Colic psychology

I’ve just found a surprisingly psychological New Yorker article on colic, the persistent and mysterious episodes of crying that affects some newborn babies.

I always thoughts that colic was just discomfort caused by trapped wind but apparently this is just one theory and the cause of colic is still medically unexplained.

The crying tends to stop after a few months and although thought to be physically harmless it can cause a great deal of discomfort to both baby and parents.

The New Yorker article, written by the talented physician and writer Jermone Groopman, notes that some of the most important discoveries about colic have not focused on the biology of the babies digestive system but on the psychology of parenting and carer-child interaction.

Lester believes that some infants who suffer from colic are “hypersensitive to normal stimuli”: they perceive and react to changes in their bodies (such as hunger or gas pangs) or in their environment (such as loud noises or the experience of being touched) more acutely than do other babies. In the mid-nineties, he studied forty-five children between the ages of three and eight who had had colic as infants (and had been seen at his clinic). He found that thirty-four of them—about seventy-five per cent—suffered from behavioral problems, including a limited attention span, tantrums, and irritation after being touched or coming in contact with particular fabrics or tags in their clothing. “Some of the kids would get very annoyed and refuse to put on a hat,” he told me. The children apparently objected to the sensation of having fabric on their head.

Lester speculates that many colicky infants are so sensitive to stimuli that physical contact with their parents is unlikely to soothe them, a theory that may be supported by data from societies in which babies are held continuously. Ronald Barr, the co-author of the 1997 study on infant cries, has analyzed data gathered by Harvard researchers between 1969 and 1971, during a study of the !Kung San, a tribe of hunter-gatherers in Botswana who practice a version of attachment parenting. “We found that the !Kung San carry their babies upright, have skin-to-skin contact day and night, breast-feed every 13.69 minutes for the first one to two years of life, and respond within fifteen seconds to any fret or whimper,” Barr, who now teaches at the University of British Columbia, told me. “The duration of the crying is fifty per cent less among the !Kung San compared with Western babies, but the !Kung San still have what we call colic, with episodes of inconsolable crying.”

A great deal of clinical psychology work concerned with difficult behaviour in children focuses on how people respond to certain behaviours. It is often the case that our natural reactions inadvertently reinforce and maintain the problem.

This can be the case even with severe difficulties like self-harm. Imagine that the parents of a child go through a period where they are so caught up in work they don’t have much time for the child no matter what he or she does.

The child accidentally harms themselves and suddenly gets a great deal of attention because the parents, who are not ‘bad parents’, just massively overworked, want to make sure their child is OK.

The child works out that harming themselves gets them attention but this causes resentment, so the parents act more negatively towards the child he or she does not harm themselves, meaning that caring attention is all the more attractive.

Although this type of cycle is most likely to crop up with children with learning disabilities, you can see how less severe versions (replace self-harm with tantrums) could easily occur. Or perhaps how the same cycle could occur in a child with learning disabilities in a specialised care environment (replace parents with staff).

Similar sorts of response-reaction cycles seem to occur in colic and Groopman’s article recounts how for even the youngest babies, social relationships are of prime importance.

Link to New Yorker article ‘Colic Conundrum’.

Francis Crick inadvertently raises criminal robot army

Scientific American’s Mind Matters blog covers an interesting study that found that altering people’s belief in free will also altered the likelihood of participants being dishonest in a test of mental ability.

To achieve this, the study used part of Francis Crick’s book The Astonishing Hypothesis that argues against the everyday concept of free will on the basis of neurobiology.

Half of the participants got a passage saying that there is no such thing as free will. The passage begins as follows: “‘You,’ your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. Who you are is nothing but a pack of neurons.”

The passage then goes on to talk about the neural basis of decisions and claims that ‚Äú…although we appear to have free will, in fact, our choices have already been predetermined for us and we cannot change that.‚Äù The other participants got a passage that was similarly scientific-sounding, but it was about the importance of studying consciousness, with no mention of free will.

After reading the passages, all participants completed a survey on their belief in free will. Then comes the inspired part of the experiment. Participants were told to complete 20 arithmetic problems that would appear on the computer screen. But they were also told that when the question appeared, they needed to press the space bar, otherwise a computer glitch would make the answer appear on the screen, too. The participants were told that no one would know whether they pushed the space bar, but they were asked not to cheat.

The results were clear: those who read the anti-free will text cheated more often! (That is, they pressed the space bar less often than the other participants.) Moreover, the researchers found that the amount a participant cheated correlated with the extent to which they rejected free will in their survey responses.

