Category Archives: genetics

A gene that affects episodic memory?

A tantalizing study, published in Science, indicates that a SNP in a single gene KIBRA, could lead to a difference of as big as 25% in the outcome of a free recall test measuring the episodic memory. The KIBRA gene is expressed in the medial temporal lobe (the hippocampal region) and using fMRI the authors were able to demonstrate different levels of activation in this brain area for the carriers versus non-carriers of the T allele when they were engaged in a retrieval task.

Human memory is a polygenic trait. We performed a genome-wide screen to identify memory-related gene variants. A genomic locus encoding the brain protein KIBRA was significantly associated with memory performance in three independent, cognitively normal cohorts from Switzerland and the United States. Gene expression studies showed that KIBRA was expressed in memory-related brain structures. Functional magnetic resonance imaging detected KIBRA allele–dependent differences in hippocampal activations during memory retrieval. Evidence from these experiments suggests a role for KIBRA in human memory

This is an important work and could lead to much insight on the memory formation mechanisms involved.

Hat Tip: Small Gray Matters

Gender bias in Math skills : a case of Traits Vs. Environment/Effort feedback?

A recent news article reports on a study that demonstrates that the gender bias in Math abilities may be due to environmental and cultural effects – specifically as a result of the negative self- perception garnered by the activation of the negative stereotype of women as having grossly inferior mathematical abilities than men.

The experiment involved giving 220 female study participants bogus scientific explanations for alleged sex differences in math and then having them write math tests. Those who were given a ‘nature’ explanation – that women have differential genetic composition than men and the cause of their low maths abilities was genetic and gender based – performed poorly on the Math tests compared to the group that was told that their math skills depended on how they were raised and were given a ‘nurture’ explanation and an experiential account of the sex differences such as math teachers treating boys preferentially during the first years of math education.

In the control condition some females were told that no sex differences exist while another group was reminded (primed) of the stereotype about female math under-achievement.

The worst performance was for genetic explanation females, followed by ‘stereotype primed’ females. Those who were given an experiential explanation performed as well or better than the control group that received the feedback that there were no sex differences in Math abilities.

While the authors analyze and explain the results in terms of the ‘Stereotype theory’ – that genetic explanations lead to more negative stereotypes and that activation of the negative stereotype affects performance- a more parsimonious explanations is that the differences can be explained by the same differential outcomes that are observed in people who have a genetic or trait-like versus an effort-driven or skill-like view of abilities. I have discussed previously how these differential view of abilities may develop and the experiment above has just the right conditions to induce such a differential view.

Those who were given a genetic explanation of sex differences in math abilities, may have formed a trait-like view of Math ability and were prone to see the ability as stable, genetic and immutable. This is the same view of math ability that would be formed if they had been given generic feedback – like “you are a math prodigy”.

Those who had been given experiential explanations of sex differences would have been more prone to form a skill-like view of math abilities and assume that the ability could be improved and honed based on environmental inputs like proper teaching, guidance, strategy or efforts. This would have been the case if they had been given ‘specific’ feedback – like “you solved this math problem very well this time”.

It is evident that a large part of the difference in the math test results observed in genetic vs experiential explanation conditions can be explained by the different view about math abilities that these experiments had induced. Those who were having the trait-like view of math ability would get frustrated while tackling a difficult problem and would be less resilient and effort-full while tackling the latter, more easy, problem on the test; as they would have formed a negative self-perception as one who has little mathematical talent. On the other hand, those who had been induced to form a skill-like view of math ability, would have been more resilient and effort-full when tackling latter problems, despite some early failures, as a failure would not have led to a resigned sate of mind, but would have only resulted in a belief that the strategies or effort or earlier training had not been sufficient to solve the particular problem.

It is not my contention that negative stereotype activation has no role to play- priming with stereotype words does lead to measurable effects on performance – but in this case, even if the stereotype activation is involved, the stereotype may be instrumental in activating the differential view of mathematical abilities and its effects mediated by the effects that such views have on test performances.

Mouse research: Genetic footprints of anxiety?

