike people, and there's an obvious function and a lack of both conscious awareness and alternative explanations, it's pretty fair to say it's probably genetic.

In short, an overall useful point is probably being seriously muddied in a detour through ev-psych. Where the actual issue is the existence of a trait, the precise cause of it is less material. It doesn't much matter if confirmation bias was useful in the ancestral environment, or if it's an accidental tag-along with something that was. The important thing is fixing it, or at least being aware of it.

You should try googling ' "evolutionary psychology" homosexuality'.

Still, it seems unlikely that if we did not observe homosexuality, researchers would be stroking their chins and saying, "Hmm, we should figure out why there is no large minority of our population that is exclusively attracted to members of the same sex. I mean, isn't that weird? How would that sort of thing evolve?"

This is a really important principle. You haven't explained a thing if you wouldn't be confused by that thing's absence.

ETA: This point is very similar to one of Eliezer's observations:

Your strength as a rationalist is your ability to be more confused by fiction than by reality. If you are equally good at explaining any outcome, you have zero knowledge.

There is a subtle distinction, though. In that post, the emphasis is on noticing when your theory contradicts a reported fact. Eliezer points out that you should either modify your theory or deny the reported fact. You shouldn't fall into the common failure mode of concocting some improbable scenario in which the fact could have occurred without contradicting the theory.

I take Alicorn's point to be about noticing when your theory neither contradicts nor implies a reported fact. The emphasis here is on avoiding the failure mode of convincing yourself that the reported fact is just what you would expect to happen, given your theory.

Very true.

However, my point was more that this doesn't exactly conflict with evopsych either.

Of course, the question if evopsych actually does any useful predictions is still open. :)

I just did that, and while there are a lot of hits, I did not find anything but speculation on the matter. For example, this was the first freely available scientific paper I found on Google Scholar addressing the question. I looked at a few others but they were much the same. There are many speculations -- it would be too much to call them theories -- but if there is actual evidence settling the matter, or even just substantially favouring some hypotheses above others, I did not find it.

On the wider internet the first two hits are junk. Seriously written, but junk. The third reports a test of the theory that homosexual men provide extra care for their relatives. It finds that in the one culture studied such an effect is present but not enough to offset the evolutionary cost of not reproducing oneself. The fourth reports another test of the kin support hypothesis, that failed to support it.

So, I have looked, and found no successful evolutionary explanation of homosexuality.

Did you have some expectation about what that Google search would find, or were you just suggesting that it would be informative one way or another on the subject?

You may already be aware of these papers by Andrea Camperio-Ciani. The first one made a pretty big splash a few years back.

Certainly not evolutionary psychology - just good old fashioned genetics (pedigree analysis). And not an explanation of why homosexuality evolved, but a plausible explanation of why natural selection has not ruthlessly eliminated it.

To my mind, the big problem with evolutionary psychology is that it displaces this very straightforward kind of science. It achieves success, not by finding truth, but rather by finding an appealing story. Kinda like religion.

To my mind, the big problem with evolutionary psychology is that it displaces this very straightforward kind of science.

To my mind, the big problem with evolutionary psychology is that it tries to boil everything down to advantages to DNA - and usually pays insufficient attention to the possibility that memes are what have benefitted instead.

To my mind, the big problem with evolutionary psychology is that it displaces this very straightforward kind of science. It achieves success, not by finding truth, but rather by finding an appealing story. Kinda like religion.

To put it mildy: I did not think this was a good argument.

Touche. It is possible to explain almost anything ex post. Moreover, it's really unclear (and what I've read does not address) how a gene that causes someone to not reproduce gets passed on. Assuming that just you have the gene and your relatives don't, it's beneficial. But if you all have the gene, that's a very different story. A gene that causes me to sacrifice myself to save my brothers is conditional - it doesn't matter unless the need arises. A gene that causes me to prefer non-procreative sex doesn't seem conditional in the same way - it simply prevents me and anyone who has it from reproducing.

In short, while one can rationalize the behaviour as advantageous ex post, it's rather hard to actually put that together cogently, and it's a very long way from getting rid of, "largely accidental" as an alternative explanation.

I will admit bias on this issue, having dated a woman with a lesbian identical twin.

Homosexuality could be controlled by environmental factors and appear at a good rate for kin selection while being genetically present in more people.