I wonder how specific this is to a general belief in us lacking free will, or whether it’s more specifically to do with a similar belief but which is particularly tied up with the mechanistic concept that Crick discusses – i.e. we’re all just the function of lots of little parts.

The reason I’m wondering this is because the twelve-step approach to addiction recovery has two free-will reducing principles at its core – namely an admission that you are not in control of your addiction and the belief that you have to give yourself up to a ‘higher power’.

The Mind Matters article goes on to discuss the various interpretations of the study and how it fits with our understanding of the philosophy of free will.

Link to Mind Matters on ‘Free Will vs. the Programmed Brain’ (via fc).
pdf of full text of study.

Placebo – interactive ingredients

BBC Radio 4 has just broadcast the first part of a fantastic two part series on placebo, the most effective evidence-based treatment known to science.

It’s written and presented by Bad Science’s Ben Goldacre and is a wonderful trip through the history and science of what we know about this most psychological of treatments.

One of the most interesting recent placebo findings has been that children show a greater placebo response than adults as demonstrated in a systematic analysis of epilepsy treatment trials.

This matches up with the fact that children and generally more hypnotically suggestible than adults.

Various studies in the 1960s and 70s tracked hypnotisability through childhood and found that susceptibility to suggestion varies as a function of age. This summary is from p120 of the excellent academic book The Highly Hypnotizable Person:

Around the age of 7 children show measurable hypnotic ability, which appear to increase until around the age of 12, where it seems to peak. If then appears to plateau for about two years, decreases moderately during adolescence, and then remains stable during early and middle adulthood.

While both placebo and hypnotisability involve the general concept of ‘suggestion’ it’s not been clear whether they reflect the same things at work.

However, recent work by psychologist Amir Raz has suggesting that both hypnosis and placebo may both work through the manipulation of attention, essentially influencing the focus of processing within the brain to alter how it regulates the body and mind.

Link to Placebo programme webpage and audio archive.
Link to full text of placebo in children paper.
Link to Amir Raz paper on placebo, hypnotizability and attention.

Judging trustworthiness in the face

The Boston Globe has a fantastic article on the psychology of trustworthiness judgements and how they can be taken advantage of by con-men.

The article explores studies which have looked at various influences on our judgements of trust. One of the most interesting parts is where they cover research that has systematically altered pictures until the researchers generated faces that seem the least trustworthy (picture of the left) and most trustworthy (picture of the right).

According to recent work by Nikolaas Oosterhof and Alexander Todorov of Princeton’s psychology department, we form our first opinions of someone’s trustworthiness through a quick physiognomic snapshot. By studying people’s reactions to a range of artificially-generated faces, Oosterhof and Todorov were able to identify a set of features that seemed to engender trust. Working from those findings, they were able to create a continuum: faces with high inner eyebrows and pronounced cheekbones struck people as trustworthy, faces with low inner eyebrows and shallow cheekbones untrustworthy.

In a paper [pdf] published in June, they suggested that our unconscious bias is a byproduct of more adaptive instincts: the features that make a face strike us as trustworthy, if exaggerated, make a face look happy – with arching inner eyebrows and upturned mouths – and an exaggerated “untrustworthy” face looks angry – with a furrowed brow and frown. In this argument, people with “trustworthy” faces simply have, by the luck of the genetic draw, faces that look a little more cheerful to us.

Just as in other cognitive shorthands, we make these judgments quickly and unconsciously – and as a result, Oosterhof and Todorov point out, we can severely and immediately misjudge people. In reality, of course, cheekbone shape and eyebrow arc have no relationship with honesty.

There’s plenty more fascinating studies discussed in the article, including an amazing study found that people are more likely to take the advice of someone who has bought the same volume of paint as them compared with someone who buys a different volume of paint!

Link to Boston Globe article ‘Confidence game’.
pdf of study of facial structure and trustworthiness.

The best jobs in life are free

The BPS Research Digest covers a recent study finding that volunteers are actually more committed than paid staff in an organisation, in line with studies showing that payment tends to reduce people’s productivity and enjoyment for the same work compared to when it’s done for free.

A recent study published in the Quarterly Journal of Economics tested this by asking students to complete ‘IQ test’ style questions for varying amounts of money, or by ‘incentivising’ some students on a charity collection day while others collected for free.

