Science & Fun - Jonathan Graehl

After controlling for income, education, and social class: childhood intelligence is correlated with adulthood drinking, including unhealthy binge drinking. They should also control for adherence to religions which prohibit alcohol.

“Persistent exposure to light at night may lead to weight gain, even without changing physical activity or eating more food, according to new research in mice. Researchers found that mice exposed to a relatively dim light at night over eight weeks had a body mass gain that was about 50 percent more than other mice that lived in a standard light-dark cycle.”

It’s worth making sure you sleep in dark/quiet in any case.

memory loss has been linked with high levels of ‘stress’ steroid hormones known as glucocorticoids which have a deleterious effect on the part of the brain that helps us to remember. An enzyme called 11beta-HSD1 is involved in making these hormones and has been shown to be more active in the brain during ageing. …

human trials will start on a drug that blocks that enzyme; effects seen in mice after 10 days of dosing.

Caffeine suppresses appetite and is a stimulant.  But also (caveat: mice may differ from humans):

Coffee polyphenols suppress diet-induced body fat accumulation by downregulating SREBP-1c and related molecules in C57BL/6J mice.

I’m turning 33 soon.

the most obvious misunderstood fact of player performance: it is sharply peaked at age 27 and decreases rapidly, so rapidly that only the very best players were still useful at the age of 35. He was able to observe only one executive that seemed to intuit this–a man whose sole management strategy was to trade everybody over the age of 30 for the best available player under the age of 30 he could acquire.

That’s for baseball.  In other professions, the peak differs.  Physicists peak at 40.

Everyone is repeating “10000 hours until mastery (40 hrs/week for 5 years)” since Malcom Gladwell, but this is apparently backed by some research. Since some tasks are shallower than others, I imagine that they would need less time to become e.g. 99% as effective as at the peak. Is the time until peak really stable across disciplines?

Found via Craig Heldreth.

An example of a study that doesn’t say as much to me as to the researchers:

does our inner voice help us with impulse control?

To get at this question, the researchers asked people to do several other things while they performed the Go/No-Go task. On some trials, people had to say out loud the word “computer” over and over while they did the Go/No-Go task. Because repeating “computer” uses the same verbal resources that support our inner voice, it ties up our inner voice so it can’t function properly. If, our inner voice is important for controlling our impulses (e.g., “don’t press the button”), then it follows that people should perform worse on the Go/No-Go task when they are repeating “computer” than when they are not. Of course, to ensure that it is not the addition of any activity that disrupts Go/No-Go task performance, but specifically an activity that prevents folks from wielding the voice in their head, on other trials people performed another activity that was more spatial in nature. People were asked to continuously draw circles on a piece of paper with their non-dominant hand. Like repeating “computer” over and over, this circle drawing task is repetitive and requires some attention to do correctly, but importantly, it doesn’t occupy verbal resources so the inner voice can still function properly.

Compared with the circle-drawing task, repeating “computer” resulted in more impulsive responding. People had a greater tendency to make a ‘Go’ response - even when they shouldn’t have. These results suggest that the inner voice helps us to exert self-control by enhancing our ability to restrain our impulses.

Tullett, A., & Inzlicht, M. (2010). The voice of self-control: Blocking the inner voice increases impulsive responding. Acta Psychologica, 135, 252-256.

(the task is purely visual-motor, and “Go” happens 2/3 of the time, so the mistakes tend to be in that direction)

All this says to me is that there’s a conflict between saying a word, and performing the Go/No-Go task, which is greater than the conflict from a repetitive motion with the left hand.

It’s obvious that some things are distracting. I can’t listen to someone and read at the same time (understanding both). I can’t talk freely and read something else at the same time. It’s also obvious that many people choose to perform some repetitive fidgeting motion while they think.

They’re going to have to get much more creative if they want to convince me they have uncovered some general principle - what they wish they’d shown is that some of the verbal resources of the brain are recruited for arbitrary rule-following tasks, where an exception to the usual pattern happens enough that the initial tendency has to be overriden.

Of course humans need water for many reasons, but I was still impressed by this:

Brain cells require a delicate balance between water and various elements to operate, and when you lose too much water, that balance is disrupted. Your brain cells lose efficiency.