A recent study, has determined that a Single Nucleotide Polymorphism (SNP) in the BDNF (Brain deriver neurotopic factor) gene in humans, that substitutes a Met allele for Val, may be a predictor for increased susceptibility to anxiety/ depression. The study involved experiments with mouse homozygous for the Met allele and placing them in stressful situations. These mice exhibited considerable increase in anxiety over normal mouse when facing similar situations. Thus, a potential locus and mechanism for anxiety/ depression has become available.

It is interesting to note that a similar SNP that involves Met/Val substitution in the COMT gene has been implicated in schizophrenia and affects cognitive performance in frontal regions. In the COMT case though, those who have the Met allele are more fortunate, in the sense that the Val allele causes increased metabolism of dopamine and other catecholamines.

While a Met allele is good in a Schizophrenia gene, it has the reverse effect in a depression/anxiety gene! What exactly does the Met / Val difference mean for a gene?

Hat Tip: The Mind Blog

Belief about Intelligence : how it affects performance and how it is formed

Affective Teaching keeps posting some interesting basic cognitive tutorials and their latest one deals with the different concepts people have regarding intelligence and how that affects performance and attitudes.

As per that tutorial, people can either have fixed (entity) or trait-like view of intelligence/ abilities or a changeable (incremental) or skill-like view of intelligence/ abilities. Interestingly, those with fixed view are more prone to learned helplessness, external locus of control, less persistence and lack of use of learning strategies. On the other hand those with changeable view of intelligence are more persistent, having a mastery goal or orientation and apt to use learning strategies and credit success to effort and strategy.

This same difference in attitudes and outcomes was predicted by my recent blog post where I analyzed the differential effects of providing generic (person based) versus specific (outcome based) feedback and praise. It was surmised that this would lead to differential view of intelligence/abilities as being trait-like or skill-like in nature. It is heartening to note that existing research supports such a differentiation in the conceptualization of intelligence by individuals and also predicts accurately the different outcomes based on different underlying conceptualizations.

It should thus be clear that providing the right sort of feedback to the child is very important so that they hook on to the right conceptualization of intelligence early on. This may also go long way in settling the expertise debate: genius have a mastery orientation and an incremental view of intelligence which is different form the normal trait-like view held by most people. Thus, it is not just the case that that they are either more talented or just better learners (although they are both) ; they also have a different attitude- and a different underlying concept of intelligence/ability- which is very much a result of the environmental feedback they received in childhood ans is instrumental in making them what they are.

Is low IQ the cause of income inequality and low life expectancy or is it the other way round?

As per this post from the BPS research digest, Kanazawa of LSE has made a controversial claim that economic inequality is not the cause of low life expectancy, but that both low life expectancy and economic inequality are a result of the low IQ of the poor people. The self-righteous reasoning is that people with low IQ are not able to adapt successfully to the stresses presented by modern civilization and hence perish. He thinks he has data on his side when he claims that IQ is eight times more strongly related to life expectancy, than is socioeconomic status. What he forgets to mention(or deliberately ignores) is growing evidence that IQ is very much determinant on the socioeconomic environment of its full flowering and a low IQ is because of two components- a low genetic IQ of parent plus a stunted growth of IQ/intelligence due to impoverished environment available because of the low socio-economic status of the parents.

A series of studies that I have discussed earlier, clearly indicate that in the absence of good socioeconomic conditions, IQ can be stunted by as large as 20 IQ points. Also discussed there, is the fact that the modern civilization as a whole has been successful in archiving the sate of socioeconomic prosperity that is sufficient for the full flowering of inherent genetic IQ of a child and as such the increments in IQ as we progress in years and achieve more and more prosperity (the Flynn effect) has started to become less prominent. This fact also explains the Kanazawa finding that in ‘uncivilized’ sub-Saharan countries the IQ is not related to life expectancy, but socio-economic status is. although, he puts his own spin on this data, a more parsimonious ( and accurate) reason for this is that in the sub-Saharan countries, even the well -of don’t have the proper socio-economic conditions necessary for the full flowering of IQ and thus the IQ of both the well-off and poor parents in these countries is stunted equally. Thus, the well-off (which are not really that well-off in comparison to their counterparts in the western countries) are not able to be in any more advantageous position (with respect to IQ) than the poor in these countries. The resultant life expectancy effect is thus limited to that directly due to economic inequality and the IQ mediated effect of economic inequality is not visible.