In this paper we have provided quantitatively precise evidence, in a controlled environment, of the effect of the introduction of monetary compensation on performance, which includes a precise comparison of the cases in which the reward was given in different quantities or not given at all. The result has been that the usual prediction of higher performance with higher compensation, when one is offered, has been confirmed: but the performance may be lower because of the introduction of the compensation.

In other words, those who were paid more worked harder than those who were paid less, but the hardest work was done by those not paid anything at all.

Link to BPSRD on the commitment of volunteers.
Link to summary of payment and productivity paper.
pdf of full-text.

Neurowar report online

After some exploring of links, the ‘neurowar’ report we mentioned the other day is freely available online, albeit in a non-portable format that doesn’t seem to be displayed very reliably.

Some pages don’t seem to load and I assumed this was to restrict the online version but it turns out it’s just a bit badly set up. However, with a bit of patience and a few page reloads it’s quite readable.

The report makes links between emerging areas of cognitive science and the ‘Potential Intelligence and Military Applications of Cognitive Neuroscience and Related Technologies’.

If you want a slightly briefer summary, a pdf of the executive summary is also available online.

Why they just can’t release the whole thing as a PDF is still, however, a mystery.

Or just in pill form. They can do that, can’t they?

Link to online report.
pdf of executive summary.

Encephalon 52 raises its hand

The 52nd edition of the Encephalon psychology and neuroscience writing carnival has just arrived, this time hosted by the excellent Ouroboros.

A couple of my favourites include a post on the latest science of ‘grandmother cells‘ at the combining cognits blog (the new name for the excellent ‘Memoirs of a Postgrad’) and another on neuroimaging and social attachment style on the new-to-me but engaging Neurotic Physiology.

There’s plenty more article in this fortnight’s edition, so have a look and see what sparks your curiosity.

Link to Encephalon 52.

Tweaking with Sherlock Holmes

I just found this fascinating aside on Sherlock Holmes in a 1973 paper on amphetamine psychosis, suggesting that the cocaine-using Holmes displayed the classic repetitive behaviour often seen in frequent users of dopamine-acting stimulants.

The paper discusses what was known about the pharmacology of amphetamine in the early 1970s and how it relates to psychosis, but starts with an excellent description of the effects of chronic speed use.

One of these constellations involves an intense feeling of curiosity, often manifested by repetitious, stereotyped examining, searching, and sorting behaviors. This repetitious activity has been variously called “punding”, “hung-up activity”, “obsessive-compulsive tendencies”, and “knick-knacking” (by inhabitants of the Haight-Ashbury scene).

Its characteristic feature is engagement in tasks that primarily involve small bits or minutiae and a marked enhancement of perceptual acuity directed toward these minute objects. At times there are perceptuo-motor compulsions, manifested as repetitious stringing of beads or as acts of arranging, sorting, and lining up pebbles, rocks, or other small objects. Most of the so-called “speed art” is replete with complicated syntheses of a multitude of minute details, often depicting universal themes or mandalas. Speed users are frequently observed taking apart such objects as television sets, watches, radios, and phonographs.

Subsequently, the parts may be analyzed, arranged, sorted, filed, and cataloged and, rarely, put back together. Many patients report a sense of satisfaction associated with this compulsive-like conduct. Perhaps the best-known example of searching and examining behavior is that of Sherlock Holmes, whose cocaine habit was described by Dr. Watson:

Finally he thrust the sharp point home, pressed down the tiny piston, and sank back into the velvet-lined arm-chair with a long sigh of satisfaction. Three times a day for many months I had witnessed this performance…

‚ÄúIt is cocaine,‚Äù he [Holmes] said, ‚Äúa seven-per-cent solution… I suppose that its influence is physically a bad one. I find it, however, so transcendently stimulating and clarifying to the mind that its secondary action is a matter of small moment…

‚ÄúMy mind,‚Äù he said, ‚Äúrebels at stagnation. Give me problems, give me work, give me the most abstruse cryptogram, or the most intricate analysis, and I am in my own proper atmosphere. I can dispense then with artificial stimulants. But I abhor the dull routine of existence. I crave for mental exaltation. That is why I have chosen my own particular profession, or rather created it, for I am the only one in the world…

“To the trained eye there is as much difference between the black ash of a Trichinopoly and the white fluff of a bird’s-eye as there is between a cabbage and a potato.” “You have an extraordinary genius for minutiae,” I [Watson] remarked (The Sign of the Four, pp. 610-612).

