The fluidity of fluid intelligence

If IQ is a measure of some aspects of intelligence, and intelligence is the product of a gene or genes, then it should follow that IQ is a stable trait during an individual's lifetime. So I was interested to hear on a recent episode of the BBC radio program, Analysis, that IQ can change even over the course of participation in a brief psychological study.

Princeton professor of psychology and public affairs, Eldar Shafir, co-author of the book, with economist Sendhil Mullainathan, "Scarcity: Why Having Too Little Means So Much", was interviewed  on the program about how having too little time or money influences our lives.  Mullainathan and Shafir believe that experiencing scarcity changes the way we think, and makes a bad situation even worse; poverty creates a "scarcity mind-set" and causes poor people to make bad decisions, which perpetuates their poverty.

To test this, they interviewed people shopping in a mall in New Jersey, determined their financial status, presented them with various financial scenarios and then asked them to play computer games that measured their 'fluid intelligence', a component of IQ that indicates things like the ability to think logically, to reason, or to handle novel situations.

When the scenario is manageable, if for example they are asked what they would do if their car breaks down but it won't cost much to fix, poor and rich people perform equally well on the tests.  But if the scenario is challenging, say fixing the car costs $1500, rich people did as well on the intelligence tests as they did before, but poor people did significantly worse.

Mullainathan and Shafir contribute this to scarcity of what they call 'bandwidth', or the amount of mental capacity that is used to make decisions.  They found that IQ fell by 13 points in their poor study subjects given a challenging scenario.  This, Shafir said, can be equivalent to a drop from borderline gifted to average, or average to borderline deficient.  Shafir contrasted this with a night without sleep, which leads the IQ of the sleep-deprived to be 10 points lower than usual.

Scarcity has other effects as well, according to Mullainathan and Shafir, leading people into a cognitive 'tunnel' so that they can't think broadly about how to solve a problem.  Shafir describes it this way in an interview with the the American Psychological Association:

Every psychologist understands that we have very limited cognitive space and bandwidth. When you focus heavily on one thing, there is just less mind to devote to other things. We call it tunneling — as you devote more and more to dealing with scarcity you have less and less for other things in your life, some of which are very important for dealing with scarcity. There's a lot of literature showing that poor people don't do as well in many areas of their lives. They are often less attentive parents than those who have more money, they're worse at adhering to their medication than the rich, and even poor farmers weed their fields less well than those who are less poor.

Clearly this can become politically volatile very quickly; right-wingers might interpret these results as indicating that poor people doom themselves to poverty, while left-wingers interpret them to show that poverty begets poverty.

But it's the effect on IQ that interests me, and yes, this is another subject that gets volatile very fast. How can this thing, that so many believe is genetic and therefore relatively fixed, change so readily, and in fact predictably?  This is not the first time that fluid intelligence has been shown to be, well, fluid.  A 2007 paper in PNAS showed that it is trainable, and can be significantly improved, e.g., and methods for improving intelligence, something previously thought to be impossible, are now rife.

If true, this doesn't mean that genes have nothing to do with intelligence -- whatever that is -- though it does mean intelligence isn't fixed.  Perhaps intelligence can be thought of as analogous to blood lipid levels, say; we may be genetically predisposed to high or low cholesterol, but we can raise or lower our levels with diet, exercise, or medication.  That is, as every trait, it has a genetic scaffolding, but it is also influenced by experience.  And, as with intelligence, some people have extreme cholesterol levels, generally due to single or few genes.  However, generally, these are genes that don't influence cholesterol levels in people between the extremes.

This is of course one implication of the clear fact that the 'heritability' of intelligence is well below 1.0, meaning that environmental factors are important as well as genetic ones.  The volatility of the measure is, however, an indicator that even the trait itself may not be very stable and that 'environment' may not refer just to random non-genetic factors but ones that systematically affect the measure.  In this case, the environmental factor could suggest that people in poverty are poor because of low-IQ genotypes, but Mullainathan and Shafir believe it's more complicated than that, that poverty creates a mindset that perpetuates poverty.

Similar kinds of issues apply to most complex traits.  Heritability can vary with age as well as many other factors, because the impact of environmental factors can change, and perhaps for genetic reasons as well.  Some genetic factors may be expressed differently at different ages.  A major issue in general in regard to complex traits would be if the genetic component doesn't just fix a certain fraction of the trait value, but is volatile.  Then the time and way of measurement could generate values that are taken as more inherent and permanent, but in fact are more widely variable.  The variation could be such that the genetic component is far less relevant than is often thought.  Of course it could be the other way round.  In each trait if we are determined to identify how much is inborn and how much acquired, it may be that we need to be much more knowledgeable about the determinants, and more careful in how we measure traits -- or how we 'label' individuals.