Here's a more straightforward fictional example: In Elcenia, there's a type of natural magic-user called "lights". They have healing magic - really heavy-duty healing magic, equal to or better than modern Earthly care in most respects and infinitely cheaper. However, lights can't heal themselves or each other, so it's not such a great thing to be a light - you're much more likely than the people around you to die of disease or injury. But it's really, really useful to have a close family member who's a light, because they'll heal you when you get sick or hurt. So what happens in practice is most people in species where lights appear have the necessary genetic component, but only about 1-2% of the population depending on region encounter enough ambient magic in the womb to turn into actual lights.

I get the underlying theory just fine. It's a neat fictional example, but (and I'm not familiar with the underlying fiction) it would probably be extremely fitness-enhancing. A male light would probably be incredibly high status and have little difficulty producing offspring. If it were purely genetically determined, it seems like it'd be pretty hard to sustain - no one would want it for their own children. If it were recessive, it might work out better, but there still seems a substantial problem of free-loading.

Thus, this evolutionary explanation for homosexuality partly undermines itself: it's genetic, but it's not quite genetic and there's other stuff going on that determines whether or not it gets activated. So it's either genetics (actively-selected) + environmental factors or genetics (random noise) + environmental factors. That's not a very clear case for kin selection, to say the least.

My claim isn't that it couldn't possibly be related to kin selection. It's that, like many ev-psych claims, the evidence for "or something else is going on" is far too strong to make a definitive claim, particularly because the outcome is the exact opposite of what you'd expect from simpler evolutionary theory. Otherwise, you risk combining two theories in a way that can explain far too many outcomes. Any individual who fails to reproduce can divert resources to his siblings. You could just as easily say many negative traits that don't show up with absolute consistency are also advantageous. This seems like a stretch.

In retrospect I will admit that this example detracted from my overall point and was poorly chosen.

I will admit bias on this issue, having dated a woman with a lesbian identical twin.

That... has a lot of potential.

Heuristics and biases

Human reasoning is subject to a long list of biases. Why did we evolve such faulty thinking processes? Aren't false beliefs bad for survival and reproduction?

Many researchers suggest that while humans are poor at formal logic and Bayesian inference, humans display a kind of 'ecological rationality'.

Other researchers think that our rationality is a direct result of our need to convince others that we're right, and that many of our biases (e.g. confirmation bias) are a direct result of this. http://www.edge.org/documents/archive/edge342.html

Edit - please disregard this post

Haven't read the post yet, but reporting an odd interface behavior:

When I follow links to this post from the "recent posts" sidebar, it works fine

When I follow links to this post from individual comments in the "recent comments" page, I get a "Forbidden" page. The url is different in this case as well: http://lesswrong.com/r/lukeprog-drafts/lw/5bw/your_evolved_intuitions/ rather than http://lesswrong.com/lw/5bw/your_evolved_intuitions/. This is true for both recent and early comments.

Links to other posts from individual comments work fine.

For example, it seems unlikely that we evolved a mechanism that gives us reliable intuitions about the metaphysical possibility or impossibility of zombies.

It's outside the scope of your article, but one thing that I find curious is that people nonetheless do have strong intuitions about philosophical questions for which natural selection wouldn't instill an intuitive answer. Since these intuitions aren't shaped by natural selection, different people, even within the same culture, can have very different intuitions on the same question (e.g., A-theory vs. B-theory of time). Nonetheless, each person feels that his or her own intuitive answer is almost unavoidable. Whence these intuitions and our strong confidence in them?

It seems to me the idea that essentialism evolved for dealing with creatures is a bit too narrow; certainly we don't use it just with creatures, and to the extent it works it does work more broadly than that. I would expect it would more have to do with general factors like speed and scalability (as Eliezer points out in Neural Categories).

Heuristics and biases

Human reasoning is subject to a long list of biases. Why did we evolve such faulty thinking processes? Aren't false beliefs bad for survival and reproduction?

Given the nature of evolution and the fact that perfect Bayesianism is computationally intractable, the thing to be explaining is not how bad our reasoning is, but how good it is.

Given the nature of evolution and the fact that perfect Bayesianism is computationally intractable, the thing to be explaining is not how bad our reasoning is, but how good it is.

I'd say there is time to do both.

When looking at biases I find it useful to distinguish between the ones that are the outcome of our reasoning 'just not being good enough' and those where sound reasoning appears to be actively sabotaged. Those cases where evolution spent extra optimization power introducing mechanisms that hinder the formation of correct beliefs due other selection pressures.

Of course we can also spend time explaining how good human reasoning is, either for the sake of saying "Rah! Humans" or for the purpose of developing our own optimisation processes. The two quests for knowledge are hardly mutually exclusive.

Pompomtime! Go, Humans! Hehe.

We'll need to know both to decide just which biases we want to keep, if any.