Holmes’s description of his “grooving on” puzzles and cryptograms and his penchant for magnificent synthesis of details to solve a given case are quite analogous to the amphetamine addict’s intense curiosity and preoccupation with minutiae. Even at a low point in the drug-use cycle, these persons will seek out stimulating mechanical or intellectual puzzles. This compulsion for analysis is widely recognized in the “speed scene.”

Of course, cocaine wasn’t the only drug Holmes dabbled in, as he was also a user of opium and tabacco, but it’s interesting that the author of the paper makes a link between Holmes’ cocaine use, and both his investigative style and ‘knick-knacking’ between cases.

Link to full text of paper.
Link to PubMed entry.

Psycho killer – Qu’est-ce que c’est?

Bad Science has an excellent article about the almost unreported news that homicides by people with mental illness have dropped dramatically in England and Wales, despite the fact that murders by people without mental illness have increased.

Right now I’m looking at a press release on a story which seems pretty important to me: people with serious mental illnesses are committing fewer murders than ever before, by a truly enormous margin. Homicides in this group increased from around 40 a year in the 1950s to 100 a year in the 1970s, in line with a similar increase in the general population. But while murders by people like you have continued to increase, and roughly trebled (0.6 per 100,000 of population in the 1950s, and almost 2 per 100,000 now), murders by people with serious mental illnesses, despite the hype and the fear, the public pronouncements and the headlines, have come down massively since the 1970s, to fewer than 20 a year today.

Ben laments the fact that even a hint of a connection between mental illness and murder makes front page news, stigmatising those with mental disorders and unnecessarily increasing prejudice, while news based on thorough research showing that these fears are unreasonable and unfounded barely raises a byline.

Indeed, it’s rare that positive mental illness news is made ‘sexy’ by the media. The nearest we get is when celebrities admit that they’ve suffered depression. Eating and anxiety disorders are occasionally discussed but it’s rare that psychosis is ever discussed in terms of recovery and by celebrities who have experienced it.

By the way, the picture is of bluesman and ex-Fleetwood Mac guitarist Peter Green who spent some tough years in psychiatric hospital, apparently diagnosed with schizophrenia, but is still as rock n’ roll as ever – recording and touring with some of his best material.

Link to Bad Science on ‘The news you didn‚Äôt read’.
Link to full-text of study.

Neurowar of words

Wired Science covers a recent US military report on military threats from the latest developments in neuroscience as well as how brain research could be ‘weaponised’ to enhance soldiers’ capabilities or disable enemy fighters.

It’s a bit difficult to judge the quality of the report, as unlike the recent in-depth report from the JASON Pentagon advisory panel, they’re charging people to download it.

From the Wired summary, it seems to cover similar ground although is perhaps a little more wide-ranging and focuses on policy and foresight rather than the nuts and bolts of brain science.

It apparently covers four main areas: mind reading; cognitive enhancement; mind control and brain-machine interfaces. As you can probably tell from the list, there’s likely to be a fair amount of speculation going on there.

It’s also interesting that the US military are really promoting their ‘military neuroscience’ angle, which is not to say that it is not a research priority. Whole wings of military research are now devoted to ‘human research’, as illustrated by the extensive science portfolio of the US Army’s Research Lab.

Nevertheless, the discussions about drug-based enhancements have so far been largely reiterating what soldiers have already done for millennia – using drugs to reduce fatigue, increase confidence and cope with trauma.

Drugs have been used for soldiering as long as there have been wars and the low-tech still prevails – from the use of coca leaves by Inca warriors to the use of the khat by modern-day Sudanese militias.

If anyone does happen to stumble across an unrestricted copy of the report online, do let me know as it’d be great to be able to link to the original.

Link to Wired Science article ‘Uncle Sam Wants Your Brain’.
Link to online shop for report.

Knitting delusions from thoughts

An insightful excerpt from psychologist Peter Chadwick’s chapter from an excellent new academic book on the science of persecutory delusions. Chadwick is a clinical psychologist and leading psychosis researcher who has experienced madness first hand.

When looking at Hopper’s forlorn paintings one has the feeling that no moment in life need be wasted. Hopper captures a barman putting a glass or cup on a shelf; a women looking at her nails, another woman lost in thought in a cafe. Little things, things one wouldn’t normally notice or think about, let alone render on canvas, are there to be appreciated.

