Tuesday, 29 April 2014

Processing speed and intelligence

Is processing speed simply a domain of intelligence testing, or is it a fundamental cause of the behaviours we call intelligent?

Do we get different results and insights about processing speed depending upon whether we use digit-symbol substitution tests, reaction time tests, and inspection time tasks?

Is processing speed a general and stable finding across sensory domains and central processes?

What are the neural foundations of processing speed differences?

These pesky questions have been set by Stuart Ritchie, and I am going to hear what 10 expert researchers think about these matters when they meet in Edinburgh tomorrow. However, you can help me by giving me some answers, or some questions you would like asked.

Or you could just count the number of f’s in this posting.

Monday, 28 April 2014

BBC to mention intelligence


Intelligence: Born smart, born equal, born different


At 11 am tomorrow Tuesday 29 April the BBC will be doing a program on intelligence led by the journalist Martin Sixsmith. It will be one of three on intelligence.

I have no idea what this will be like, but since intelligence researchers often gripe that their work is not well presented even in serious media, this is a chance for all of us to be pleasantly surprised.

BBC Radio 4, for those who are not in the UK., is best described as……..radio for the intelligent listener. The audience has also been described as aging or aged or middle class or not very diverse. On a good day Radio 4  is brilliant.

Sadly, I cannot turn on the wireless at that time to listen in because I will be on one of those new-fangled flying machines heading for an intelligence conference in Edinburgh (about which I hope to post something).

Can you let me know what the program is like?

Elsevier Publication versus your own blog


The journal Intelligence is published by Elsevier and I do not wish them any harm for supporting this publication. Indeed, I am happy that I was able to be the Editor of Intelligence Volume 41, Issue 6 November/December 2013 ISSN: 0160-2896 Special Issue: The Flynn Effect Re-Evaluated.

And thereby hangs a tale. After about a year of work, much of it made harder by my total unwillingness to utilize the clunky Elsevier editing system, I managed to complete the issue. It has been well received and one paper on the intelligence of the Victorians (which I had independently created some publicity for) was very heavily downloaded.

As you would expect of me, I wrote a cheery introduction to the delights within the special issue and now Elsevier has sent me the downloading figures (July 13-March 14) for my editorial. I hasten to add that I tried hard to make the introduction interesting.

Total article viewings as shown on the Article Usage Dashboard were 180. Not bad for an introduction which most people might understandably skip.

Intrigued I went back to my own blog figures and found that the same article  in the same period on my blogspot had been viewed 282 times.

Possibly there is an effect of a pay-wall (one must be open to all hypotheses) but it is interesting that the fine-tuned PR machine of a major, long-established academic publisher can so easily be surpassed by the loyal readers of an obscure blog.

(By looking at it again by clicking on the link below you will quickly make the contrast in viewings even bigger).


LCI14 Conference proceedings Kenya Kura

(Here is the abstract, as promised, and I will attempt to get the fuller presentation later).

Learning Without Questioning –Why Asians do not win Nobel prizes

Kenya Kura1

1Faculty of Economics and Information, Gifu Shotoku Gakuen University, Japan

Asians (Chinese, Koreans, and Japanese) are supposed to have higher IQs (about 105 on average) than North Europeans (100), while sciences have been developed overwhelmingly by Europeans and their offshoots. Why Asians are lacking in scientific success might relate to two factors:

1. Low curiosity, which is expressed by lower Openness to experience (-.59 SD) as shown in various cross-cultural personality comparisons.

2. Collectivism, which is captured by various individualism-collectivism indices such as the Hofstede individualism index (IDV), or Hofstede and Triandis individualism index (about -2 SD). The genetic underpinnings for these traits, such as DRD4, 5HTTLPR, and OPRM1 have also become increasingly apparent.

To integrate these psychological traits, a “q” factor is constructed by factor analysis on measures of Openness and Collectivism, which are then correlated with variables measuring academic achievements and also student assessments. It is found that IQ scores coupled with “q” factor scores neatly predict racial scientific achievements and also world-wide student assessments. 

LCI14 Conference proceedings Emil Kirkegaard


Immigration in Denmark and Norway

Emil O. W. Kirkegaard

I acquired data from the official Danish statistics agency for 71 immigrant groups by country of origin. Then I looked at crime rates, educational attainment, income and use of social benefits among the groups. There were large differences. The results show that performance on one socioeconomic measure correlated highly with performance on the other socioeconomic measures and that there was a strong general socioeconomic factor.

(Below is the link to the whole presentation)



I used regression analyses to see how well the group differences were predictable from national IQs, GDP and Islam prevalence in the home country. Surprisingly, Islam was a best predictor for all areas, while national IQs and GDP were also good but not independent predictors. Islam and IQ/GDP are combinable in multiple regression to yield very good predictions at the group level, with a R2 adjusted around 0.7 -- very high for sociology.