Years of research have found that when we’re parched, we have more difficulty keeping our attention focused. Dehydration can impair short-term memory function and the recall of long-term memory. The ability to perform mental arithmetic, like calculating whether or not you’ll be late for work if you hit snooze for another 15 minutes, is compromised when your fluids are low.

Over the course of a typical twenty-four hour period, the longest spell most of us go without fluid intake is the six to eight hours we spend sleeping. Sleeping is hardly the kind of activity that you sweat over, but that doesn’t mean you’re not losing water during the night. With every somnolent breath, you expel moisture, and the cumulative effect of a night’s sleep is to dry out.

according to Joshua Gowin, a neuroscience doctoral student.

If the “delicate balance” is important, then too much water is probably bad as well.

I’ve experienced a light headache or near-fainting spell after sitting indoors without drinking enough water. I’m pretty sure that mild dehydration is possible without feeling extremely thirsty.

Resveratrol has gotten a lot of press as a life-extender, mostly because people love an excuse to consume red wine and dark chocolate. But the expected effect of a heroically resveratrol-heavy diet on humans is probably so small as to be practically undetectable. Even in concentrated pill form, the quantity that would be equivalent to what extends nematode lifespan by 4% would be difficult to consume (and presently quite expensive).

Just enjoy the placebo effect when you munch on your dark chocolate bar and sip your red wine.

(thanks, gwern)

From the paper in the previous post:

When people expect to have to exert self-control later, they will curtail current performance more severely than if no such demands are anticipated.

Cool.

Consistent with the conservation hypothesis, people can exert self-control despite ego depletion if the stakes are high enough. Offering cash incentives or other motives for good performance counteracts the effects of ego depletion.

I also expressed skepticism that experimental subjects were really motivated.

Inducing a state of positive emotion such as humor seems to have that effect [moderating or counteracting the effects of ego depletion] (Tice, Baumeister, Shmueli, & Muraven, 2007). Having implementation intentions — formulating ‘‘if–then’’ statements about how to behave in a situation prior to entering it — seems to be effective most likely because such intentions operate as behavioral plans and guidelines that reduce the need for executive control (Webb & Sheeran, 2003). To be sure, none of these procedures clearly counteracts the depleted state in the sense of replenishing the depleted resource. Rather, they may all operate by inducing the person to expend more of the depleted resource. In contrast, there is some reason to think that replenishing glucose in the bloodstream does actually rectify the depletion by restoring the depleted resource (Gailliot et al., 2007).

Having a comprehensive plan in place means you don’t have to decide anything. Does making such a plan cost as much as making a decision in real time?

Logical reasoning, extrapolation, and other controlled processes depend on control by the self, and performance on these tasks dips sharply when people are depleted (Schmeichel, Vohs, & Baumeister, 2003).

I wonder what types of items generally used to measure IQ (“G”) don’t ego-deplete.

Recent studies indicate that the same energy is used for effortful decision making, as well as for active rather than passive responses (e.g., Vohs et al., 2007).  These seem to correspond to what laypersons understand as ‘‘free will,’’ namely the ability to override impulses, behave morally, show initiative, and behave according to rational choices (Baumeister, in press).

If I remember this research, contemplating the decision (e.g. imagining consequences) isn’t depleting; making it is.

Success at building self-control through exercises has been inconsistent.

Agreed.

Identifying the biological substrates of self-control depletion (and replenishment) would be another helpful direction for further work.

I mentioned this earlier.

Response to my post on ego depletion from Unnamed at LessWrong (who also pointed me to the research in that post):

people come into the lab, they do one task that drains their willpower, then they get some intervention that might restore their willpower, then they do another task that requires willpower. This review by Baumeister, Vohs, and Tice (pdf) lists a few that have worked and gives citations:

 

• Humor and laughter
• Other positive emotions
• Cash incentives
• Implementation intentions (‘‘if … then’’ plans)
• Social goals (e.g., wanting to help people; wanting to be a good relationship partner)

I’ll read the pdf later, but for now titrating a sweet food or drink seems like a cool willpower-boosting trick (I find that when I play beach volleyball for hours, I do better if I can have some chocolate, soda, or banana between games, but that’s probably helping with the more obvious muscle glycogen depletion).

