As I've said, you cannot have functional or behavioral differences (such as being smarter) without some kind of corresponding difference in the brain from a more typical brain. As understanding of the causes of those differences improves, researchers will know better how to identify and develop them. On the whole, brain differences fall into four distinct categories. They are morphology, operations, real estate, and electro-chemical cellular functions, or M-O-R-E as a way to remember them easily.
- Morphology: Size, quantity, and shape of brain structures
- Operations: Neural efficiency and speed of internal connectivity in the brain
- Real estate: Strategic differences in which or how brain areas are used
- Electro-chemical cellular function: Differences in electrical and chemical activity
The difference most associated with gifted children is the effectiveness with which they learn; as a generalization, they pay closer attention, absorb information, stay focused, learn the interrelationships more quickly, and remember longer. Those are the observable consequences of the four differences I just described. The following sections describe how each of them plays out.
Morphology
The first category—brain morphology—refers to the shape, size, and boundaries of structures within the brain. Some correlations suggest that more brain volume equals more computing power.17 Total brain volume accounts for about 16 percent of the variance in general intelligence scores. If this study was true, you'd also expect overall head size to correlate with intelligence, and it does.18 Interestingly, students with AD/HD have both lower overall IQ scores and smaller brain volume, by 3 to 4 percent.19 Data like this suggest at least some kind of a correlation between overall computing capacity and the brain's morphology. Bigger head size does increase the chances for greater IQ. This obviously does not mean that all melon-headed kids are geniuses, but the correlations are well above chance levels.
Another set of animal studies measured (postmortem) the total number of both neurons and glial cells (the highly important support tissue) in rats. In the gifted, there were far more glial cells (more than double!) as compared with the nongifted learners. But what about humans?20 As a vivid example, when Marian Diamond studied a sample of Einstein's brain tissue in the mid-1980s, she found that his brain had more glia per neuron than did the average brain (73 percent, compared with eleven others) in one area: the left inferior parietal lobe (Figure 6.1).21 This difference exceeded the expected ranges for both age and individual variability and may be typical for the frontal area of exceptionally gifted people—or it may have been the specific area Einstein used for complex mathematical theories.
As a historical note—and evidence of the difficulty many have in accepting the idea that exceptional brains can differ physically from the norm—it's interesting to observe that Diamond's paper ran into a firestorm of publicity. Her fellow scientists concocted headlines based on her findings ("Einstein's Extra Brain Cells: The Secret to His Genius!") as icebreakers in their presentations, setting crowds of skeptical researchers roaring with laughter.22 Diamond herself never generalized her results to all geniuses, merely saying that they were potentially meaningful, and her work has since been vindicated. Today, we do know that larger numbers of glial cells are correlated with improved learning and memory.23 In another study with highly gifted individuals, there was a significantly greater level of individual variability, especially in the right hemisphere.24 This may reflect space, time, and sensory processing skills.
Surprisingly, gifted brains also include larger proportions of "extreme neurons"—those very small and very large neurons. These are ones that seem to either start off that way, enabling a greater number of connections, or develop in ways that may have some additional processing capacity. In another study that compared people with strongly creative, highly gifted talents to a control group of average performers, postmortem evidence revealed a much more customized and specialized brain.25 More cortical fields were streamlined, there were greater numbers of pyramidal neuron glial cells, and there was much greater distinctiveness of how the neurons were grouped. This suggests the extensiveness to which gifted people use particular areas of the brain. All told, the giftedness may be more likely a combination of differences or a threshold that needs to be reached. There are correlations for it in a larger-than-typical brain or in those with unusual neuronal development, and it may have more glial cells than a typical brain.
Operations
When our brains do things that we ask them to (tie our shoe, turn on the lights, figure out the change from a ten-dollar bill, type a sentence in our computer, or calculate the tip in a restaurant), we call that "brain work" an operation. Some operations are merely functional (brushing our teeth or driving our car, and so on), and others are strategic (solving a problem, calculating the odds on a decision, or figuring out how to approach a problem from another's point of view). Gifted people are usually better at working memory and attention span.
Even though the functional operations seem like they are more physical, they still involve our brains. But those can be and are typically learned by people at most levels of intelligence. The more strategic operations are different. Strategic operations are done faster and more efficiently and often more creatively by those who deserve a gifted label. The mental computations are not just "fun work" for their brains; they often do them enough so that they become automatic and fast.
Connectivity. There are between seventy-five and one hundred billion neurons in the brain and nearly a trillion glial cells. Each neuron has between several hundred and tens of thousands of synaptic connections, depending on where in the brain it is. Overall, this means the human brain has several trillion connections that enable everyday life. Neurons are linked to one another both locally and at a distance.
