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help explain the way in sports we develop the ability to respond to the rapid- fi re unfolding of events faster than we’re able to think them through, the way a musician’s fi nger movements can outpace his conscious thoughts, or the way a chess player can learn to foresee the countless possible moves and implications presented by different confi gurations of the board.
Most of us display the same talent when we type.
Another fundamental sign of the brain’s enduring mutability is the discovery that the hippocampus, where we consolidate learning and memory, is able to generate new neurons throughout life. This phenomenon, called neurogenesis, is thought to play a central role in the brain’s ability to recover from physical injury and in humans’ lifelong ability to learn. The relationship of neurogenesis to learning and memory is a new fi eld of inquiry, but already scientists have shown that the activity of associative learning (that is, of learning and remembering the relationship between unrelated items, such as names and faces) stimulates an increase in the creation of new neurons in the hippocampus. This rise in neurogenesis starts before the new learning activity is undertaken, suggesting the brain’s intention to learn, and continues for a period after the learning activity, suggesting that neurogenesis plays a role in the consolidation of memory and the benefi cial effects that spaced and effortful retrieval practice have on long- term retention.9
Of course, learning and memory are neural pro cesses. The fact that retrieval practice, spacing, rehearsal, rule learning, and the construction of mental models improve learning and memory is evidence of neuroplasticity and is consistent with scientists’ understanding of memory consolidation as an agent for increasing and strengthening the neural pathways by which one is later able to retrieve and apply learning. In the words
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of Ann and Richard Barnet, human intellectual development is “a lifelong dialogue between inherited tendencies and our life history.”10 The nature of that dialogue is the central question we explore in the rest of this chapter.
Is IQ Mutable?
IQ is a product of genes and environment. Compare it to height: it’s mostly inherited, but over the de cades as nutrition has improved, subsequent generations have grown taller.
Likewise, IQs in every industrialized part of the world have shown a sustained rise since the start of standardized sampling in 1932, a phenomenon called the Flynn effect after the po liti cal scientist who fi rst brought it to wide attention.11 In the United States, the average IQ has risen eigh teen points in the last sixty years. For any given age group, an IQ of 100
is the mean score of those taking the IQ tests, so the increase means that having an IQ of 100 today is the intelligence equivalent of those with an IQ 60 years ago of 118. It’s the mean that has risen, and there are several theories why this is so, the principal one being that schools, culture (e.g., tele vision), and nutrition have changed substantially in ways that affect people’s verbal and math abilities as mea sured by the subtests that make up the IQ test.
Richard Nisbett, in his book Intelligence and How to Get It, discusses the pervasiveness of stimuli in modern society that didn’t exist years ago, offering as one simple example a puzzle maze McDonald’s included in its Happy Meals a few years ago that was more diffi cult than the mazes included in an IQ test for gifted children.12 Nisbett also writes about “environmental multipliers,” suggesting that a tall kid who goes out for basketball develops a profi ciency in the sport that a shorter kid with the same aptitudes won’t develop, just as a
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curious kid who goes for learning gets smarter than the equally bright but incurious kid who doesn’t. The options for learning have expanded exponentially. It may be a very small ge ne tic difference that makes one kid more curious than another, but the effect is multiplied in an environment where curiosity is easily piqued and readily satisfi ed.
Another environmental factor that shapes IQ is socioeconomic status and the increased stimulation and nurturing that are more generally available in families who have more resources and education. On average, children from affl uent families test higher for IQ than children from impoverished families, and children from impoverished families who are adopted into affl uent families score higher on IQ tests than those who are not, regardless of whether the birth parents were of high or low socioeconomic status.
The ability to raise IQ is fraught with controversy and the subject of countless studies refl ecting wide disparities of scientifi c rigor. A comprehensive review published in 2013 of the extant research into raising intelligence in young children sheds helpful light on the issue, in part because of the strict criteria the authors established for determining which studies would qualify for consideration. The eligible studies had to draw from a general, nonclinical population; have a randomized, experimental design; consist of sustained interventions, not of one- shot treatments or simply of manipulations during the testing experience; and use a widely accepted, standardized mea sure of intelligence. The authors focused on experiments involving children from the prenatal period through age fi ve, and the studies meeting their requirements involved over 37,000 participants.
What did they fi nd? Nutrition affects IQ. Providing dietary supplements of fatty acids to pregnant women, breast- feeding women, and infants had the effect of increasing IQ by any-
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where from 3.5 to 6.5 points. Certain fatty acids provide building blocks for nerve cell development that the body cannot produce by itself, and the theory behind the results is that these supplements support the creation of new synapses. Studies of other supplements, such as iron and B complex vitamins, strongly suggested benefi ts, but these need validation through further research before they can be considered defi nitive.
In the realm of environmental effects, the authors found that enrolling poor children in early education raises IQ by more than four points, and by more than seven if the intervention is based in a center instead of in the home, where stimulation is less consistently sustained. (Early education was defi ned as environmental enrichment and structured learning prior to enrollment in preschool.) More affl uent children, who are presumed to have many of these benefi ts at home, might not show similar gains from enrolling in early education programs. In addition, no evidence supports the widely held notion that the younger children are when fi rst enrolled in these programs the better the results. Rather, the evidence suggests, as John Bruer argues, that the earliest few years of life are not narrow windows for development that soon close.
