Friday, January 6, 2012

Nature and Nurture Fistfight on Campus

The issue of whether our genes determine our abilities, our desires, our choices,or our future GPAs rears its (ugly?) head from time to time.  I have no background in psychology, neurobiology or development.  But my particular subfield of Hamster Husbandry involves understanding the inheritance of desirable fur qualities, so I have some grounding in the basics of genetics and statistics that also underlie the research on genetics of scholastic performance (or IQ, 'g', SAT scores etc).  I occasionally have to touch on it in class, so I looked into the research a couple of years ago, and since it popped up again recently, I thought I'd offer a summary in case it's helpful.

There is almost no trait that is entirely genetic or entirely environmental (to geneticists 'environmental' simply means not genetic).  Even the classical genetic disorders are often amenable to treatment by altering some aspect of the environment (diet or drug therapy).  On the other hand all of our cognition takes place in our brain - a biological organ built of membranes and enzymes. The structure of those enzymes is coded in genes, along with much of the information as to the circumstances under which those enzymes are produced or the cells connect one way or another. 

The key phrase is 'under what circumstances'.  Even the structure of the brain is partly influenced by its responses to external stimuli (the environment).  This is what is meant by phrases like 'the brain changes itself', and is the same basic principle as our muscles changing in response to exercise, or our plants getting larger when we water them - responding to environment cues and stimuli is part of the development of all living things.

So the argument is over how much our differing abilities and preferences is attributable to our different genetic backgrounds or our different environments.  Do parents and offspring have similar levels of success because the offspring inherit genes or because they inherit environmental advantages?  Is education and social environment just fiddling around the edges of a genetically determined core, or do we all start out essentially the same, and diverge as our experiences shape us?  I believe the latter is much closer to the truth, but this is getting lengthy, and I've finally learned to use jump breaks (see, and environmental effect!) so I'll continue after the jump.

Twin studies claim to show a strong genetic effect, but have a serious flaw.  Twin studies assume that since the genes of twins are the same, the more that twins who have been raised apart are similar cognitively, the greater must be the effects of the genes.  But to be valid the twins have to be not just reared apart, but to be raised in completely random environments (imagine picking two households at random from across the entire US and plopping one twin into each).  Of course this isn't what was done.  So the studies might show that twin males raised in the 1950's in rural Arkansas differ in some consistent way from twin girls who grew up in 1980's San Francisco.  This is hardly strong evidence for genetic control of our minds.  I'm quoting the older Minnesota Twin Study - recent studies are somewhat better, but none can eliminate the common uterine environment of twins.

Environmental influences do not mean a trait is infinitely maleable.  An old, if minor, hand injury means that I would have to work a lot harder to be a great concert pianist than if the injury hadn't happened.  And I could probably never be 'the best' starting from a disadvantage.  This strikes me as particularly relevant to early childhood development (in which I have no expertise) where early differences in some aspect of the child's environment could become amplified in their scholastic achievement later on.

By the same reasoning, some improvement is almost always possible.  Neither genetic, nor earlier environmental influences on scholastic achievement are locked in and impervious to improvement.  My hand injury doesn't mean I won't getter at piano if I practice.  Your houseplant may never grow into a oak, but it will still get bigger if you water it, and wither if you don't.  That sounds cheesey, but one hears the argument made sometimes that 'that's just the way they are', and the argument is false.

Alleged racial differences are seriously confounded, because whatever genetic difference might exist is correlated with different environments.  So if there is a tendency for one group to score higher or lower, this cannot be automatically attributed to 'innate' genetic differences.  (The same goes, mutatis mutandis for gender.)  It is virtually impossible to put different ethnic groups into the same 'environment' for a fair comparison, because of the vastly different experience of being white or black or hispanic or asian in our society, even when attending the same school or having the same 'socio-economic status'.  What is clear is that when (some of) these factors are taken into account (the statistical technique, ANCOVA, is well established) the differences between races shrink close to zero.   (A rough analogy might be to say that of all the variation among the performance of different computers, only a small fraction can be predicted by the hardware difference between Mac's and PC's - the rest being different software, roughly analogous to the educational environment of a person.   I can't help noticing that the Mac vs PC partisans can be almost comically tribal as well).

The trouble with any 'predictor' of future scholastic performance is that they are statistical, and probabilistic.  They can only predict (often very small) differences in the likelihood of a particular outcome.  This only manifests itself as trends over large groups, which is inevitably unfair to particular individuals.  I suspect this is as true of reference letters as it is of SAT scores, but I couldn't prove it.

 Sorry for the longwinded post.  I hope it is helpful.  I found a useful quote from Dennett that might sum it up.

