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The two types of intelligence
Strep throat may cause "mental illness"
Special Report: The Brain
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Why kids beat adults at video games

The 2 types of intelligence

espite what you may have heard about how we lose 100,000 brain cells from aging each year, the newest studies tend to show no appreciable decline over most people's life span.

But there are big age differences in your two types of intelligence:

• "Fluid intelligence" depends on brute processing ability, how quickly and accurately you learn information and solve problems. Fluid intelligence starts to decline by our 30s, partly because our nerve conduction slows. We can still solve problems well - but we need a bit more time. Reaction time slows, one reason your 10-year-old can beat you in video games.

• "Crystallized intelligence" is accumulated knowledge. It increases with age and experience. Example: vocabulary. Crystallized intelligence is why, video game ineptitude notwithstanding, you would make a better Supreme Court justice than your 10-year-old.

  Net result of the ups and downs in these two types of intelligence: Your overall IQ remains relatively steady until very late in life.

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BREAKTHROUGH

Strep throat can make a few children "mentally ill"

Then one morning he awoke with a terrifying lack of motor control. He fell against walls and tried to feed himself with great swooping arm movements that failed to find his mouth. The boy's doctor quickly arranged for him to be seen by Susan Swedo, M.D., and other researchers at the National Institute of Mental Health, near Washington, D.C.

Swedo has researched obsessive-compulsive disorder in children since the late 1980s. "When I started my research, the dominant theory about what caused OCD was punitive toilet training," says Swedo, co-author of a fascinating new book, Is It "Just a Phase"? (Golden Books, 1998). "We've come a long way in 10 years."

An amazingly long way: Swedo's groundbreaking work implicates the body's immune response to a strep infection as the likely culprit in up to 15 percent of pediatric OCD cases. (Note: If your child gets strep throat, don't be alarmed unless he or she later develops neurological problems.)

To cure this boy, his blood was filtered for two weeks to remove a specific antibody his immune system created to fight the strep - but which also attacked his brain.

"The reason for hope today is just tremendous," Swedo says. "I fully expect that in the next 10 years we'll be able to protect many children from OCD and other neurological problems."

By Jim Thornton
Thornton received a 1998 National Magazine Award for health reporting.