One of the things I like about my dentist is that she’ll tell me they think there’s cavity in xray, and want to wait to see if it goes away or gets worse before treating.  I always thought: weird, can cavities really heal?  Or are they just not sure that it’s a cavity?

From NPR:

Prof. ARIELY: So imagine: You came to a dentist; you got your X-ray. And then we took your X-ray, and we also gave it to another dentist.

SIEGEL: Right.

Prof. ARIELY: And we asked both dentists to find cavities. And the question is, what would be the match? How many cavities will they find, both people would find in the same teeth?

SIEGEL: And I’d really hope it would be somewhere up around 95-plus percent.

Prof. ARIELY: That’s right. It turns out what Delta Dental tells us is that the probability of this happening is about 50 percent.

SIEGEL: Fifty percent?

Prof. ARIELY: Fifty percent, right. It’s really, really low. It’s amazingly low. Now, these are not cavities that the dentist finds by poking in and kind of actually measuring one. It’s from X-rays. Now, why is it so low? It’s not that one dentist find cavities and one doesn’t. They both find cavities, just find them in different teeth.

(Soundbite of laughter)

Prof. ARIELY: And here is what happens. Imagine you’re a dentist, and you see a patient, and you really want to find a cavity because you get paid more if you find cavities and you can fix them. And the patient is already on the chair. He’s already prepped. You might give them the treatment right now, really good marginal income for you. How is this motivation to find cavities - will influence your ability?

Now, you look at an X-ray - which is a little fuzzy and unclear, and there are shadows and all kinds of things are happening. What happens is this unclarity of the X-ray helps, in some sense, the dentist to interpret noise as signals, and find cavities where there aren’t really any.

SIEGEL: And fill them?

Prof. ARIELY: And fill them, and drill them, expand them. I don’t think they ever tell their patients, hey, I thought it was a cavity but turns out it was just a mistake.

(Soundbite of laughter)

Prof. ARIELY: But they do fill them.

SIEGEL: You’re describing a very private relationship between patient and dentist.

Prof. ARIELY: Yes.

SIEGEL: You’re telling us we should, on average, expect our dentist to be getting it wrong on the X-rays, but that’s not how people feel about their dentists, right?

Prof. ARIELY: That’s right. And the dentists actually have a tremendous loyalty. People are really loyal to their dentist, much more than other - medical profession. And I think one of the reason - go back to cognitive dissonance. Cognitive dissonance is the idea that when people do something painful, they become more committed to the goal. If we have a fraternity and we haze people in a more difficult way, they become more loyal to the fraternity.

SIEGEL: You have dentistry as a hazing experience right now.

Prof. ARIELY: That’s right. And I think the same thing happen with dentists. Dentistry is basically the unpleasant experience. They poke in your mouth. It’s uncomfortable. It’s painful. It’s unpleasant. You have to keep your mouth open. And I think all of this pain actually causes cognitive dissonance - and cause higher loyalty to your dentist. Because who wants to go through this pain and say, I’m not sure if I did it for the right reason. I’m not sure this is the right guy.

(Soundbite of laughter)

Prof. ARIELY: You basically want to convince yourself that you’re doing it for the right reason.

SIEGEL: Every visit to the dentist is an episode in the Stockholm syndrome here, is what you’re describing. You studied these dental insurance records, and you looked at what happens over time as our relationship with the dentist grows over many years, and you find it affects the kinds of decisions the dentist and the patient make, about choices.

Prof. ARIELY: That’s right. So you can imagine that at some point in your dental treatment, you have a choice between things that have the same possible outcome, but one of them is more expensive to you and better financially for the dentist. Which one would you choose, and how the duration of relationship be affecting that?

And it turns out that the more time people have seen the same dentist, the more likely the decision is going to go in favor of the dentist. People are going to go for the treatment that is more expensive but has the same outcome. More out of pocket for them, more money for the doctor. So in this case, loyalty actually creates more benefit for the dentists.