Once the caricatures have been set aside, what remains are honest differences of opinion about how much intervention would be required to counteract one genetic tendency* or another and more important, whether such intervention would be justified.  These are important moral and political issues, but the often become next to impossible to discuss in a calm and reasonable way.

*I would just add that the same goes for dealing with tendencies induced by past environmental experiences.


  1. I like the Dennett quote, much more so with your addition. And the "more important" question it raises is, indeed, the question we should be dealing with.

    There are significant performance differences linked to both race/culture and SES (and gender). Now what? How can educators at all levels use this information to benefit students?

    And what language can be used so that the ideas survive the political process?

  2. Thank you for taking the time to explain this issue further, we appreciate it.

  3. I am doing some work in this area with a neuro-scientist. Whether genetics or environment, it is clear that certain deficiencies (as measured by the ACT and SAT) appear to be hard-to-impossible to correct once a student reaches higher education.

    I am at an open admission State university, and our long-term graduation rate (independent of major) is perfectly correlated with ACT math score.

    Despite years of effort in remediation (and even trying to water down the curriculum), this does not change. You may call it 'only' probabilistic, but it doesn't alter reality.

  4. Thank you for this; this is a fair critique and highlights the issues I was discussing much more eloquently than I was doing in the other post.

    You do highlight a student selection issue I find compelling - one way to mitigate the racial differences created by using SAT scores is to add SES, cultural heritage, etc. to your prediction battery. Some schools do soemthing like this already (e.g. adding "bonus points" to index scores for attending an inner-city or very rural high school). But I have a feeling that the public reaction to anything larger-scale would be quite negative.

  5. Ricardus, I believe that awarding "bonus" points is the way many colleges practice affirmative action without quotas. In one respect, it does address the problem of certain groups being underrepresented. However, it does harm to those students who received the bonus points.

    College grading is based on merit. I don't know their background. All I know is that a student struggles with algebra in a calculus based chemistry course. Maybe he doesn't study, maybe life's cards were stacked against him. It doesn't matter - the student fails the exam. That same student should have entered a college that was more in tune with his limited abilities, regardless of his background.

  6. And the harm can be significant. Law schools wanting more diversity accept a certain number of students whose LSAT scores are lower than the average for that school. The students go into debt and graduate, but cannot pass the bar exam and enter the profession. The problem of low pass rates for minorities was being discussed 20 years ago and, judging from the percentage of minorities who are members of the bar (the bar is 80% white in my state), it's still a problem. It's no favor to these students to accept them when their chances of ever being able to work in the field they're training for are poor.

  7. @Ricardus & Beaker Ben- Texas tried the "bonus point system" (sort of) in response to the Hopwood decision in the early nineties. The "sort of" was the establishment of the Top 10% Rule that essentially states any student that graduates in the top 10% of a Texas high school class is guaranteed admission to any state school in Texas. (The University of Texas has lobbied to get their admission percentage lowered to 8% because they were getting too many applicants.)

    What began to occur in response was termed "reverse white flight" where families would move their kids out of "competitive" high schools if they were below the top 10% going into their senior year and into nearby "less competitive" schools in order to hit that 10% bar.

    What do you suppose happened to the previously-top-10%ers that got bumped down at the less competitive schools? Yeah. Over time the effect has begun to wear off. School districts have tried to fight back but, low and behold, the parents that do this also tend to have a certain amount of clout in the community.

  8. What I've read on science blogs is that this very question is flawed. I'm no scientist, but supposedly it isn't Nature VERSUS Nurture, but rather Nurture BECOMES Nature. So boys play with dinosaurs and guns and grow up to find violence to be a natural extension of play, while girls play with babies and dress-up and find as adults to feel "natural" -- depending on early development and application.

    (just as similarly, doing the gender norm can feel "unnatural" depending on experiences)

  9. @ Ben. I completely agree. When I suggest that ther is always some possibility of improvement in a salubrious environment, I didn't mean to suggest that simply plopping an unprepared student into a college class qualifies.

    Indeed, as Paddington points out, some past effects (whether genetic or environmental) can be so hard to overcome as to *effectively* preclude ever reaching a particular level for all practical purposes. To extend my injured hand analogy, if the hand had been completely severed, it would be effectively impossible for me ever to be a top piano player barring some medical miracle. (Forgive me if i cavill - it is only because there are lots of conditions that used to be 'impossible' to fix, that are now treatable). By the way, I'm curious, Paddington - are the conditions you refer to major ones (such as fetal alcohol syndrome), or lesser issues of childhood opportunity? Not being involved with the research, I'd be interested to get a better feel for it.