What Kanazawa deduces from the same data and how he chooses to present these findings just goes on to show the self-righteous WASP attitude that many of the economists assume. After reading Freakonomics, and discovering how the authors twist facts and present statistics in a biased manner to push their idiosyncratic theories and agendas, it hardly seems surprising that another economist has resorted to similar dishonest tactics – shocking people by supposedly providing hard data to prove how conventional wisdom is wrong. Surprisingly, his own highlighting of sub-Saharan counties data that shows that life-expectancy is highly dependent on socio-economic conditions in these countries is highly suggestive of the fact that in cultures where the effects og economic inequality are not mediated via the IQ effects, economic inequality is the strongest predictor of low life expectancy.

Instead of just blaming the people for their genes/ stupidity, it would be better to address the reasons that lead to low IQs and when they are tackled, directly address the social inequality problem , as in the author’s own findings, when IQ is not to blame for the low life expectancy, the blame falls squarely on economic inequality (as in the sub-Saharan countries data) .

IQ variations across time and space : the why and wherefore?

Mind Hacks has two posts on IQ: one focusing on IQ variants across time and discussing Flynn effect and the other focusing on variation across space (different population groups!) and discussing variation in IQ of identical and fraternal twins and taking help of adoption studies with special focus on economic background of biological and adopted parents.

I’ll discuss the second posting first which is based on this NYT article.

This article mentions a few observations based on meta analysis of data related to twin studies and also a study of adopted children -raised either in environments (adopted homes) that are of same socio-economic status as that of their biological parents or in different socio-economic environments.

Some of these observations are (first six are from adoption studies and the seventh is from twin studies. :

  1. Children of well-off biological parents reared by poor/well -off adopted parents have Average IQ about 16 point higher than children of poor biological parents
  2. Children of well-off biological parents reared by well-off adopted parents had average IQ scores of 119.6
  3. Children of well-off biological parents reared by poor adopted parents had average IQ scores of 107.5 – 12 points lower
  4. Children of poor biological parents reared by well-off adopted parents had average IQ scores of 103.6
  5. Children of poor biological parents reared by well-off adopted parents had average IQ scores of 92.4
  6. In another study, the average I.Q. scores of youngsters (from an orphanage at ages 4-6)placed in well-to-do homes climbed more than 20 points, to 98 – a jump from borderline retardation to a whisker below average , when measured after 9 years of placement in the well-off home. That is a huge difference – a person with an I.Q. of couldn’t explain the rules of baseball, while an individual with a 98 I.Q. could actually manage a baseball team – and it can only be explained by pointing to variations in family circumstances.
  7. In a meta-analysis, it was found, that among the poorest families , for those twins raised in the poor families, the I.Q.’s of identical twins vary just as much as the I.Q’s of fraternal twins; while in rich families the IQ’s of Identical twins are more identical than is the case for the IQ differences in fraternal twins.

First let us discuss the Twin studies (observation 7). If some trait A is found to co-occur say 80% of the times in identical twins (which have identical genotype) that are raised apart and if the same trait A is only found to vary 40 % of the times in fraternal twins (that have only 50 % of genes in common) that are raised apart; then one can conclude that this trait A is highly heritable and genetics dependent, with environmental influence limited to say affecting only say 20 % variation in the trait.

The premise is that if it is conclusively proved that if two organisms (identical twins) which contain more similar genes (double the number in comparison to fraternal twins) than a control pair of organisms (the fraternal twins); and effect of environment is subtracted (by letting the two organisms live in dissimilar environments – one adopted, while the other in biological home atmosphere); and if it is found that some trait A is found to concur more in these organisms (identical twins) compared to the control pair (the fraternal twins), then that trait must have a genetic component and is heavily influenced by genetic factors as opposed to environmental factors. So far so good.

In the normal twin studies, the adopted twin generally belongs to the same socio-economic status as the one reared by the biological parents.

The normal observation that identical twins belonging to well-off/middle class families have IQ rates similar as compared to fraternal twins, thus indicates that for children from well-off background (biological/adopted), the IQ (observed phenotype) is mostly due to genetic factors (underlying genotype) and environmental factors are not a big determinant.