Lastly, results showed that the groups that did well tended to do so for both countries, as performance in one country was a good predictor of performance in the other country.

The presentation is based on three papers two of which have already been published in the open access, mandatory data sharing journal Open Differential Psychology. Some of the data is from a paper in review, also in the same journal. As the datasets are public, curious readers might want to try their own preferred predictors of socioeconomic measures for Denmark and Norway.


Emil Ole William Kirkegaard, stud.cand.mag (Aarhus University, linguistics)
emilkirkegaard.dk personlig hjemmeside / personal homepage.

Sunday, 27 April 2014

#LCI14 Conference proceedings Dimitri van der Linden


The General Factor of Personality (GFP): Its Current Status and its Presumed Relation with Life history Strategy

Dimitri van der Linden1

1Institute of Psychology, Erasmus University Rotterdam, The Netherlands

It is widely acknowledged that a general factor of intelligence (g) exists in the domain of cognitive abilities. The implications of this general intelligence factor for various life outcomes have now been confirmed in numerous studies (Jensen, 1998; Hernstein & Murray, 1996). In the domain of personality however, the existence of a general factor to date remains a rather controversial topic with many questions yet to be answered. The notion that a general factor of personality (GFP) exists is not new as it was already mentioned by Galton (1887), and after that by several others (e.g., Hofstee, 1993). Yet, systematic research on the GFP started from 2007. The GFP emerges from the intercorrelations of lower-order personality dimensions and consists of a mix of socially desirable traits. One of the leading explanations for the GFP is that it reflects social effectiveness (Loehlin, 2012). Specifically, high-GFP individuals may have the knowledge and ability to display socially desirable behavior that increases their chances of reaching social goals (e.g., attaining high social status, obtaining a mate). As such, some researchers have proposed that there may be quite some overlap between the GFP and social or emotional intelligence (Van der linden, Staousis, Petrides, 2012). It has also been proposed that the GFP is one of the manifestations of the so-called life history strategy (Rushton, Bons, & Hur, 2008). Life history theory provides a mid-level evolutionary account of reproductive strategies in which a fast strategy indicates a tendency for high mating effort and relatively low parental investment, whereas a slow strategy is associated with relatively low mating effort and high parental investment. The life history strategy is assumed to be related to a wide range of individual differences. Figueredo and Rushton (2009) argued that “…the conditions favoring slow life history strategy are those favoring the cooperative sociality of the GFP.” (p. 556). In this presentation I will provide a overview of the current status of the GFP and will address several questions and predictions arising from the notion that the GFP and Life History strategy are related. For example, one prediction is that the GFP should be associated with cognitive intelligence (the g-factor). Evidence on this topic is mixed. Another prediction is that the GFP would be related to a range of other Life History indicators. Evidence on this topic is stronger as it has been confirmed that the GFP consistently relates to validated measures of Life History strategy such as the Arizona Life History Battery or its short form, the Mini-K. From Life History Theory it can also be predicted that the GFP will have a genetic component indicating that it was under recent evolutionary selective pressure. Recent evidence supports this prediction. For example, Verweij et al. (2012) found that direct inbreeding indicators were negatively related to the GFP. Finally, there may be group (or national) differences in the GFP that are in accordance with group differences in Life History Strategies.








Friday, 25 April 2014

#LCI14 Conference proceedings Guy Madison


Increasing simple reaction times demonstrate decreasing genetic intelligence in Scotland and Sweden



There is a paradox in that although more intelligent people tend to have fewer children than less intelligent people, more recent generations tend to perform better on tests of psychometric intelligence. Since intelligence is highly heritable, this differential fertility would predict a decrease in IQ in the general population. The apparent IQ increase, known as the Flynn effect, is assumed to have environmental causes, such as schooling and the focus on abstract categorization prevalent in an information society. In other words, two different processes are simultaneously working in opposite directions, and it is then impossible to separate them when measured with the same instruments, typically paper-and-pencil matrix reasoning tests. Here, we show that change in genetic intelligence can be estimated, independently of the Flynn effect, by way of simple reaction time (RT). Data from three studies with different samples from Sweden, UK, and USA converge at an RT increase of 0.7-0.9 ms per year, which corresponds to a decrease in intelligence of between 4 and 5 IQ points per generation, or 1.3-1.7 points per decade in these countries.

This will have implications for educational attainment

Thursday, 24 April 2014

Do educated brains recover from injury faster?


The results on a sample of 769 brain-injured patients appear to be very dramatic: after a year a good recovery was achieved by 9.7% of those with fewer than 12 years of education, 30.8% with up to 15 years of education, and 39.2% with more than 16 years of education (p 0.001). The education effect held up in a logistic regression model controlling for age, sex, and injury- and rehabilitation specific factors. The authors concluded that educational attainment was a robust predictor of 1-year recovery even when adjusting for those other prognostic factors. A dose-response relationship was noted, with longer educational exposure associated with increased odds of recovery. This suggests that cognitive reserve could be a factor driving neural adaptation during recovery from traumatic brain injury.