Edit - please disregard this post

As Eliezer demonstrated in this example here what you call Essentialism doesn't just apply to creatures.

Even someone who has read Richard Dawkins rant against essentialism

This is kind of a jarring use of the word "rant". Dawkins's argument seems calm and well-reasoned. (Except where he says "Indeed, every one of the series was the child of its neighbor on one side and the parent of its neighbor on the other...". Wouldn't there be at least one animal in the series who was the parent of both its neighbors?)

Okay, fixed. 'Rant' doesn't have a negative connotation for me.

Thanks. I should have mentioned that this article is yet another excellent contribution from you, notwithstanding my petty nitpicking.

This is a good explanation for (some of) the lack of progress in philosophy.

And as it turns out, all these predictions are correct.

Sarcasm, or accidental humor?

These postdictions are not predictions, I challenge you actually pose a testable prediction/hypothesis for this pseudo-science or provide real reliable examples. "Just so" stories is an excellent category for this "science".

"There is a broad consensus among philosophers of science that evolutionary psychology is a deeply flawed enterprise...Evolutionary psychologists generate evolutionary hypotheses by first finding apparent design in the world, say in our psychological make up, and then presenting a selective scenario that would have led to the production of the trait that exhibits apparent design. The hypotheses evolutionary psychologists generate, given that they are usually hypotheses about our psychological capacities, are tested by standard psychological methods. Philosophers of biology challenge evolutionary psychologists on both of these points" - Stanford Encyclopedia of Philosophy

These postdictions are not predictions, I challenge you actually pose a testable prediction/hypothesis for this pseudo-science or provide real reliable examples. "Just so" stories is an excellent category for this "science".

What about the prediction that people would (statistically) sacrifice themselves for three brothers but not one, or for nine cousins but not three? Would this qualify, provided that these specific numbers were empirically observed? After all, no competing theory makes such precise numerical predictions, to my knowledge. So, if observations were to bear out these numbers, then that would provide strong Bayesian evidence for the evolutionary origins of this kind of altruism.

Also, some of the things that you're calling "postdictions" are not universally acknowledged to be facts — e.g., claims about psychological differences between men and women. So, to the extent that convincing empirical evidence for these differences ultimately arises, wouldn't that qualify as an honest prediction of evolutionary psychology?

Could you find examples of societies who act differently? Yes. Can culture twist/avoid Kin altruism? If so, I can also invent an evolutionary story to fit that culture just as easily. Does EP explain all of these different cultures via natural selection? I did not find any so far. Evolutionary biology always seems to "explain" a narrow provincial behavior and always in postdictions.

What is satisfying? Something accurate enough avoiding ambiguity, taking in account of all of the facts & and provoing an accurate account of the actual cause of behavior (different cultures, sociology, different possible causes - i.e. actually proving it's bio-psy-evolutionary roots that drive such -detailed behaviors- & not local cultures). I could understand wider impulses as relatively probable & testable, but "sacrifice themselves for three brothers but not one", that is one huge kind of a detalied leap. Since when by the way observation is enough? You need to determine the actual cause from all the other possible ones.

I find this to be a major obstacle for the success of this enterprise as a science.

Would it help to know you could generate altruism in robots just by putting them in a simulation of evolution?

Would it help to know you could generate altruism in robots just by putting them in a simulation of evolution?

If I put them in a simulation of group evolution do you think I could make them eat each other's robot babies?

My guess is that simulations of group evolution have already been done with agent based models with simple agents (relative to the both us and the robots they were modeling in the article the grandparent linked). I would guess the answer to your question is yes, and if someone has already done something with these simpler agent based models and made group evolution appear, then I would put a fairly high probability on that 'yes.'

And if no one's done it, that just makes me want to do it...

and made group [selection] appear

The eating each other's babies thing is what you get when group selection doesn't appear.

But yes, simulations of primitive agent models in this sort of context has been done to death. Even before they did experiments with actual living creatures!

I've done this kind of experiment myself - more or less as play or tinkering with my research tools. And not so much baby eating as replication suppression via within-group sabotage. (My Masters work was in nature inspired collective intelligence. So not trying to be simulation of reality but relevant in the opposite direction.)

What I found curious (or amusing) was that they were doing it with actual robots. Something about it just seems so cute. :)

The eating each other's babies thing is what you get when group selection doesn't appear.

Is that right? I may be misremembering, but I thought that the eating babies thing was a result of group selection. Eating babies arose when a group was under group-selection pressure to have a smaller population. The group complied with the pressure by having individuals within the group consume babies within the group. It was just that the individuals ate the babies of other individuals, thereby acting in accord with both the group-selection pressure and with an individual-selection pressure.