Dementia is the result of age-related damage to the brain. While there are some drugs and dietary practices that help slightly in avoiding this damage, it turns out that bilingual brains function better at the same level of damage, probably due to redundancy in connections (mediated by the different languages’ words’ connections). I have a rich monolingual vocabulary, and so expect to enjoy some similar (probably less dramatic) benefit in my senescence. Still, it may be worth my time to extend my mostly-forgotten high school Spanish into a more usable state.

The symptoms of dementia can be delayed by an average of four years in bilingual people.

Multilingualism doesn’t delay the onset of dementia—the brains of people who speak multiple languages still show physical signs of deterioration—but the process of speaking two or more languages appears to enable people to develop skills to better cope with the early symptoms of memory-robbing diseases, including Alzheimer’s.

(according to the research of Ellen Bialystok)

It’s well known that exercise of self-control drains a “battery” - studies have shown that a sequence of willpower-taxing tasks become effectively more challenging, and that the obvious alternative explanations don’t apply - the depleted resource is specific to self-regulation. One alternative I think should still be examined: repeated demands for self-control which aren’t commensurately rewarded, should rationally lead to apathy. But at least one study had a real consequence for lack of willpower: subjects overpaid with their own money, so it wasn’t the case that the tasks and their rewards were merely artificial tokens.

Baumeister et. al survey the evidence that willpower can also be generally improved by practice. It’s pretty weak, but if you’re hoping to self-improve, you can find some reasons to hope.

Best results were obtained among participants who were assigned to improve their posture whenever they thought of it. Other participants kept track of what they ate, and these showed some improvement. The group that was assigned to try to improve their mood state whenever they felt bad did not show any benefit from this exercise.

But maybe improving your posture or diet builds your willpower reservoir directly (suppose you were to do this due to pleasure in playing a sport, or having someone you love prepare better food for you, or you for them …). Still, good news either way (if it’s easy to improve posture and diet, and it leads to more willpower, fantastic).

(Oaten & Cheng, 2004a) enrolled participants in physical exercise programs for 2 months. The exercise programs included weightlifting, resistance training, and aerobics, and each participant received a program designed by a gym staff member specifically suited for him or her. A staggered waiting list control group design was used so that all participants eventually received the exercise program. The hypothesis was that adhering to an exercise program requires self-regulation, and so 2 months of such regular effort would improve the capacity for self-regulation in general.

This substantially reduced the ego depletion (where one challenging self-regulation task decreases performance on another such task immediately following it). Again, I’d think it may be physical exercise that improves the willpower battery’s capacity or usage rate, not the use of willpower in order to perform the exercise (substitute some more fun exercise program, like sex, or a sport the subject enjoys, and see what happens).

people who performed the exercise routines became more successful at reducing their cigarette smoking, alcohol use, and caffeine consumption. They ate less junk food and ate more healthy food. They reported improvements in emotional control and a reduction in impulsive spending. They reported studying more and watching less television. Even some domestic habits (e.g., washing dishes instead of leaving them in the sink) also improved across the exercise program

I would explain this with consistency and identity effects, not willpower. But this is still useful. Since this was a prospective study with (I assume) no dropouts, we can reasonably guess that the exercise in fact caused this.

only some of these behaviors could plausibly be directly linked to the exercise itself

If the above survey-based claims of generalized self-control improvement (which were not directly measured). It’s obvious that you can’t separate survey results about whether the respondent has positive qualities from changes in their tendency to signal positive things about themselves (if they exercise, they’re physically more attractive and perhaps more confident in credibly claiming virtue, and also honestly view themselves as more virtuous).

Participants signed up for a 4-month program on financial monitoring. Each participant met with the experimenter, individually, at the start, and together they reviewed the participant’s bills and spending habits and devised a personal money management plan. [Through use of diaries and logs], most participants improved substantially in regulating their use of money.

Again, the ego-depletion effect decreased in magnitude after just 1 month of following the budgeting and record-keeping regimen. And, again, survey responses indicated that people were improving their diet, reducing drug use, cleaning their house, keeping promises, and studying. This time they measured stress (PSS), distress (GHQ), and self-efficacy(GSES) also, and there was no significant difference. Identity/consistency effects can’t be ruled out, but this is finally doing a pretty good job at indicating that regularly practicing control over some part of your life has a generalized self-control training effect.