Eric B. Schneider, Sandeepa Sur, Vanessa Raymont, et al. (2014) Functional recovery after moderate/severe traumatic brain injury: A role for cognitive reserve?

Not one of their references makes a mention of intelligence nor of cognitive epidemiology, so I was intending to make nothing more than a small but useful point that the differences between the groups go far beyond that of being exposed to education, or benefitting from education, in that they very probably largely reflect prior intelligence differences. So, for “cognitive reserve” read “intelligence”. Intelligent brains recover better.

However, there is an unremarked confound: the poorly educated slow recovering group are 52% white, the moderately educated better recovering group 72% white and the most educated fastest recovering group 82% white. This is because the white subjects were far more likely to have further education than Black and Hispanic patients. How do the authors deal with this?

Well, they report it in Table 1 but do not put it into the regression model as a factor. It would appear that if the patients had been classified by racial background there would be significant differences in their recovery rates. “White people recover faster from brain injury” is an equally supported conclusion to the “Educated people recover faster from brain injury”  headline this paper has generated. It would have been better to have sorted this out and dealt with the race confound. One approach would have been to do the extra work to see if the patient’s scholastic attainments on national exams could have been traced. Since most of them probably sat some sort of exam at 12 or 13 years of age this would have been feasible. It would have provided an even more sensitive measure of ability.

The authors go through the chore of explaining the limitations of their study. The make the following points:

“First, it is important to acknowledge that educational attainment is a surrogate, and not a direct, marker of cognitive reserve. While available published research supports the construct of education as a marker of reserve, it remains unclear whether higher educational achievement is causatively linked to greater cognitive reserve, results from it, or both. Educational attainment itself is not solely reflective of intellectual or cognitive abilities. Motivation to succeed and self-discipline, as well as socioeconomic status, are likely also associated with higher levels of education and may have important roles in determining the degree of post-traumatic brain injury recovery.”

I would have liked them to have looked at Deary’s work on cognitive ageing for a background on the intelligence component in health.

This is not a bad study. There is a good sample size and good descriptive statistics. There is an unexplored confound with race, which could have been sorted out. Of greater importance is the even bigger lack of discussion about the link between cognitive “reserve” and cognitive “power” aka intelligence. Making that link could turn out to be very informative for both intelligence and for brain research.

#LCI14 More questions for researchers


By tomorrow I hope to be able to get intelligence researchers to pay even closer attention to your questions, so please keep them coming. For example, we currently have the unanswered question: how does one increase conscientiousness? There is now a new answer on the question of genetic regression to the mean from Michael Woodley.

If you live in London let me know if you would prefer to put the questions directly to the researchers yourself.

Tuesday, 22 April 2014

Nature and nurture: Rosalind Arden replies


Dr Rosalind Arden has investigated whether the concept of general intelligence, usually seen as exclusively human, can be found in apes and dogs, and finds positive results. This is interesting in its own right, and also useful in refuting the argument that “g” is just an artefact of the intelligence tests used in factor analytic studies. I will try to get her to report more about her work on dogs next week.

In the mean time, here is her note replying to the general question as to how researchers in the field see the topic of nature and nurture, and whether it is worth continuing to research it.

Nature and Nurture

The standard statistical methods in behavioural genetics (the field in which nature and nurture are empirically tested) quantify the proportion of differences among a measured population (at a specific point in time) on a given behaviour, characteristic or trait. This gives results such that differences among people are (for example) 60% genetic and 40% environmental.

What does the average reader make of this 40%? What do we mean by the ‘environment? Most people I work with seem to assume that: we don’t know exactly, but it is something to do with the world out there. That may be true, and there may be significant elements of the world out there that do contribute to such differences (such as acute infections in childhood). But we have done a woeful job of finding out just how much of this ‘environment’ could be random biological developmental noise, rather than the environment 'out there in the world'.  One place to start with this question is to measure the variability of specified traits within a population of organisms that share the same genes.  Work like this has been done - researchers have examined variability within such 'isogenic' populations, but their findings have not been much discussed in relation to the meaning of the 'unique environment' in human studies.

The potency of Nature is often misunderstood. Knowing that the differences in trait X between people are caused 60% by genes does not tell you that genes determine 60% of trait X in Jane or Jimmy. As others have said, a heritability estimate is not a ‘gene-o-meter’. Heritability is a population level statistic, not an individual metric. Nor is knowing the population-level estimate of genetic influence on psychological traits (such as intelligence) very informative about limits (such as Jane/Jimmy could never get A levels’ or ‘would be assured A levels’) because there are so many other determinants of getting A levels. These include aspects of the external environment – and other traits in Jane/Jimmy (such as propensity to be excited by work, having friends who encourage work, and so on).