The eating each other's babies thing is what you get when group selection doesn't appear.

Ahh, that's right.

What I found curious (or amusing) was that they were doing it with actual robots. Something about it just seems so cute. :)

I was disappointed when I read the article because it said they were doing it with models of the robots in a simulation. Real robots would have been infinitely cooler (and probably too impractical).

They checked their simulation occasionally by using real robots with the same programs ever so often.

That's closer, but unfortunately, that does nothing for my "coolness" sensors. I'm imagining a room filed with robots constantly reproducing and dieing, while interacting in interesting ways. I kind of want a room where this is going on in my house...

Now I'm imagining a residence rigged up with a robot-friendly Habitrail network.

YES! That's definitely the sort of thing I'm thinking of!

I could understand wider impulses as relatively probable & testable, but "sacrifice themselves for three brothers but not one", that is one huge kind of a detalied leap. Since when by the way observation is enough? You need to determine the actual cause from all the other possible ones.

You are right that the "three brothers but not one" bit is detailed. That is why observing such specific numbers would provide strong support for the theory, even if you didn't "determine the actual cause from all the other possible ones". Mere observation is enough. That is the essence of Bayesian epistemology.

In general, suppose that a theory T says that a highly-specific (and hence a priori improbable) observation E is likely, and then E is actually observed. Then that observation makes the probability of T increase by a very large factor. And the probability of T increases more, the more specific E is. In symbols, if p(E) is small, but p(E|T) is large, then the ratio p(T|E) / p(T) is very large. This is a direct corollary of Bayes's theorem: p(T|E) = p(T) * p(E|T) / p(E).

Note that this applies even if you merely observed E, but didn't determine what caused E to happen. (However, if you subsequently did determine what caused E, and that cause differed from what T said it would be, then T would lose whatever favored status it had gained.)

Simplified & short;
If P, then Q. Q. Therefore, P.

The question remains, postdictions or predictions? I observe a certain group of people in a culture doing something, then I postdict it with EvPsy or alien control. I observe many people dying around age 80. My theory is that if alines exist, they kill people around age 80. A postdiction with observation, is utterly worthless. It is "just so" storytelling. Observation is not enough in our case, take a walk to the the faculty of sociology. And yet, establishing casual links & correlations isn't important?

EvPsy have no apparent correlation to these behaviors, or cultures who motivate/shape them. Can you think of any falsifiable test for this explanation? Is this science?

There have been others explaining why "If P, then Q. Q. Therefore, P." isn't what is going on here, and why postdictions are not so bad.

But I'd like to address another issue: there are a lot of historical examples where all the major evidence for a hypothesis was a postdiction, but the hypothesis was so simple and fit the data so well that it became accepted mainly on the power of the postdictions. The most famous example was Kepler's model of the solar system using ellipses. Based to a large extent on their postdictive power, the basic elliptical model was largely accepted before Newton gave an explanation for why it worked. This example isn't perfect because the model did provide further confirmation by later astronomical observations.

Simplified & short;
If P, then Q. Q. Therefore, P.

That would be a logical fallacy. But, importantly, its probabilistic analogue is not a fallacy. It really is a mathematical fact that,

If P makes Q more likely, then Q makes P more likely.

In other words, it is a mathematical fact that p(Q|P) > p(Q) implies p(P|Q) > p(P).

I agree with you that predictions are better than postdictions in practice, but postdictions ain't nothing.

I observe a certain group of people in a culture doing something, then I postdict it with EvPsy or alien control. I observe many people dying around age 80. My theory is that if alines exist, they kill people around age 80.

First, see my final parenthetical remark in my previous comment. We already have causal accounts of why people die around 80. Alternative causal accounts (such as aliens) don't get much of a probability boost from explaining what we can already explain. In contrast, no competing theory predicts the "three brothers but not one" numbers specifically. If observations bore this out, the EvPysch explanation would not be competing with any alternative explanations.

Second, recall that I said that, when a theory says that an observation is likely, and the observation actually happens, then

that observation makes the probability of T increase by a very large factor.

That is true. Nonetheless, if T started out as very, very improbable, then even an increase by a "very large factor" will still leave T with a small probability. If epsilon is sufficiently small, then epsilon x 10^100 is still very small. Now, "Aliens kill people around age 80", starts out with a very low prior probability. So it will have to predict/postdict some very improbable observations to rise above a negligible probability.

