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Jack McArdle tests outside the box

AAAS Fellow Jack McArdle is a multivariate experimental psychologist at the University of Southern California. Among his areas of interest, cognitive changes as humans age.

At first glance, it's hard to figure out why Jack McArdle made the choice he did shortly after earning his Ph.D.

He had done work in psychology and computer science at Hofstra University, and he emerged from his training with two offers: a job with the Educational Testing Service for $24,000 per year, or a postdoctoral post way out west for $12,000.

The smart money, so to speak, might have been in Princeton for $24,000 with the vaunted producers of the SAT. McArdle chose the other option. He went to work at the University of Denver for the late AAAS Fellow John L. Horn, an eccentric and somewhat frightening pioneer in the theory of multiple intelligences.

Horn's work, along with psychologists L.L Thurstone, Raymond Cattell and Richard Woodcock, forwarded the idea that intelligence should be measured both in what people know and in how they use it. Horn also classified several other components in intelligence, including visual processing, auditory processing, short-term memory, processing speed and quantitative knowledge.

Now, after decades of winning and running multi-million-dollar grant programs, McArdle has continued Horn's crusade against the use of box-score numbers in assessment, the types of scores that include composite test scores and IQs. He has even fought against using SAT scores in admissions to his own program in the Psychology Department at the University of Southern California.

To hear McArdle explain it, he could not resist Horn's ideas or his persona, which he described as sparkling. After a few years in Denver, McArdle joined the faculty of the University of Virginia, where he worked for 20 years. Then he moved to USC to work with Horn in 2005.

He started working as a data analyst on some of the problems presented by Horn in 1979.

"Cognition was a problem I thought I could solve in a weekend," McArdle says, \"and I never did."

The problem came down to so many things. Testing. Analysis of testing. Correlation and lack of correlation to different parts of the testing. Uses of analyses in public policy.

In an otherwise tidy, somewhat institutional office in a massive red-brick building on the USC campus, a few faded, battered sweatshirts hang on a hook near the door.

One of them says, \"Random State University.\" Another says, \"Meanest Deviate p < .00001.\" A third is too hard to describe to non-statisticians, but if you know the formula, it's really funny.

They're Horn's sweatshirts, of course, and they've been hanging in McArdle's office for six years since his mentor's death.

McArdle's own work doesn't just support Horn's idea that intelligence cannot be boiled down to a single congenital factor. As a statistician, data analyst and psychologist, McArdle has developed methods to measure the abilities of large populations better than ever, and to use those data to find ways to predict how an individual's cognitive abilities could decline over time.

"These large data sets could yield some spectacular insights," says Jonathan King, program director of the Division of Behavioral and Social Research for the National Institute on Aging at the National Institutes of Health.

The NIA awarded McArdle a MERIT grant to fund the Study of Cognition and Aging in the USA, a large-scale longitudinal study of adults.

McArdle's development of methods to test people faster -- in five minutes instead of 40 minutes -- is solving huge problems in finding answers to the mysteries of adult decline.

"For studies like the HRS (the Health and Retirement Study), this is a very serious issue that we have to do battle on," King says.

McArdle has shown that these large studies could produce valid results even if every adult were not tested on every question. He has also come up with ways to estimate missing data from the past through statistical modeling.

One thing McArdle's research has shown is that an individual's fund of knowledge generally increases into old age, and that so-called fluid knowledge -- or how people use it -- generally peaks before age 20 and declines throughout adulthood.

Another thing he can say with some certainty: You're not as likely to lose your mind as popular culture might have you think. If you make it to age 85, McArdle says, the odds are 50 percent that you'll receive a diagnosis of Alzheimer's Disease. As far as he can tell, the fields of genetics and neuroscience have not found reliable ways to predict outcomes from there.

McArdle encourages people to improve their mental status at 19, when it's still possible.

"You can't alter the future at 85," he says.