It’s rarely useful to ‘know less’ (the alternative to knowing more); so learning more about nature and nurture is a good thing. There is great consensus among scientists who conduct empirical work in this area about the value of knowing more - which is encouraging. Pretty much everyone I know: shares the view that learning about ‘the causes of traits’ is a work in progress, has some humility about what we know, and is keen to learn more.

Rosalind Arden

Monday, 21 April 2014

A researcher replies


Why don’t Northeast Asians win Nobel prizes?;
Genius - being a highly original thinker - is predicted by a combination of high IQ (which the Northeast Asians have) but also by a certain personality trait profile which distinguishes the 'genius' from the normal academic. The Big 5 pesonality factors are Agreeableness (Altruism), Conscientiousness (impulse control), Extraversion (feeling positive feelings), Neuroticism (feeling negative feelings) and Openess-Intellect (a combination of creativity and intellectual curiosity). The normal academic has high Agreeableness and Conscientiousness (that is low psychopathology). The genius, in general, has high psychopathology (ie low Agreeableness and low Conscientiousness) and high Openness. So, it is the combination of intelligence and psychopathic personality which predicts genius. Northeast Asians have very low psychopathology. This would explain why they do not win as many Nobel prizes as their high IQ might predict. 

> The evolution of racial differences in intelligence, in psychopathic personality and sporting abilities

Cold Winters theory would predict two things: that those evolved to hotter climates would have lower intelligence (as there would be lower selection pressure for it) and, in general, lower Agreeableness (less pressure to co-operatate) and lower Conscientiousness (less pressure to control impulses). These predictions are correct. Sub-Saharan Africans have relatively low intelligence and relatively high psychopathology. Cheating is predicted by psychopathic personality (low Agreeableness, low Conscientiousness) and low intelligence. As such, we would expect West Africans (for example) to be over-represented amongst cheaters in sport and there is sound evidence - currently under review - that this is the case in many sports. Chess is often seen as a sport. However, it is very much a test of intelligence and we would therefore expect poor African representation and very high Jewish representation. This is indeed the case.

Sunday, 20 April 2014

Question time #LCI14


Would you like to ask some researchers questions about intelligence?

The sorts of topics could be: Spearman's Hypothesis examined for primate cognitive comparisons; Why don’t Northeast Asians win Nobel prizes?; The Roma: a Balkan underclass; Science and its discontents; The evolution of racial differences in intelligence, in psychopathic personality and sporting abilities; Sex differences in intelligence; Polygenic selection and human evolution; the intelligence of the Victorians; Understanding heritability estimates; the General Factor of Personality, Dysgenic trends in simple reaction times in Scotland and Sweden; Immigrant attainments in Denmark; cognitive ability in Mexico; g in dogs.

Leave your question as a comment on this blog, and I will try to get an individual researcher to reply to you, either directly or through me. If you favour brevity, then tweet me your question.

Friday, 11 April 2014

Agent Pistorius


I used to be in favour of televising trials, on the basis that justice needed to be seen to be done, and that the legal process should be known to all citizens as part of their education, in case they gave evidence or had evidence given against them, or wondered why someone had been set free or convicted, or failed to appreciate the power and majesty of common law.

Now I am not so sure. Why should I be watching a trial in another country, concerning people I do not know, in a case which is unrepresentative of South Africa, a country with very high rates of murder and rape perpetrated against the anonymous multitudes? Celebrity and beauty seem to be the answer. We can be enthralled, entertained and, perhaps, educated by someone famous and someone beautiful. More than that, we can be beguiled by the redemptive story of a man who, in the harsh parlance of the past ,would have been considered a cripple, rising on magic blades to take all the prizes including the prize girl.  The populace like nothing more than to see someone rise to the stars and then fall to the ground. Even better, they get to see the couple’s private text messages. Awesome.

Milady Judge Masipa, who looks like a bright cookie, was understandably severe with the hoi polloi who chattered at the dramatic bits, telling them acidly that this was not a public entertainment, but that’s what it is. It is both a very serious trial and an entertainment. I am in the audience, complicit in the drama, as are you, dear reader, if you know anything about this case.

Everyone has a cover story. The State wants to show that pretty, high status White Folk don’t get special treatment. The Judiciary want to parade their independence, and don’t mind their 15 minutes of fame, which will buttress their profiles and do their pensions no harm. The media and their lackeys, including psychologists it must be admitted, opine. The Police have been revealed to the world as flat-footed bunglers and watch thieves, which must bring some comfort to the long suffering public, though some embarrassment to the State. Best of all, South Africa puts on a riveting detective story which might even lead to a True Confession, and which might conceivably lead people to forget that the average victim of South African crime gets far less attention and the perpetrators far less flamboyant and expensive defence barristers.