Gains in IQ were found in several areas of cognitive training. When mothers in low- income homes were given the means to provide their children with educational tools, books, and puzzles and trained how to help their children learn to speak and identify objects in the home, the children showed IQ
gains. When mothers of three- year- olds in low- income families were trained to talk to their children frequently and at length and to draw out the children with many open- ended questions, the children’s IQs rose. Reading to a child age four or younger raises the child’s IQ, especially if the child is an active participant in the reading, encouraged by the parent to elaborate. After age four, reading to the child does not raise
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IQ but continues to accelerate the child’s language development. Preschool boosts a child’s IQ by more than four points, and if the school includes language training, by more than seven points. Again, there is no body of evidence supporting the conclusion that early education, preschool, or language training would show IQ gains in children from better- off families, where they already benefi t from the advantages of a richer environment.13
Brain Training?
What about “brain training” games? We’ve seen a new kind of business emerge, pitching online games and videos promis-ing to exercise your brain like a muscle, building your cognitive ability. These products are largely founded on the fi ndings of one Swiss study, reported in 2008, which was very limited in scope and has not been replicated.14 The study focused on improving “fl uid intelligence”: the facility for abstract reasoning, grasping unfamiliar relationships, and solving new kinds of problems. Fluid intelligence is one of two kinds of intelligence that make up IQ. The other is crystallized intelligence, the store house of knowledge we have accumulated through the years. It’s clear that we can increase our crystallized intelligence through effective learning and memory strategies, but what about our fl uid intelligence?
A key determiner of fl uid intelligence is the capacity of a person’s working memory— the number of new ideas and relationships that a person can hold in mind while working through a problem (especially with some amount of distraction). The focus of the Swiss study was to give participants tasks requiring increasingly diffi cult working memory challenges, holding two different stimuli in mind for progressively longer periods of distraction. One stimulus was a sequence of
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numerals. The other was a small square of light that appeared in varying locations on a screen. Both the numerals and the locations of the square changed every three seconds. The task was to decide— while viewing a sequence of changed numerals and repositioned squares— for each combination of numeral and square, whether it matched a combination that had been presented n items back in the series. The number n increased during the trials, making the challenge to working memory progressively more arduous.
All the participants were tested on fl uid intelligence tasks at the outset of the study. Then they were given these increasingly diffi cult exercises of their working memory over periods ranging up to nineteen days. At the end of the training, they were retested for fl uid intelligence. They all performed better than they had before the training, and those who had engaged in the training for the longest period showed the greatest improvement. These results showed for the fi rst time that fl uid intelligence can be increased through training.
What’s the criticism?
The participants were few (only thirty- fi ve) and were all recruited from a similar, highly intelligent population. Moreover, the study focused on only one training task, so it is un-clear to what extent it might apply to other working- memory training tasks, or whether the results are really about working memory rather than some peculiarity of the par tic u lar training. Finally, the durability of the improved per for mance is unknown, and the results, as noted, have not been replicated by other studies. The ability to replicate empirical results is the bedrock of scientifi c theory. The website PsychFileDrawer
.org keeps a list of the top twenty psychological research studies that the site’s users would like to see replicated, and the Swiss study is the fi rst on the list. A recent attempt whose results were published in 2013 failed to fi nd any improvements
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to fl uid intelligence as a result of replicating the exercises in the Swiss study. Interestingly, participants in the study believed that their mental capacities had been enhanced, a phenomenon the authors describe as illusory. However, the authors also acknowledge that an increased sense of self- effi cacy can lead to greater per sis tence in solving diffi cult problems, encouraged by the belief that training has improved one’s abilities.15
The brain is not a muscle, so strengthening one skill does not automatically strengthen others. Learning and memory strategies such as retrieval practice and the building of mental models are effective for enhancing intellectual abilities in the material or skills practiced, but the benefi ts don’t extend to mastery of other material or skills. Studies of the brains of experts show enhanced myelination of the axons related to the area of expertise but not elsewhere in the brain. Observed myelination changes in piano virtuosos are specifi c to piano virtuosity. But the ability to make practice a habit is generalizable. To the extent that “brain training” improves one’s ef-fi cacy and self- confi dence, as the purveyors claim, the benefi ts are more likely the fruits of better habits, such as learning how to focus attention and persist at practice.
Richard Nisbett writes of environmental “multipliers” that can deliver a disproportionate effect from a small ge ne tic predisposition— the kid who is ge ne tically just a little bit more curious becomes signifi cantly smarter if she’s in an environment that feeds curiosity. Now stand that notion on its head.
Since it’s unlikely I’ll be raising my IQ anytime soon, are there strategies or behaviors that can serve as cognitive “multipliers” to amp up the per for mance of the intelligence I’ve already
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got? Yes. Here are three: embracing a growth mindset, practicing like an expert, and constructing memory cues.
