The ancient Greeks imagined three Fates - one spun the thread of life, the second measured its length, and the third snipped it off. Science has tried to provide more plausible (if less poetic) reasons for why some of us live longer than others. Now two researchers in Scotland have made a discovery even the Greeks couldn't have imagined: Reaction time may be a core indicator of long life.
Ian Deary, University of Edinburgh, and Geoff Der, MRC Social and Public Health Sciences Unit, Glasgow, report on a study from the MRC Unit that measured both the IQs and the reaction times of middle-aged subjects. Both tests of mental ability were associated with life span, but reaction time was the stronger indicator.
These findings, presented in the study "Reaction Time Explains IQ's Association with Death," will appear in the January 2005 issue of Psychological Science, a journal of the American Psychological Society.
The new research builds on earlier studies showing that people with lower IQs tend to die at younger ages than those with higher IQs. Deary and Der, however, wanted to use a more fundamental measure of mental ability - which they define as efficiency in processing information. They thought IQ tests might relate to physical health because people with higher IQs typically are more likely to be in occupations with safer environments. Reaction time is moderately related to IQ, but is a simpler assessment of the brain's information-processing ability - one that doesn't bear so much on other, possibly confounding factors like knowledge, education, or background.
To test their theory they examined data from the MRC Unit that, back in 1988, had 412 male and 486 female 54- to 58-year-olds living in west Scotland. The participants took both an IQ test measuring their verbal and numeric cognitive abilities and a reaction-time test that measured how quickly they pressed a button after seeing a number on a screen. The researchers also recorded the participants' gender, employment, education, and smoking status. Over the next 14 years, 185 participants died, and Deary and Der compared their test results to see if the IQ or reaction-time responses predicted their mortality.