What of the psychology? First things first. Mr Pistorius’s defence is that he made an honest mistake, understandable in the context of high crime South Africa, and even more understandable in terms of White fear of violent black men in the dark, but that doesn’t need spelling out, and is best left unsaid anyway. The State has a mammoth task, because they have to prove a malicious intention, yet all the material facts from which intention might be deduced have been admitted. So, the case hinges on some very psychological but intangible factors.

Rightly, the two barristers Roux and Nel have become stars in their own right. I think I have had about 8 cross examinations as an expert witness, and probably about 20 case conferences with barristers. In my experience they are bright, quick witted, adept at dissecting language and drawing out subtle implications from statements. They try to be several steps ahead, and usually succeed. They also have a large bag full of tricks. They love side alleys into which the unwary can be drawn, for no other purpose than to reveal them to be idiots or liars. They will pounce on an obscure and irrelevant distinction and worry it to death until the poor witness agrees to anything out of pure frustration and boredom, only to have this concession turned against them on contrived grounds.  They revel in double negatives, elaborate dependent clauses, arch suggestions and tendentious interpretations. Best trick of all is Nasty Surprise. The victim, known to them as Baby Seal, is fed a comforting diet of banal questions, each answer being met by flattering agreement “Absolutely right. So very helpful. I am most grateful to you for saying that” and then a new document is produced showing that the person you are championing has some fatal flaw they have not disclosed to you, or that you have ignored vital contrary evidence in a major publication. Too late, you look back at your former replies with painful regret. Another trick is to take a specific issue and to discuss it to death so that its importance rises to dominate the case. For example, a barrister of my acquaintance, later a notable Judge, was defending a driver who was so drunk that Police decided to skip the “walk a straight line” test, fearing he would fall on the station floor and injure himself. Roydon, for that was his name, spent a long time convincing the jury that the one single test which mattered, on which the entire case must hinge, was the straight line test, and that had not been carried out. Case dismissed. The prime aim of all barristers is to secure for their client a miscarriage of justice. For the barristers the Pistorius trial is business as usual, but this time with a global audience. In some South African township hovel a young child is muttering: That’s what I want to be when I grow up.

What do we make of Oscar Pistorius? As I said in another place (see below) psychologists should not comment on people they have not interviewed. A televised trial does not give you first hand observation of a person’s face, though one certainly picks up a lot from the tone of voice. Most important, the contingencies are that Pistorius will gain considerably if his account of what happened is accepted, so his statements and behaviour cannot be taken at face value. Perhaps viewers are learning first hand some of the expensive merits of adversarial justice.

The prosecution case has centred on a theme which is a staple of criminal justice: responsibility. Perpetrators tend to minimize their actions and wish to show them as reactions. The retired prison doctor Theodore Dalrymple described a young man’s account of stabbing someone thus: “Then the knife went it”. The knife did it. The guy just happened to be there, admittedly with a knife in his hand.

Agency has a dual meaning. It can signify that you understand that you are able to operate on the world, or it can mean that you are merely an agent, carrying out a role as required. In that sense perpetrators cast themselves as victims of circumstance, agents of some higher cause, in this case the respectable home owner defending himself and his guest from intruders. 

Prison psychologists once approached me to offer trauma services to perpetrators who were traumatised by what they had done. I questioned whether this was a wise course of action, since vivid regret at their actions might possibly guide these malefactors into questioning their behaviour for ever, to the benefit of society. I said I would concentrate my scarce resources on victims.

There is an interesting issue here: how does one tell that a person is lying? The answer is simple: you need a stopwatch. Lies take longer than truth, because liars are fabricators not reporters. Fiction takes time. Ask any novelist.

Live update: Now I have just seen the prosecutor Mr Nel ask the defendant the obvious question: if Pistorius believed he was shouting for his girlfriend to call the Police while pointing a gun at an intruder hiding in a toilet, why did not the innocent girlfriend answer from behind the toilet door with a simple “Its me, Oscar”. An implication which hangs there, with Milady Judge making a note, before the Court is adjourned till Monday.

What’s my cover story? CNN asked me to comment on the trial. Otherwise I would have continued leading the search for MH370. Honestly.

Thursday, 10 April 2014

IQ, Neuroticism, booze, and those damn vegetables again


A long suffering toiler in the groves of academe writes in to say that, rather than just bemoaning the lack of intelligence and personality measures in epidemiology, I should pay some attention to a study which has done precisely that, and help boost the visibility of such work in the health literature. In fact, I have a vague recollection of the paper, but now is the time to make amends for my forgetfulness.

Bryan Pesta apologizes for the “ghastly” link below, but it is free, folks, so just copy and paste into the search bar.