Third, and most importantly, simply adding an improbable observation to a theory lowers the prior probability of that theory. Take the theory "Aliens kill people". Now augment the theory by adding the "around age 80" part to get "Aliens kill people around age 80". This addition lowers the probability of the theory. (Under the original theory, the aliens could be killing people at any age. Thus, the original theory would be true under a wider variety of circumstances, so it is more probable.)

In fact you can prove that the addition of "around age 80" exactly counteracts the boost that the augmented theory gets for successfully post-dicting that people die around age 80. You don't gain any probability for your theory by explicitly building post-dictions into it. In symbols, let T be the original theory, and let T&E be the augmented theory. It follows that, if p(E|T) = p(E), then p(T&E | E) = p(T). That is, if the original theory didn't make E any more likely, then observing E doesn't make the augmented theory any more probable than the original theory was prior to the observation of E. And "Aliens kill people" started out pretty improbable!

In contrast, the "three brothers but not one" numbers are not just added to EvPsych. They are deduced from simpler premises. So, if observations bear these numbers out, then that really is a big boost to EvPsych.

In fact you can prove that the addition of "around age 80" exactly counteracts the boost that the augmented theory gets for successfully post-dicting that people die around age 80.

Somehow I missed that as a relevant fact when recently trying to explain this stuff to a Popperian. Thanks!

Simplified & short; If P, then Q. Q. Therefore, P.

While propositional logic may be a special case of Bayesian reasoning, the Bayes's theorem formalization of the scientific method cannot be usefully reduced to propositional logic.

Also, welcome to Less Wrong!. It sounds like you may want to check out Bayes' Theorem and/or Technical Explanation.

Thank you for the kind welcome. Will read.

Actually, it's:

If P, then Q is plausible. Q. Therefore P is plausible.

And it's a valid argument in probability theory as extended logic; see the first chapter of Probability Theory: The Logic of Science, which is available on the linked webpage.

I think your conclusion is largely correct, but I see a lot of overconfidence here, particularly in the evolutionary psych section. The selish gene theory was a good one, but wrong (see epigenetics).

Overconfident? Really?

  • "...looks like a good candidate for an evolved intuition"
  • "Many researchers think..."
  • "Many researchers suggest..."
  • "Our brains may have evolved..."
  • "but we may not have evolved..."
  • "...it seems unlikely that..."

And of course I haven't defended selfish gene theory.

An exercise in parody:

  • The bacterial flagellum looks like a good candidate for an intelligently designed structure.

  • Many [non-biologist] researchers think Intelligent Design has explanatory value.

  • Many [non-biologist] researchers suggest Intelligent Design is scientifically useful.

  • Our brains may have been intelligently designed to...

  • but we may not have been designed to...

Evolutionary psychology isn't as catastrophically implausible as ID; hence the bit about parody. The point is that merely using qualified language is no guarantee against overconfidence.

merely using qualified language is no guarantee against overconfidence

No, but qualified language by itself is no basis for an accusation of overconfidence, if it is not accompanied by overconfident probabilities. The 'qualified language' is the only indication I see in the text of degree of confidence, and it indicates a general lack of confidence, and so I don't see on what basis [EDIT:] neq1 is [/EDIT] making the accusation.

I'm actually not making an accusation of overconfidence; just pointing out that using qualified language doesn't protect against it. I would prefer language that gives (or at least suggests) probability estimates or degrees of confidence, rather than phrases like "looks like" or "many suggest".

ID theorists are more likely than evolutionary biologists to use phrases like "looks like" or "many suggest" to defend their ideas, because those phrases hide the actual likelihood of ID. When I find myself thinking, "it could be that X," instead of "because of A and B, X is likely," I suspect myself of being overconfident, and I apply the same heuristic to statements from other people.

Sorry, "you're" above refers to its great-grandparent. Will edit.

And as it turns out, all these predictions are correct.

The selish gene theory was a good one, but wrong (see epigenetics).

I understand 'the selfish gene theory' to be the idea that we should expect to see genes whose 'effects' are such as to cause their own replication to be maximized, as opposed to promoting the survival/reproduction of the individual, group or species, whenever these goals differ.

This is almost a tautology, modulo the tricky business of defining the 'effects' of a particular gene.

I don't see how the existence of epigenetic inheritance has anything to do with it, especially as the selfish gene theory doesn't depend on genes being made of DNA, only that whatever they are, genes can preserve information indefinitely.

Genes just aren't as much of the story as we thought they were. Whether or not a gene increases fitness might depend on whether it is methylated or not, for example. Until recently, we didn't realize that there could be transgenerational transmittance of DNA methylation patterns due to environmental factors.