For comparison, think about all the technology that surrounds you right now. You needn't be deeply into the high-tech life to have a computer or two in the house, along with several phones of various types, a few TV sets (probably with DVD player and VCR), TIVO, Internet access, videogames, an iPod, and any number of other devices, from a PDA to a talking oven. Each device has different needs and varying capacity. In most homes, these separate systems don't talk to each other. Could you imagine the work in networking together all those devices in just one house, your own? This would mean a complete wireless network within your house. Let's say you did have the savvy to interface all your different types of systems into one streaming, trouble-free, seamless network. That would be tricky, but it could be done. Now add this: next you're making every bit of technology in your home talk to every bit of technology in someone's home down the street. Now add this: you're making every bit of technology in your home talk to one in three homes around the world. You've just bumped your home-networking problem into a global challenge of near-biblical proportions. If that sounds complex, that's the equivalent of what every human brain does! The gifted brain simply does it all quicker.
Does the gifted brain have a much greater number of connections as compared with a more typical brain? The answer is not known for sure, but there is speculation that the gifted brain does work faster and has up to 10 percent more connections. One wouldn't want too many connections. The human brain uses probably 30 to 40 percent of the total possible connections already.26 But a brain with too many connections would not be any smarter. In fact, at an extreme case, a child with the Fragile X Syndrome has way too many connections and is severely mentally retarded.27 Computer modeling simulations show that having some unused capacity in the brain is actually a smart concept. It gives a computational advantage for a brain that needs a high degree of flexibility in responses at the more global level.28
Therefore, it's likely that a gifted brain has the right combination of sufficient connections in the right places and high processing speed. Any brain system that has both reciprocal and sparse connections can learn faster and integrate a great deal more information than a brain that is 100 percent interconnected.
Connection and Processing Speed. Why is speed so essential? Greater complexity creates greater possibility of confusion without another key feature: connectivity. Once all the connections are in place, the next ingredient needed to make it functional is speed.
The gifted learn things more quickly, they develop and use more connections, and they have faster connections. It's as if they are using high-speed Internet access while the rest of the population is still struggling with dial-up lines. In fact, there's a decrease in cortical usage with increasing intelligence: electrical-chemical activity from pretest to posttest correlates negatively with intelligence. This suggests that the higher the subjects' general competence, the larger the decrease in the amount of cortical activation.29 These findings suggest intelligence-related individual differences in becoming neurally efficient. The brains of the gifted are just flat out faster at processing. That means they can move larger quantities of signals around more easily.
Other researchers have been more concerned with speed of processing. Two studies found different results. One found an inherited (genetic) correlation between intelligence and speed of information processing. 30 But in a practical manner, higher processing speed did not always mean faster decision making. Another group studied peripheral nerve conduction velocity and found no relation to IQ.31 In fact, in a very practical study testing for memory and speed, the higher-ability participants devoted more time to stimulus analysis and planning than did lower-ability participants, suggesting more processing time on an activity.32
Generally, the gifted have the ability to acquire new and complex information more rapidly than their average-ability peers in situations involving simple acquisition. Multiple studies have shown a stronger focus ability in those with higher IQ, suggesting an ability to filter out distractions. Higher-ability people's effectiveness in controlling attention and gating sensory information seems to be a critical factor.33 It differentiates and identifies those individuals with complex cognitive abilities.
Some correlations also show up between mental speed of processing and specific abilities. For example, musical ability, as one might guess, is correlated with higher mental speed.34 But I would also expect competencies in martial arts, race car driving, and videogames to correlate with mental speed, too. This suggests that many people who have faster mental processing may have chosen to use the advantage in nonacademic arenas. So far, human intelligence seems much like a mental juggling act in which the smartest performers use specific brain regions to resist distraction and keep attention focused on pieces of information that they regard as critical, which may or may not be anything involved with their schooling.
Global Connections. One of the keys to understanding cognition is understanding the networking operations of the brain. For the various brain areas to be most efficient, they need rapid and thorough communications. Most research has found clear links between intelligence and brain activation patterns in the frontal lobe. These make for higher-order cognitive functions. The brain has to be able to activate, process the learning, and then wait for the next activation. Sluggish learning won't work in the gifted brain. This "transient response plasticity" occurs over a very short time scale and is typically considered to be a property of higher-order, more cognitive brain regions such as the prefrontal cortex.35
It's a bit like a city; the more roads, highways, and alternative routes available, the faster anyone can get to any other place. The fewer the connections, the weaker they are, the more sluggish they are, the slower the traffic. In the brain, if you want general intelligence, connecting to the right place at a high speed is a must. As an example of connectivity, consider the brain of the severely retarded savant; the savant has great connectivity in one neighborhood of the brain, but a gifted brain is far more globally connected.