Studies showing a reduction in ego-depletion from some non-exercise, non-diet, “responsible” self-monitoring intervention do not necessarily make people feel significantly better (students following a structured studying program did feel less stress, but the budgeting exercise left people feeling about the same), and definitely don’t significantly improve GSES (self-efficacy). So the improvement is more focused, and it may be fair to call it an improvement in general self-regulation. One reason for caution: all these studies are by the same folks (Oaten & Cheng) who seem to really like the idea that willpower can be trained.

Gailliot et al 2007 test ego-depletion by presuming (evidence from Gordijn et al 2004) that overriding prejudice uses the same willpower resource; the initial task is to talk about a typical day of a particular hypothetical obese or homosexual person, while “avoiding stereotypes” (whatever that means - basically, second guess and filter your creativity when it’s too quintessential, which should be tiring); the follow up task which should suffer from ego-depletion is anagram deciphering performance (anagrams are thought to require executive function, because trying all possibilities is taxing?). People who showed low in motivation to avoid prejudice did worst on anagrams.

This doesn’t tell me much because both activities are globally tiring. Baumeister et al assumes that the thing that’s tired out is exactly “willpower”, which seems questionable to me, unless they also show, as was done with other ego-depletion measures, that performance on other metrics (e.g. arithmetic) wasn’t also degraded. Also, they seem to presume that it’s not the case that the people who tend to be good at inventing non-stereotypically are simply smarter, and thus better at anagrams. They attribute entirely to ego depletion the difference in performance between the better and worse stereotype-suppressors (the worse ones must be “trying harder”). Very sketchy.

The Gailliot willpower-practice exercise was to use the off-hand (non-dominant left/right) for everyday activities: brushing teeth, stirring drinks, computer mousing, carrying, eating, opening doors, etc. Also explored was verbal self regulation: avoid slang (e.g. “yes” not “yeah”), don’t start sentences with “I”, and don’t curse. Both exercises (followed for 2 weeks) gave an improvement in anagram performance compared to the no-exercise group, but only for those who had trouble with the stereotype suppression exercise. Perhaps this gives some evidence that the anagram task really does measure ego depletion. Perhaps this means that the only people who benefit from willpower training are those who have an unusually low amount of practice exercising it; or it may only mean that the draining preliminary task (making up a story) is just really easy for some people, so their willpower might have improved from the exercises, but the test wasn’t challenging enough to show any difference.

My largest objection to this area of research is that there’s no proposed physical mechanism or detection of these purported changes. I don’t need that kind of evidence to believe something about human behavior, but it’s extremely easy to draw the wrong conclusions from purely behavioral studies.

My next objection is that the control groups (who are assigned NO regular exercises) are poorly designed given that the followup ego-depletion test is a repeat of the initial one; those who are assigned exercises are often remembering the ego-depletion test; the control group is never reminded at all. So the control group isn’t controlling for task-specific learning/priming effects (you can definitely learn or refresh memories by visualizing/reviewing, not only by doing).

Summary: I now believe (70% likely) that people who are easily ego-depleted can train to become significantly more normal, if they’re able to institute some self-regulation habits over a long period of time (2 weeks or more). It’s unknown (50% likely) whether people who already have regular self-regulation exercise can benefit from more volume or intensity in that area. Also, (60% likely) improvements in exercise and diet (I would guess sleep also) may give better ego-depletion capacity, supplementary the fact that applying them involves exercise of self-regulation.

I have no idea if habits that involve self-monitoring and adjustment, that are easy to follow because they’re immediately rewarding or self-image-enhancing, are just as good for willpower training as things that are subjectively grueling and painful. I definitely won’t embark on any heroic efforts in that direction without stronger evidence; what I will do is ensure that I’m regularly working on changing something in my life (whatever seems most productive at the time).