Some of the experiential moments which built the network of emotionally charged ideas that mediated my own psychosis were trivial in themselves. A remark from my mother; an insult from a bully at school; a strange expression on a shop assistant’s face. But all were eventually collected up, knitted together and turned into a delusional web of thoughts and feelings that in the end drove me to multiple suicide attempts that very nearly succeeded in killing me.

In madness, no moment of one’s existence seems to be wasted; it is if one’s whole life, and the depths of one’s very being in selective perspective, have been made magically clear in their awful and portentous significance. One’s past comes hauntingly back, in a kind of near-death experience while one is physically fully alive. ‘This is what’s it’s all been leading up to!’ I remember often thinking in the blazing hot, mad hot summer of 1979.

Chadwick also wrote a powerful 2006 article that recounted his experience of madness – weaving his insights as a scientifically inclined psychologist and his considerable literary powers into a piece that stands out as unusually powerful amid the typically arid academic literature.

Link to more details on the book.
Link to article ‘Schizophrenia From the Inside’.

2008-08-15 Spike activity

Quick links from the past week in mind and brain news:

Sharp Brains has a thoughtful piece on the hoped-for demise of dementia.

Peter Donnelly gives an excellent TED talk on how juries are fooled by statistics.

Channel N finds an interesting video lecture on the conditioned fear response and combat resilience in the armed forces.

Apparently we’re a ‘Top 100‘ Mental Health and Psychology Blog.

The Frontal Cortex has an interesting summary of a study on basketball pros and the mirror system. A nice complement to a study on ballet dancers and capoeira experts.

Is being gay in your biology? All in the Mind investigates.

The Situationist has an interesting piece on “The Psychology of Barack Obama as the Antichrist”. Cor blimey!

An interesting project to visualise sound to help deaf people interact with sound is covered by BBC News – with video of it in action.

Wired Science picks up on a new study that finds that placebos work better in children.

Cool! Artwork that displays separate images under different lighting conditions – with videos.

Furious Seasons has an excellent investigative piece on the fact that the FDA seem to be validating new psychiatric diagnoses off their own backs.

The most conceptually confused headline of the year? “Nature Or Nurture: Are You Who Your Brain Chemistry Says You Are?” Actually a study on addiction.

Is psychoanalysis equivalent to a spiritual practice? A commonly made link between psychoanalysis and religion is explored rather deftly in an article for The Immanent Frame.

The BPS Research Digest has an interesting piece on disaster psychology and why so many people perish needlessly in emergencies.

More from the Hot Spanish Psychologist. ¬°Vaya chica!

Not Exactly Rocket Science covers a fascinating study showing that referees have a tendency to award more points to competitors wearing red.

YouTribe

Anthropologist Michael Wesch gave a thoughtful and engaging talk on ‘An anthropological introduction to YouTube’ to the Library of Congress earlier this year and, rather appropriately, it’s available online as a video on the popular video sharing site.

Wesh runs a digital ethnography project which looks at how cultures form and operate on the net.

The project’s blog is also full of fascinating insights and is well worth checking out if you thought anthropology was only ever about people who don’t have electricity.

Link to talk ‘An anthropological introduction to YouTube’.

‘Anti-torture’ candidate to run for APA presidency

Despite the American Psychological Association revising their ethics policy twice in the debate over American psychologists’ participation in war-on-terror interrogations, significant unrest still remains over the fact the APA has yet to actually enforce its reluctantly implemented ban.

The Boston Globe has an op-ed article by psychologist and APA critic Stephen Soldz who notes that an anti-torture candidate has been put forward for the APA presidency in an attempt to force the Association’s hand.

The new candidate is psychologist Steven Reisner who even has a campaign website – an innovation for presidential elections which are usually wildly underwhelming.

According to the Globe piece, Reisner received the most votes of the five candidates in the nomination phase. If the momentum carries forward, APA’s careful tiptoeing to avoid offending the US military may backfire if the most political president for years takes the helm.

Interestingly, both Soldz and Reisner are psychoanalysts, a group who have been leading the campaign against psychologists’ role in US military interrogations and who have consistently opposed the ‘war-on-terror’ since it began.

Freud himself was particularly interested in the tension between individual drives and governmental control. In Civilization and its Discontents he suggested government was an inevitable result of the need to control the unacceptable desires we all have.

He was particularly interested in how common individual neuroses get expressed socially as we project our own fears onto specific groups deemed to be ‘outsiders’, often with barbarous and disastrous consequences.

Link to Boston Globe op-ed.

Hypnosis addiction: the scourge of the Victorian lady

I’m currently reading the wonderful but very long book The Discovery of the Unconscious which I shall post more about later.