By way of background, to the external world the USA is a monolith with some minor regional variations. To its citizens is a union of sovereign states, and all the better for it when that union is not too close.  Pesta, Bertsch,McDaniel, Mahoney and Poznanski (Intelligence 40 (2012) 107–114) have gathered data on all 50 American states, have found a link between IQ and neuroticism measures and health variables, and have tried to tease out possible causal links.

They found that at the State level, drinking alcohol correlates positively with exercising and eating fruits and vegetables; and it correlates negatively with rates of smoking and many chronic diseases. These data are consistent with a growing but mixed literature showing that alcohol consumption correlates inversely with chronic disease rates. This may be nothing to do with ethanol as such, but we should follow the tradition of results first, explanations later.

The authors work through the key data using multiple regression.

At Step 1, the linear combination of IQ and N alone explained 57% and 61% of the variance in Chronic Disease and Metabolic Syndrome, respectively. Both IQ and N remained significant (but attenuated) predictors of disease, after entering Health Behaviors at Step 2. Not surprisingly, Health Behaviors itself explained large amounts of variance (over IQ and N) in both Chronic Disease and Metabolic Syndrome. Note that the variance explained at Step 2 is unusually large for social science research. Fully 80% of the variance in Chronic Disease (77% in Metabolic Syndrome) was explained by the combination of IQ, N and Health Behaviors.
The size of the effects here, though, could exemplify the "high resolution" that aggregate-level data offer, relative to studies that use individuals. At Step 3 they found that IQ (Beta=−.18), N (Beta=.35) and Health Behaviors (Beta=
−.53) all remained significant as predictors of chronic disease, even after controlling for state income (Beta=−.12, ns).

Here are the correlations between IQ and :


Health Behaviours .45

Chronic disease −.51

Metabolic syndrome −.53 C

Crime −.76

Education .41

Religiosity −.55

Income .57

So, here we have a nice clean study, admittedly at State level (aggregated data) which shows the importance of IQ and Neuroticism in influencing health outcomes. Why has this engaging study only been cited once? It may be that the intelligence literature is not read by epidemiologists. Another problem may be the title: “Differential epidemiology: IQ, neuroticism, and chronic disease by the 50 U.S. states”. It is accurate but dull, and hardly worth tweeting about in its current form. I think that the Pesta gang need to get with the spirit of the age, and re-issue it with a snappier, media friendly title:

Dull worriers die sooner: Avoid West Virginia.


Disclaimer: I am sure that the denizens of West Virginia are bright and stable people. It was just a suggestion.

Tuesday, 8 April 2014

Nature, the journal, and the Nature of Samples


As you will know by now, I lead a quiet life, avoiding trouble wherever possible. The natural calm of my afternoon was shattered by a Nature News piece with the startling and quite specific headline: “Stress alters children's genomes”. As if the drama of the finding was not enough, Jyoti Madhusoodanan’s article added further details: “Poverty and unstable family environments shorten chromosome-protecting telomeres in nine-year-olds”.


They shorten the genome. Not, they are associated with shorter genomes. They take a healthy long genome and shorten it. Imagine what the shock of the headline must have done to my genome. On your behalf, I read on, undaunted. Nature had posted up a nice picture of telomeres, which is usually enough to win over the unconvinced. Ever the sceptic, I read on, and came across these prize paragraphs:

When researchers examined the DNA of 40 boys from major US cities at age 9, they found that the telomeres of children from harsh home environments were 19% shorter than those of children from advantaged backgrounds. The length of telomeres is often considered to be a biomarker of chronic stress.

The telomeres of boys whose mothers had a high-school diploma were 32% longer compared with those of boys whose mothers had not finished high school. Children who came from stable families had telomeres that were 40% longer than those of children who had experienced many changes in family structure, such as a parent with multiple partners.

At this point I wondered who would be silly enough to imagine that n=40 was a suitable basis for concluding anything, and whether anyone would be even more silly to imagine that if there were observed differences between bright and dull mothers that it followed that those differences were caused by independently existing stressful environments, rather than being due to prior differences in the genetics and the behaviour of brighter mothers.

To spell it out: dull mothers are at risk of all sorts of things, from their genes upwards and outwards; brighter mothers might be spared those risks for reasons which range from their genes upwards and outwards.

However, I knew that I must have got it wrong, because such foolish errors would never be tolerated by Nature. So I had a look at the paper.


Here is the method statement:

Initially, we identified 40 families based on a three-step process. In the first step, the sample was constrained to boys meeting the following conditions: (i) boys provided saliva at age 9 (wave 5) in-home interview, (ii) whose mother self-identified her race as black or African American, (iii) for whom no data were missing on the criterion variables described below, and (iv) who were male.

Next, we arrayed the subsample on an index of advantage–disadvantage from birth to age 9 based on an equally weighted combination of (i) family economic conditions, (ii) parenting practices, and (iii) family structure/stability.