    I must say, though, that I do tend to take any claim of a 'perfect' correlation with skepticism. I notice you say a correlation with graduation *rate*. Since individuals can't have a rate - they either graduate or they don't - I assume this means that some students with low entrance scores do indeed graduate, and some with higher scores do indeed flame out. This is exactly what I meant when I said the prediction is probabilistic for any individual. You can say the former student is less likely to graduate than the latter. But you can't say for sure whether either one will or won't graduate.

  10. @Academic Monkey - I find that slogans like "nature vs nurture" or "nature via nurture" or "nature vs nurture is dead!" are catchy, but that it is too easy to project onto them what we want them to mean. That's why I went to some lengths to try and unpack the issues involved, and I never did set it up as an either-or proposition. (I really only mentioned nature and nurture because it made for a snappier headline than "Some observations on issues related to the relative contributions of genetic and environmental factors to human zzzzzz.....")

    What I think the phrase "nurture becomes nature" (or Matt Ridley's "Nature via Nurture" - another snappy title) describes is the process I described in the 3rd para of my post. The response of the developing brain to external stimuli. What you seem to be describing in your comment (and forgive me if I am misreading you) is more like strict environmental or cultural determinism, for which I gather there is little evidence. The difference between the two is that the former admits the possibility that individuals with different genes might respond differently to the same stimulus.

  11. @Academic Monkey – my hypothesis is that there is a crucial window (somewhere in the age range 11-15) in which a child learns the abstract thought processes. This is known to be true, but at a younger age, for learning speech. It’s why I take such care training future Middle School teachers.

    @Rosenkrantz and/or Guildenstern – you are correct that this does not refer to individuals. However, if you look at the math ACT score only, the 6-year graduation rate is over 80% for 28+, and somewhere around 15% for the 15-17 range (the figures are in my office). As with most of higher education, about 70-80% of our students test into a course around the high school Algebra I level (or a lot lower). No matter what remediation we try, it doesn’t help in any significant numbers. Those students then drop out, saddled with $20,000-$60,000 in debt. Lest you wish to blame mathematics, those who can’t pass the math courses fail almost everything else. I am all for giving a chance, but they should be aware of the odds against them.

  12. @R&G: To extend my injured hand analogy, if the hand had been completely severed, it would be effectively impossible for me ever to be a top piano player barring some medical miracle.

    Point of information: Paul Wittgenstein more-or-less successfully continued his career as a concert pianist after losing his arm in the first world war. But he already had the skills, and just found ways to compensate for the loss of his right arm.

    The problem is that too many students enter college without the necessary skills -- which are what seems to be measured by the ACT, and why the graduation rate for students with low ACT scores is so low.

    In the sciences, at my SLAC, our experience is that students with less than a 21 ACT composite score will almost certainly not succeed, meaning that they will drop below a C-minus in the major before they finish their sophomore year. We've had majors with 18s and 19s matriculate, but they never graduate in the discipline. (Almost never? I can't think of any examples offhand.)

    And I'm glad the Beaker brought up the "bonus point" problem. I've heard that American non-Asian minority students tend to be admitted to schools about one level above their aptitude; this would explain why the trend is for such students to have lower graduation rates.

  13. Cognition is not limited to brain only.

  14. Sawyer, I thought Texas parents moved their kids for football.

  15. Would it be fair then to say that the consensus view goes something like this: A well designed test (what qualifies as well designed being a debate for elsewhere) can do a good job of predicting how likely students are to succeed in college. We can say that students who score X on the ABC test have a 50% chance of graduating. But we can't say which 50% are going to actually graduate and which won't, and this still seems to be a sticking point. We all seem to agree that it is unfair to take a student's tuition money when we have good reason to believe they are unprepared and unlikely to succeed. And we seem agree that some abilities can be brought up to college level much more easily than others. This clashes somewhat with the "believe-in-the-power-of-your-dreams" zeitgeist, and inspiring stories like Wittgenstein's.

    The reason I keep bringing up the probabilistic nature of these predictions is not to disparage them - it is simply the nature of statistical prediction whether we are predicting the chances of college success or the chance of rain next Tuesday. The point is this: If students who score X on the ABC test have a 50% chance of success and are admitted to college, while students who score Y have only a 40% chance and are not admitted, then the second group are entirely justified in feeling a little put out about it. While some of them are genuinely unprepared for college, some of them are probably just lousy at multiple choice tests. And we can't tell which are which.

    So for predicting the chances of success in college admissions (by whatever method, test scores, recommendations, Ouija boards), I think there is an inevitable dilemma. If we lower the acceptance threshold, it isn't really fair to those students who are unprepared, but if we raise it, we deny some students who could catch up the chance to do so. I don't have an answer to this, but maybe it focuses the issue.


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