What Makes A Brain Gifted? (page 2)
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.
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.
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.