Finally, we took children with the 20 highest scores in the disadvantaged index whose mothers had experienced at least one depressive episode and the children with the 20 lowest scores on the index whose mothers had never experienced depression. Thus, boys who scored highest on this index (n = 20) lived in homes with high levels of poverty, high levels of family instability, harsh parenting, and maternal depression. Boys who scored lowest (n = 20) lived in affluent, stable families and were not exposed to either harsh parenting or maternal depression. We then assayed the children for Telomere Length.

So, from one perspective we can say they chose a bad genetic group and compared it with a good genetic group. From another perspective we can say they chose a bad luck group and compared it with a good luck group.

What steps did the authors take to compare these two perspectives? What steps did they take to distinguish, for example, between between bad luck on the one hand and bad decisions on the other; between the slings and arrows of blind fate on the one hand and the natural consequences of damn fool decisions on the other?

As far as I can tell, none. They assume that all this bad stuff rains down on one group and that the other group is spared, but that in genetic terms both groups are identical, or close enough to warrant a comparison of the effects of these extraneous life events.

I looked up the telomere lengths and did a t test. For the harsh environment 9.6 (4.2) and for the nurturing environment 10.3 (2.5). 20 boys in each sample. Non-significant. Nowhere close. So, I presume it is only significant if you put together a model of variables to be controlled for, but otherwise not.

To my primitive eyes the sample size seems far too small to conclude anything much, and far too small for comparisons of individual gene effects. In addition, there is a highly questionable assumption that all that these boys inherited from their parents was an “environment”. Incidentally, so many fathers were untraceable in the “unlucky” group that fathers had to be left out of the whole study. A look at the genetics of the mothers would be a start. Looking at the telomere length of the mother’s DNA might also be worth a look.

Have I got it entirely wrong, and is there some innocent explanation I have missed?

I would like some assistance from anyone who can help me understand why this paper, which I think flawed, is considered suitable for publication by the editors of Nature.

Is it healthier to eat 7 vegetables or 7 scientists?


I wish no harm to the authors of “Fruit and vegetable consumption and all-cause, cancer and CVD mortality: analysis of Health Survey for England data”

J Epidemiol Community Health doi:10.1136/jech-2013-203500


whose recent publication has received approving coverage in the media. We are colleagues at the same godless institution, so they cannot be all bad. But (and you expect nothing less from me) I am not bowled over by their arguments about the benefits of vegetables. You will have caught the general tenor of my criticisms of this sort of work in “Diet is an IQ test” http://drjamesthompson.blogspot.co.uk/2013/11/diet-is-iq-test.html

Following Prof David Colquhoun, I joined him in quoting with approval a paper BMJ 2013;347:f6698 doi: 10.1136/bmj.f6698 (Published 14 November 2013) by John Ioannidis in whose train I ranted thus: “Samples of about 70,000 followed until death (with a proper link to death registers) will be required to identify even a few general patterns in diet which might account for a 5-10% increase in risk. If the studies are to mean anything, IQ, personality, sociological and occupational variables will have to enter the mix, and participants will probably have to be paid to stick to the course, and put up with random visits of inspectors looking in the fridge and the medicine cabinet.”

So imagine my pleasure, or alarm, when this paper turns out to have followed 65,226 persons drawn from a nationally representative sample for 7.7 years and visited them at home to find out what they had eaten yesterday (thus remarkably improving accuracy of their recall) and then linking the respondents to death registers. Rather disarming, isn’t it? The authors seem to have got good data without paying participants or raiding their refrigerators. The authors admit that the main limitation is that measurement of fruit and vegetable intake occurred at only one point in time and relies on self-report. There may be social desirability bias and random error (forgetting) in the recall of fruit and vegetable consumption. However, while short of perfect monitoring, this is a big step forwards. All this is very good, and shows epidemiology at its best.

Undaunted, I moved to the second half of my diatribe “IQ, personality, sociological and occupational variables will have to enter the mix”. Here I have found some things to complain about. Although they included sociological and occupational variables, they did not measure IQ or personality. Frankly, I don’t expect that of epidemiologists, because those measures are often neglected by psychologists anyway.

That aside, the authors carry on doing good things by offering us some old fashioned means and standard deviations, with participants categorized by the number of portions of fruit and vegetables they consume. These are the sorts of simple statistics I can understand. For example, the English eat slightly over 2 portions of fruit, and 1.5 portions of vegetables a day. The propaganda about vegetables has left them relatively unmoved.

Table 1 shows that those who do eat vegetables tend to have non-manual occupations, and the more vegetables they eat, the more likely they are to be in middle class occupations. Do vegetables make you rise in social class? Do bananas telephone? Do efficient compasses misdirect? (Can you spot the origin of the last two questions?)