There’s also some evidence that willpower can be buttressed with sugar (the brain needs glucose):

Acts of self-control deplete relatively large amounts of glucose. Self-control failures are more likely when glucose is low or cannot be mobilized effectively to the brain (i.e., when insulin is low or insensitive). Restoring glucose to a sufficient level typically improves self-control. Numerous self-control behaviors fit this pattern, including controlling attention, regulating emotions, quitting smoking, coping with stress, resisting impulsivity, and refraining from criminal and aggressive behavior. Alcohol reduces glucose throughout the brain and body and likewise impairs many forms of self-control. Furthermore, self-control failure is most likely during times of the day when glucose is used least effectively.

Spinoza:

It is the part of a wise man, I say, to refresh and restore himself in moderation with pleasant food and drink, with scents, with the beauty of green plants, with decoration, music, sports, the theater, and other things of this kind, which anyone can use without injury to another. For the human Body is composed of a great many parts of different natures, which constantly require new and varied nourishment, so that the whole Body may be equally capable of all the things which can follow from its nature, and hence, so that the Mind also may be equally capable of understanding many things.

In other words, please yourself in all ways that you can be pleased. It’s healthy. Spinoza also advises that you not injure others in pursuit of your pleasure - always a popular sentiment.

Eliezer Yudkowsky is a smart guy who also writes Harry Potter fanfic.  You should read Harry Potter and the Methods of Rationality if you’re either interested in learning about flaws in human thinking while being entertained, or if you’re already familiar with Harry Potter (e.g. you watched one of the movies).  The premise is, essentially: what if several of the supposedly brilliant characters in the source material were actually both clever and wise?

(apologies if you’re genuinely lactose-intolerant)

Meta-analyses suggest a reduction in risk in the subjects with the highest dairy consumption relative to those with the lowest intake: 0.87 (0.77, 0.98) for all-cause deaths, 0.92 (0.80, 0.99) for ischaemic heart disease, 0.79 (0.68, 0.91) for stroke and 0.85 (0.75, 0.96) for incident diabetes.

source

Heavy dairy consumers have a 0.87 relative risk for all-cause deaths compared to dairy-avoiders.   The numbers (0.77,0.98) are the 95% confidence intervals - i.e. the actual relative risk is almost certainly somewhere between 77% and 98%.  A relative risk of .87 means that you’re 13% less likely to die (only (87% as likely to) if you consume a lot of dairy than those who abstain.

This is not a prospective study, so you can’t know that increasing dairy intake now will definitely make you less likely to die.

From Art Markman (I wonder if the opening anecdote really happened to him, or if he imagined or stole it?):

One of the strangest conversations I have witnessed happened when I was at a party at a friend’s house several years ago. He was regaling me with a story about making breakfast in high school and covering the dog with pancake mix. He got to the end of the story (which was funnier than you might think) when his brother piped in. “Great story,” he said, “but that was me, not you. You were on the sofa watching.” The next 20 minutes devolved into an argument over whose life it really was.

I had forgotten about that story until I read a paper in the September 2010 issue of

Psychological Science

by Isabel Lindner, Gerald Echterhoff, Patrick Davidson, and Matthias Brand. They were interested in how observing actions influences your memory for those actions.

Previous research has shown that if people imagine performing an action, they can later believe that they did it. I know I have had this happen to me. I have thought about bringing the garbage can to the street on the day when garbage is collected. Later, I am surprised that it isn’t out on the street; I mis-remembered thinking about taking out the garbage as actually taking it out.

These authors were interested in whether observing an action can lead you to think later that you actually performed it. To test this possibility, they first had people read about a variety of simple actions like shaking a bottle or tapping with a pencil for 15 seconds. Some of the actions they only read about, while others they read about and also performed.

After a short break, people saw videos of other people carrying out some actions they actually performed, some they just read about, and some that were not a part of the first phase of the experiment at all.

Two weeks later, the participants were shown a list of actions and were asked whether they had performed them in the first session of the study.

Across three studies, people were consistently more likely to believe that they had performed actions that they had only seen someone else perform than actions they had not seen someone else perform. That is, watching someone else perform an action led people to believe later that they themselves had performed the action. This finding held up even when participants were told at the beginning of the study to pay careful attention to the actions they performed.