The paradoxical observation that identical twins belonging to poor families have IQ rates as varying as compared to fraternal twins, should indicate that for children from poor background (biological/adopted), the IQ (observed phenotype) is mostly due to environmental factors and genetic factors (the underlying genotype ) are not a big determinant.

How do we conciliate the two observations. The paradox becomes a non-issue when one shifts focus from either-or thinking in terms of gene-environment influences and moves towards an interactionist view point viz. Nature via nurture as outlined by Matt Riddley amongst others and using genotype-phenotype distinctions. As per this viewpoint, any genotype is a potentiality and only if proper environmental factors are available can it lead to the desired (adaptive) phenotype. In absence of the required environmental factors, the genotype may not lead to the phenotype or may lead to sub-optimal phenotype expression. In a typical example, a fish may not show the color that the genotype codes for, if the environment under which it is developing provides little incentive to exhibit that color for reproductive/survival fitness. In less dramatic example, one may have genotype for having a more than average height, but if proper nutrition during a critical phase of development is not provided, then that height may not be exhibited.

Returning back to our discussion, it is apparent that IQ , though highly heritable ( and being genotype based), remains as a potentiality and only if environmental factors ranging from nutrition to socio-economic factors resulting in environmental influences like number of words exposed during childhood, results in appropriate IQ scores and intelligence (observed phenotype) only when such environmental influences as measured by socio-economic atmosphere during childhood are present during critical stages of development. Thus, while children of and raised by well-off parents could have a high correlation between genotype and phenotype ( and thus show high correlation in IQ across identical twins vis-a-vis fraternal twins), the same would not be true for children of poor parents where environmental factors will limit the observed IQ scores ) and thus, though the genotype of identical twins is similar than fraternal in this case too, the variation would be greater as the genetic influence has been subdued by environmental (negative) influence.

Now to explain the first observation, viz. that children of biological parents have average IQ higher than children of poor/working parents can be explained by the fact, that as a group, the well-off parents would have higher IQ than poor/working parents- as intelligence would be one of the major factors predicting who would be well-off and who would be poor in a fair world. Thus, it is no surprise that their children, would also have higher intelligence as compared to poor children- as the rich parent’s child would on an average get better IQ genes than a poor children would get from its poor (and less IQ) parent.

The observations 2 and 3 taken together corroborate the fact that IQ flowers only under the right environment. When 2 child start with similar average IQ potentialities (as they are from well-off parents), they nevertheless end with different final exhibition of intelligence (as measured by IQ scores) based on the limiting influence of environment on the genes.

The observations 4 and 5 taken together yield to similar interpretations.

The observation 6 is a stark example of how providing a proper environment can lead to drastic improvements in the exhibited phenotype and lead to the phenotype attaining the maximum potentiality present in its genotype.

It is clear that affirmative action is needed to ensure that environmental influences do not lead to sub-optimal flowering of intelligence. These affirmative actions should be based on reducing poverty and focused on that alone. Other options like Mandal commission reservation of jobs (after the child has already got a sub-optimal IQ due to early socio-economic environment) are clearly counter-productive and unfair. Poverty is the only evil to be tackled.

Returning to the first post on Mind Hacks related to Flynn effect,based on this American Scientist article. To me, it seems apparent, that biological evolution is very slow in comparison to social and environmental evolution that we humans have managed to achieve. I believe that based on our current genotypes for intelligence, we have achieved a plateau in terms of providing the maximal socio-economic environmental conditions necessary for full flowering of intelligence. Thus, we seem to be reaching a plateau in terms of increases in IQ score from one generation to the other. The Flynn Effect, in my opinion, was not a change in genotype, but in exhibited phenotypes, due to availability of proper environmental conditions.

For IQ to change within generations due to underlying change in genotype is assuming heavy and continuous selection pressure on those genes responsible for IQ. I believe that IQ (and intelligence) would keep on improving, as it may be part of runaway selection due to other-sex mate preference (reproductive advantage) – like that of evolution of beauty – or peacock’s tail – or it may keep evolving as intelligence does confer survival advantage too, but such increases would not be as dramatically observable as the Flynn effect.