In general, the brain typically called smarter or gifted has different neural wiring (Figure 6.2). One study measured interaction between the left and right hemispheres in mathematically gifted adolescents, average-ability youths, and college students. The task showed hierarchical letter pairs in three viewing conditions: (a) only to the right hemisphere—to the subject's left side, (b) only to the left hemisphere—to their right side, or (c) bilaterally—to both hemispheres at once. Participants had to make quick letter-match or no-match judgments, and some did much better than the others.36 These data suggest to us that greater interhemispheric traffic may be a functional characteristic of the mathematically gifted brain.
Real Estate
In general, it's difficult to say that gifted people consistently use their brains differently from more typical learners. But what the research tells us is that a slew of efficiencies in the gifted brain help it use the right areas, use areas that it is very good at, and use the smallest amount of brain real estate necessary to do the task. This is important in looking at imaging studies, because the area of the brain may not light up in the same way it would for a more typical or disadvantaged learner. In fact, it may give a contradictory story that has a temporal component. Many gifted learners seem to be switching gears constantly, like an old-time car transmission, trying to get the right task into the right part of the brain. This means that the areas activated will change more dramatically during a task than would be likely among other more typical learners.
Focus That Brain! The amount of brain activation in each network depends on how skilled individuals are in verbal or visual learning. In other words, the more skilled we are in the strategy used, the less brain activation or effort is required to perform higher-level thinking tasks. When given a choice as to which thinking strategy to use, the brain often uses the method that requires the least effort, namely the strategy in which the individual is most efficient. This means that it takes greater skills to manage your own resources, even if it means damping down the emotions. Those who test higher are typically less influenced by affect (that is, by emotional state). Feeling ecstatic, very sad, or anxious all create competing stimuli for the brain to deal with. Problem solving and other processes require focus, and too much affect slows us down. In fact, neutral affect is associated with faster learning because the emotional processing is dampened.37 Having some positive affect enhances thinking, but too much affect will negatively influence cognition.
Those who are gifted tend to use their frontal lobes very effectively and to manage incoming sensory information better than those who have a lower IQ (Figure 6.3). This area is used to filter the incoming data and then figure out the task, then things literally slow down. Generally, the higher the subject's overall mental ability, the more quickly the task is mastered, and the larger the decrease in the amount of cortical activation as the subject shifts gears. These findings suggest intelligence related individual differences in becoming neurally efficient.38
Effectiveness in controlling attention and gating sensory information is a critical determinant of individual differences in complex cognitive abilities.39 To be effective at a consistently high level takes the constant engagement of higher-order brain functions to sort tasks, focus, move tasks, switch brain areas used, and process tasks quickly. Generally, those with higher and more flexible, fluid intelligence keep distracting information at bay by activating regions in both the prefrontal and parietal cortexes, as well as a number of other regions. Naturally, how well subjects perform in any given situation depends on the complex interaction of many abilities, but frontal lobe execution is paramount.
To confirm this theory, we could ask if those who have difficulty with focus and impulsivity regulation (both frontal lobe functions) do worse on IQ tests; they do! Studies of students with attention deficit tell us that for overall intellectual ability (Full Scale IQ), scores were lower for those with AD/HD than for healthy participants.40 Of course, many highly successful adults have AD/HD, but these results may tell you that they were able to compensate and beat the odds. This is just one of the many differences that crop up between paper IQ scores and real-world success.
Try Less, Accomplish More. The relationship of the more gifted with brain usage is complex and often delicate. Gifted adolescents often have a developmentally enhanced (closer to a college age) state of brain activity.41 This typically gives them unusually strong focus, motivation, and concentration on tasks for their age. In general, they have a greater "force of will" as characterized by greater left hemisphere alpha brainwave activity levels (8–12 Hz per second). As a generalization, those with lower IQ use certain areas more, to try harder, even though their efficiency in using that area is not strong. In one study, the higher-IQ subjects were found to be using an entirely different part of the brain to do a given task as compared with the lower-IQ subjects.42
Again we see the same pattern. It's not just using the frontal lobes, it's being able to use them successfully that counts. One high school boy had moderate mental retardation, with an IQ in the 70 to 80 range. But he also had exceptional calculation abilities and was referred to as a savant. When asked to perform, he actually used the frontal lobes excessively, suggesting that it was his previously diagnosed obsessive compulsive nature combined with a probable failure in his brain's central executive functioning.43 This shows the dual nature of skill and deficit; his sheer will (obsessive, in fact) forces his frontal lobes to work overtime at tasks. As you may have guessed, one could be both gifted and have a learning disability.
Overall, there appears to be support for the idea that gifted people have more balanced thinking ("whole brain" was the buzzword years ago). Some researchers contend that enhanced right hemisphere involvement during cognitive processing is a correlate of mathematical precocity.44 In addition, the general pattern of activation observed tells us that those of higher ability more effectively coordinate left and right hemisphere processing. Later studies have supported this lingering notion that gifted males have a greater reliance on their right hemisphere as a physiological correlate of mathematical giftedness.45 One older but very interesting study using EEG showed that, as compared with lower-IQ subjects, greater symmetry between hemispheres is associated with superior performance among those more gifted.46 Again we see that those with greater intellectual prowess are literally using "more" of their brain at times, while at other times they are simply integrating its areas much better.
