When U.S. presidential candidate John McCain had a birthday recently, television talk-show host Jay Leno told McCain that he had planned to get him a birthday cake but that the local fire chief had objected, commenting, "That many candles?"
Indeed, 72-year-old McCain is the oldest person in U.S. history to run for the presidency, and his opponent, 46-year-old Barack Obama, once accused McCain of "losing his bearings," a polite way of saying that McCain is becoming senile. McCain, in turn, sometimes refers to Obama as "that young man with very little experience."
The age issue is one of many that will help decide the upcoming election. What's the truth about it? How much difference does age actually make in competent leadership? Does cognitive ability really decline as we age, and, if so, by how much?
The American public is predictably divided on this issue. Some believe that Obama is indeed too young to assume such high office, even though John F. Kennedy was a mere 43 when he became president. Others insist that McCain is just too old, noting that President Ronald Reagan showed clear signs of Alzheimer's disease during his second term in office, when he was in his late 70s. Barely three years out of office, Reagan's cognitive impairment had become severe.
At 55, having been a research psychologist for 30 years now, I decided to take a dispassionate look at these issues. The process proved to be painful in some respects, particularly when I took an honest look at my own declining abilities. But I have long believed that knowing is better than not knowing, no matter what the pain. And when it comes to the issue of cognitive decline, knowing might also be the best defense.
Here, in brief summary form, is what relevant research says about the usual course of cognitive abilities as we age.
First, let's consider a rather basic ability: learning. Most middle-aged people are aware that their elderly parents are mystified by the latest DVD players, PDAs, and iPods -- and that the quickest way to solve a computer problem is to ask a teenager, or even a child. Do you see the trend here? Indeed, research shows unequivocally that our ability to learn new things peaks during our teen years and declines steadily thereafter. One illustrative study, conducted by Harry Braun and Richard Geiselhart a half-century ago, even showed that classical conditioning -- that most basic of learning processes first studied by Ivan Pavlov in the early 1900s with dogs -- barely occurs at all in elderly humans.
Our ability to acquire new knowledge declines in part because of a decline in most basic memory functions. The deterioration of memory is best illustrated by looking at some old research on what researchers call "incidental" memory -- remembering that occurs automatically and without effort. Mnemonic strategies mastered as we get older can mask memory's decline; when we look at what is remembered accidentally, we get a clearer picture.
Raymond Willoughby of Clark University first studied this phenomenon in 1929. He had people copy pairs of digits and symbols and then -- without first having told his subjects that he was going to do so -- later asked them to recall which symbol had been paired with each digit. Performance on this task improved from childhood to about age 13 and then declined thereafter, and old subjects performed more poorly on this task than children did. Incidental memory was also studied in a simple but ingenious study conducted by Harold E. Jones and his colleagues in which researchers asked people emerging from a cinema to give details about the film they had just seen. Teens and people in their early twenties performed best -- and elderly people could barely remember the name of the movie without looking up at the marquis. As you age, it becomes increasingly difficult to remember things unless you make a concerted effort.
The pattern is the same on classic tests of intelligence -- tests that measure basic reasoning ability, certainly an important ability for a nation's leaders. You may have heard that "IQ" remains relatively stable throughout life, and indeed it does. That's because IQ is a quotient ("Intelligence Quotient") -- a relative measure that expresses your test score in relation to test scores of people your own age. Your IQ stays roughly the same because you stay in roughly the same place with respect to your cohort.
When you look at raw scores, however -- your actual test score before it's expressed in relative terms -- the pattern is distressing. On both the traditional intelligence tests developed by David Wechsler and the more culture-free types of tests developed by J.C. Raven and others, raw scores peak between ages 13 and 15 and decline thereafter. As Wechsler put it, after age 14, increases in mental age in succeeding half-year scores "are so small as to make them unreliable," and the highest mental age we can achieve is fifteen and a half. In other words, IQ, the relative measure, is stable only because virtually everyone in your cohort is deteriorating at about the same rate.
Findings from studies of IQ are consistent with research conducted by Swiss developmental psychologist Jean Piaget and his colleagues and students. Piaget found that the highest level of reasoning, which he called "formal operational thinking," is normally achieved by age 14 or 15 -- if it is ever achieved at all.
You may also have heard that brain size is a poor predictor of intelligence. That's true when you compare species, and this also applies to genders (no one has ever figured out what human males use all that extra brain mass for). But several studies conducted over the past decade or so show that when it comes to individuals, brain size is in fact an excellent predictor of a variety of cognitive abilities. Does brain size follow the pattern we see with intelligence and memory? Indeed it does. A recent MRI study conduced by Eric Courchesne and his colleagues at the University of California San Diego shows that brain size in humans peaks at about age 14 and declines gradually thereafter. By the time a man--such as candidate McCain -- is 70, his brain has shrunk to the size it was when he was about 3. This pattern occurs both for overall brain volume and for the all-important gray matter that contains signaling neurons.
Although not central to the cognition issue, I would be remiss in failing to point out that most of our perceptual and motor capabilities also fit this disturbing pattern: our visual acuity, overall hearing ability, ability to discriminate speech sounds (important during delicate meetings of state), touch sensitivity, and so on. Elderly people sometimes, ahem, face odor challenges because--according to a study conducted in the 1980s -- they lose much of their sense of smell in their 70s and 80s. More to the point, reaction time -- our ability to respond swiftly to sudden events, which is undoubtedly an important competency for leaders -- also follows this pattern. We react to sudden stimuli most quickly in our teens and twenties and quite slowly in old age. (A new study by George Bartzokis and his colleagues at UCLA suggests that some fine motor abilities, such as finger-tapping speed, don't start declining until age 40, but this is more relevant to pianists than presidents.)
Is the news all bad? Fortunately not. Research suggests that we do become "wiser" as we get older, meaning that we can make especially good decisions in areas where we have accumulated a great deal of specialized knowledge -- as long as we don't need to acquire a great deal of new knowledge quickly, that is. In a static world, wisdom has great value, but in a rapidly changing one, it's prudent for the old to make way for the young.
As for the candidates, Obama, as brilliant as he appears to be, has likely started having trouble finding his keys, and McCain, his courage notwithstanding, is probably little more than a ghost of his former cognitive self.
This article originally appeared in the London Times on October 25, 2008.
Epstein is a visiting scholar at the University of California San Diego and the former editor-in-chief of Psychology Today magazine. His latest books are The Case Against Adolescence: Rediscovering the Adult in Every Teen and Parsing the Turing Test: Philosophical and Methodological Issues in the Quest for the Thinking Computer.