Similarly, 7-vegetables-a-day types are much more likely to have a university degree than vegetable refusers, who tend to be less educated folk. Also, they are less likely to smoke and are more likely to be physically active. On the other hand, they are just as fat and almost as boozy as everyone else. Those who consumed more fruit and vegetables were generally older, less likely to smoke and more likely to be women, in a non-manual household, with degree level education. Veggie Mummies, yah?

Finally, when it comes to deaths during the study period, here’s the crunch: overall, 6.7% of the sample died during the study period of 7.7 years. The sad fact is that if you are 57 years old you have a 6.7% chance of being dead by the time you are 65 years old. (Or would have been 65, for pedants). Those who eat no vegetables have an 8.2% chance of death, the One to Three vegs a day 7.9%, the Three to Five vegs a day 6.4%, the Five to Seven 5.3% and the Seven Plus vegetables only 4.1%. So, although your chance of dying is relatively low, you can make it even lower by feasting on vegetables.

At first glance, the avid vegetable eaters have half the death rate of the no vegetable eaters. It suggests that vegetables are the cause of the difference. However, it could be that vegetables have nothing to do with it.

In table 2 they offer a “fully adjusted” Model 1: Adjusted for sex, age-group, cigarette smoking and social class; and the even more adjusted Model 2: Adjusted for sex, age-group, cigarette smoking, social class, BMI, education, physical activity and alcohol intake. Of course, as sharp eyed readers you will note that they do not offer a Model 0: adjusting for sex and age, the only things which are truly not controllable by individuals. That is a pity.

In table 2 they use hazard ratios, where eating no vegetables (the highest apparent risk category) is set to 1 and the other conditions lots of vegetables rates as 0.69. This certainly shows the differences with increasing consumption of vegetables, but no longer reveals absolute risk. I prefer table 1. In fact, I would have liked to have seen a correlation matrix. I can read those. I concede that such a matrix would not reveal covariance, but it would allow me to begin to think about the associations between the variables. One or two plots of data would also have helped. In my usual ferreting mode I had a look at the supplementary data.


At about 120 months the fruit effect dies out for some, probably artefactual, reason.

In both these adjusted models and in other variations the effect of vegetable consumption continues to be significant. They go into further detail about vegetables (good) and fruit (slightly less efficacious in keeping you alive) and note that canned fruit seems to slightly increase mortality, probably because of the sugary syrup in which they float.

The authors have bundled together factors that none of us can control like our age and sex, with factors we can control like how long we stay in education and the sort of work we do; with factors we can and probably ought to control like how much we eat and drink. All those different categories are “controlled for”. Some mistake, surely? I can understand the “control” for age. Older people are more likely to die in any time period than younger people. However, if I chose to become a university teacher, why “control” for that choice? I took up that occupation precisely because I thought it would be agreeable, if not well paid, and that I would be highly unlikely to suffer industrial accidents. My choice, plus my ability to get such undemanding light labour against, frankly, rather sparse competition, reveals something about me. It may explain my willingness to follow health advice, or it may simply be that I am a cautious man, minimising my risks in my personal and occupational life. A simple fearfulness of character could explain all the associations.

Consider the adjustments. These are based on the assumption that the cigarette smoking, social class, BMI, education, physical activity and alcohol intake are not related to something which itself has an influence on health. They are seen as imposed external factors which can influence health, rather than a series of behaviours related to an intrinsic factor: system integrity. System integrity is a hypothesized intrinsic characteristic which gives you a good body and a good mind, such that you are healthy and intelligent. This may be related to your genetics and/or a favourable beginning in utero. The one give-away sign of system integrity is fast reaction times to simple stimuli. See the Edinburgh group under Ian Deary for all these findings.

Seen this way, the intelligent live longer and healthier lives not because they are wise, but because they are lucky. They eat vegetables because it seems to be the clever thing to do from a health point of view, and perhaps because they can work out that the need for protein from meat is relatively small, so vegetables are more cost-effective. They may even like the taste of them. They also wear seatbelts, use condoms, brush their teeth, don’t smoke, go for walks, don’t eat or drink too much, study hard, strive to get good jobs and always save money.

The conclusion of this study is that we should eat our vegetables, and 7 portions rather than only 5. Perhaps so. It is still possible simply that bright people live longer, even when they are slightly plump and somewhat boozy. No, my gripe is about the way they have interpreted the findings, and the assumptions which underlie their calculations of hazard ratios. The authors make it clear that “This study has found a strong association, but not necessarily a causal relationship. There are additional unmeasured confounders not included in the analyses, including other aspects of diet.” However, they go on to mention other dietary factors, not the psychological ones.

Vegetables may be good for you. But I have been assured that scientists make a most delicious, nourishing, and wholesome food, whether stewed, roasted, baked, or boiled; and I make no doubt that it will equally serve in a fricassee or a ragout.