It is also believed that the gifted use the spatial-temporal areas of the temporal lobes to support higher-level functions. Under the supervision of physicist Gordon Shaw, a group of researchers in Irvine, California, used a very challenging videogame to understand spatial-temporal reasoning. The game is based on the mathematics of knot theory and was used for understanding DNA structure prior to this application. Some elementary and middle school students showed game mastery so quickly that researchers conjectured that the spatial temporal reasoning capacity is innate.47 Is there a way you could test this theory? Could someone influence intelligence by changing where in the brain they are processing a task? Yes—in one experiment, researchers in Sydney, Australia, used electromagnetic pulses to suppress the left frontal temporal lobe for a task, forcing the brain to use the right side. In a statistically significant number of subjects, there was an increase in drawing skills (typically thought of as more right-brained) and even proofreading (very sequential task).48 These studies suggest that some strengths would be available to all of us, if we could get our brains to use the right areas for the right jobs.
Electro-Chemical Cellular Function
It turns out that brains do differ right down to the electrical and chemical levels. Researchers at the University of Tennessee did an interesting experiment using cortical event-related potential (ERP). That's the one where the subject wears that fashionable little cloth polka-dot skullcap (usually with thirty-two or more electrodes connected to the scalp) to measure electrical current. Then a stimulus is presented, and the speed, amplitude, and location of the brain's response are measured. Sensory ERPs can successfully predict differences in working memory span and fluid intelligence.49 This suggests that electrical activity is one of the indicators for efficient or effective cognitive processing.
One study used learning disabled, gifted, and typical control children of ages eight to twelve. The common "distracter" stimulus consisted of random nouns generated 80 percent of the time. The target stimulus was animal names presented the other 20 percent of the time. The research was designed to find out what differences, if any, would appear among the subject groups. There were differences, and—as you might guess—the gifted performed much better than those with learning disabilities and the typical subjects.50 But the study differences suggested the possibility of delays or gaps in the attention and information processing for those with learning disabilities. Again, it was the speed and ability to filter out and focus that made the gifted subjects do better. The electrical-chemical capacity of their brains helped create a more efficient response.
What about hormone levels—are they correlated with intelligence? The best-researched hormones are the stress and sex hormones. It is believed that those who are more intellectually curious have a lower baseline of cortisol—that's a hormone related to stress. Higher levels of cortisol are associated with a more contracted response. When we feel too stressed, we are less likely to show exploratory, curious, novelty-seeking behaviors. Those who do show this early habit of curiosity, even as three year-olds, turn out to be much more competent intellectually in later years.51
Using saliva samples, researchers measured the testosterone levels of 247 children, 100 of them gifted and the others randomly chosen. Lower salivary testosterone levels were found in intellectually gifted children of both sexes (all females have some testosterone). There was an overall negative relationship between testosterone levels and cognitive abilities in preadolescent children.52 Greater levels of salivary testosterone are correlated with lower student achievement. This is not to say that athletes are dullards; it suggests that testosterone comes with a price. Remember that with any population sample, you'll see a bell-shaped curve. Some with higher levels of testosterone may have a dozen other, far stronger factors that support a gifted brain, including high motivation and better concentration.
And finally, certain neurotransmitter levels are associated with greater intellectual performance. Having just the right levels of dopamine is associated with better frontal lobe function. Too much dopamine (the "pleasure" or "reward" neurotransmitter) is associated with schizophrenia.53 The brain's frontal lobes need just the right amount of dopamine to fuel working memory. Excess dopamine is counterproductive for cognitive processing.54 However, too little is bad, too.55 Dopamine is known as an upper for the brain; in the same way that amphetamines, cocaine, and caffeine ramp up the activity of the prefrontal cortex, dopamine does also. It just does it in a more sane way.
There's no doubt that highly intelligent, gifted thinkers display a greater degree of cognitive flexibility. Gifted thinking requires just the right amount of serotonin. That's the neurotransmitter associated with mood, memory, and attention. Those with little flexibility typically are lower in serotonin. Studies show that cognitive inflexibility is typical after prefrontal serotonin depletion.56 Serotonin depletion can be influenced by dietary changes. Foods with a higher amount of the amino acid tryptophan (used to make serotonin in the brain) include bananas, turkey, milk, and avocados. Creative problem solving is improved when serotonin is at the middle healthy level. Together with increased dopamine release for better processing speed and attention, serotonin improves the flexibility needed for maximum cognitive achievement.
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