In a particularly interesting condition, this finding was observed even when participants were warned that people often mis-remember actions they see other people perform as things they did themselves. Knowing about this effect does not make it go away.

He goes on to speculate in a way I can’t fully support, but it’s still plausible:

Why does this happen?

As I have written about previously in this blog, when you see someone perform an action, you often adopt the goals of the people you are watching. This phenomenon is called

goal contagion. Goal contagion is useful in social groups, because it can lead an entire group to want to work together. A side effect of this goal contagion, though, is that you may later think you were more involved in an action than you actually were. The most extreme version of this effect is a false memory that you performed an action that you actually did not.

Findings like this reinforce the point that our memories are not designed to provide a truthful readout of the events of our lives. Memory is designed to help us act in the future. Seeing an action performed gives you some confidence that you understand how to perform the action yourself. Your memory is really trying to tell you that you understand how to perform an action.

Is it because people are taller than they’re (on average) more intelligent?  I doubt it.  Satoshi Kanazawa claims that the average man is smarter than the average woman, but in same-height populations, the reverse is true.  For sure the same environmental problems that would lead to below-genetic-potential height would also lead to below-genetic-potential intelligence (it’s well known that much of the variation in intelligence is explained by absence of damage from malnutrition or disease), so I don’t feel like there’s necessarily any mystery.  In fact, if a man and woman are the same height, then it’s likely that the woman grew up in a more health-promoting environment.  However, he disagrees.

He explains this data as being caused by height as well:

(not a sample) of all babies born in Great Britain (England, Wales, and Scotland) in one week in March 1958 (n = 17,419), and has followed them throughout their lives for more than half a century.  The NCDS also has one of the best measures of general intelligence in all of survey data.  They measure intelligence at age 7 (with four different cognitive tests), at age 11 (with five different cognitive tests), and at age 16 (with two different cognitive tests).  Note that the respondents are largely before puberty at ages 7 and 11, but largely after puberty at age 16.

Here are the graphs that chart the mean IQ of the NCDS respondents by sex at ages 7 and 11, before puberty.  You notice that girls are slightly but (given the large sample size) statistically significantly more intelligent than boys at both ages.  At age 7, the mean IQ for girls is 100.6 while the mean IQ for boys is 99.4.  At age 11, the mean IQ for girls is 100.4 while the mean IQ for boys is 99.6.

However, the sex difference is reversed at age 16, as the following graph shows.  Post puberty, the mean IQ for girls is 99.2 while the mean IQ for boys is 100.8.  Remember, these are the same individuals who are tested at three different ages in their lives.  (And, no, it does not mean that girls become less intelligent after puberty in any absolute terms.  The IQs are calculated and normed at each age separately.  It only means that girls become less intelligent relative to boys after puberty.)

Because of their faster rate of maturity, girls are more intelligent than boys until puberty, but the male advantage in intelligence emerges when boys are fully mature and become taller than girls.

From MIT:

Controlling for individual abilities, groups with more women had more ‘collective intelligence’ (mixture of scores on group tasks).  Average individual intelligence was about 8 times less important on some final test in 3 person groups than that group’s performance measured on other tasks (call this CI or ‘chemistry’ if you like).  Of course, CI is itself is correlated with avg. and max. individual intelligence (r=.17), but more so with avg ‘social sensitivity’ (ability to read emotions based on pictures of the eye region - you can take the online test) (r=.26), and with evenness of turn-taking in speaking (r=.4).  The female-group advantage (r=.23) is mostly but not entirely explained by the tendency of females to score higher on ‘social sensitivity’.  Turn-taking evenness is likely not a cause, but an indication of a well-functioning group where everyone is really trying.  Of course if someone is being talked over beyond their ability to persist, they will probably stop contributing, but this rarely happens.  Full paper and experimental details (from Science).

It’s interesting that the women in these studies were on average less intelligent and better at reading faces than men (both IQ and sensitivity are useful for group performance), and their presence yielded significant group performance gains.  Alternative hypothesis: a man in a group which also has women will try harder to impress them.  This could be tested by segregating the analysis by all-male vs. some-female (the same could be done for all-female vs. some male; after all it may be that women try harder in the presence of men also).