However, I noticed this little gem about hypnosis in the late 1800s which just smacks of the current hand-wringing over the non-existent (or rather can’t-existent) ‘internet addiction’.

The problems described are so obviously not addiction, and, in fact, like the internet, there’s no specific activity to be addicted to that is defined by the term ‘hypnosis’. After all hypnosis is just where you concentrate and someone makes suggestions – can you be addicted to concentration and listening? Obviously not.

Nevertheless, the concerns got framed in the language of addiction as a placemarker for a fear of the unknown and as a fig leaf for other social problems (from p118):

Deleuze and the early mesmerists also described the evils resulting from too frequent or too prolonged hypnotic sessions. Such subjects gradually became addicted to hypnosis: not only did their need for frequent hypnotization increase, but they became dependent on their particular magnetizer, and this dependency could often take on a sexual slant. This well-known fact was rediscovered by Charcot, who gave an account of a woman who had been hypnotized five times within three weeks and who could think of nothing but her hypnotist, until she ran away from her home to live with him. Her husband took her back, but she fell into severe hysterical disturbances that necessitated her admission to a hospital.

Link to Wikipedia page on The Discovery of the Unconscious.

Interrupting Napoleon on the genetics of mental illness

Today’s Nature has got an interesting letter on psychiatric genetics suggesting an interesting approach to studying the genetics of mental illness.

It’s from neuroscientists John McGrath and Jean-Paul Selten and comments on an earlier Nature article which we discussed previously.

Napoleon Bonaparte advised: “Never interrupt your enemy when he is making a mistake.” Those of us who assess the contribution of non-heritable risk factors to neuropsychiatric illness would like to politely interrupt this battle to remind opponents that environmental risk factors have now overtaken genetic factors with respect to both effect size and the proportion of the population that is affected.

For schizophrenia, for example, factors relating to urban birth, cannabis use and migrant status are well replicated and have relatively large effects ‚Äî in contrast to the scant evidence that remains after decades of genetics research. Although the ‘heritability index’ for schizophrenia is large (about 85%), this metric encompasses the neglected contribution of gene‚Äìenvironment interactions, as well as the high-profile genetic component. This key point is largely forgotten in the heat of the battle.

It has been convincingly argued (A. Caspi and T. E. Moffitt Nature Rev. Neurosci. 7, 583‚Äì590; 2006) that the power to detect genuine genetic-susceptibility loci would be substantially increased if we could stratify samples according to environmental risk factors. Let’s have more funding to help fine-map the wide range of non-heritable risk factors associated with disabling disorders such as schizophrenia and depression, and discover how they act. These clues are too valuable to overlook.

It’s an interesting point and is relevant to the fact that heritability must be one of the most misinterpreted statistics in genetics.

If a study reports that schizophrenia has a heritability of 85%, many people interpret it to mean that 85% of the risk of developing schizophrenia comes from genetics and this is something to do with the condition itself.

In fact, what it shows is that 85% of the risk of schizophrenia in the samples taken so far is estimated to come from genetics, but crucially this estimate is dependent on the environment in quite subtle ways.

The letter above mentions gene-environment interactions: where exactly the same genes can produce different heritability depending on the environment.

Imagine that everyone lived in a virtually identical environment and we all had almost exactly the same life experiences. The only possible difference in the prevalence of mental disorder would have to come from genetics, because the environment is virtually the same for everyone. In this case, heritability would be close to 100%.

Alternatively, if the environment was widely different for everyone, much more of the difference would come from experience and so the heritability estimate would be less.

In other words, the estimate of heritability depends partly on the variability in the environment experienced by the people being studied.

I was told by a genetics researcher that studies on the genetics of intelligence in school children tend to show that IQ is more heritable in the UK than the US, because in the UK we have a National Curriculum – a specified education programme that every child follows.

This means that UK children have a more similar learning environment, whereas in the US the curriculum is decided state-by-state meaning there’s much more variability in experience. Hence, IQ is less heritable in US school children.

I’ve not found the the studies on IQ in school children, so I’m not sure how it stands at the moment, but it serves as a good illustration of how heritability estimates can be environment dependent.

Actually, this week’s Nature has two other letters on the same topic, and additional feature articles on autism and neural synchrony, as well as a couple brain-relevant book reviews.

Link to contents of this week’s Nature.
pdf of Nature Reviews Genetics paper on twin studies and heritability.