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Remember from Chapter 7 that, when psychologists measure intelligence during childhood, they look mainly at how elementary schoolers perform on standard intelligence tests. Sometimes, they spell out different ideas about what it means to be smart, such as Gardner’s multiple intelligences or Sternberg’s successful intelligence. Developmentalists use standard IQ tests and nontraditional strategies to trace adult intelligence, too.

Think of your intellectual role model. Most likely, your mind will immediately gravitate to someone who is 50 or 80—not a person who is 20 or 25. In fact, if you are like most adults, you probably assume that, in general, people get more intelligent over the years (Sternberg & Berg, 1992).

Mid-twentieth-century psychologists had a different idea: They believed that people reach their intellectual peak in their twenties, and then intelligence steadily declines (Botwinick, 1967). They based these disturbing conclusions on studies using the (at the time) newly developed Wechsler Adult Intelligence Scale.

The Wechsler Adult Intelligence Scale (WAIS) , the standard test measuring adult IQ, has a similar format as the WISC, the scale for children, described in Chapter 7. It has verbal items testing different types of knowledge, such as vocabulary and adults’ ability to solve math problems. It also asks test takers to perform relatively unfamiliar nonverbal activities quickly, such as putting together puzzles or arranging blocks. On this part of the test, called the performance scale, speed is essential. People must complete these tasks within a limited time.

When psychologists tested adults to derive their standards for how people should normally perform on the WAIS at different ages, they discovered that, starting in the twenties, in each older age group, average scores declined. They also found the interesting pattern in Figure 12.2 below. While scores on the verbal sections stayed stable or declined to a lesser degree, average scores on the performance scale steadily slid down, starting in people’s twenties (Botwinick, 1967).

These findings would not give any fifty-something student, like Jamila in the introductory chapter vignette, confidence about venturing into a college classroom full of 20-year-olds. Luckily, however, the researchers were ignoring the huge educational differences between different cohorts at that time in U.S. history. While virtually all of the young test takers had gone to high school, many middle-aged or elderly people taking the original WAIS had probably left school in seventh or eighth grade. So the psychologists were comparing apples to oranges—adults with less education to those with much more.

How does our performance on standard intelligence tests really change as we travel through adult life? To answer this question, in the early 1960s, researchers began the Seattle Longitudinal Study —the definitive study of intelligence and age (Schaie, Willis, & Caskie, 2004; Schaie & Zanjani, 2006).

Imagine being a twentieth-century researcher interested in charting how people change intellectually during adulthood. If you were to carry out a cross-sectional study—comparing different age groups at the same time—your findings would be biased in a negative way. Older cohorts would be at a disadvantage, not having had as much experience taking tests, typically having gone to school for far fewer years. But if you carried out a longitudinal study, you would end up with a far-too-positive portrait of how the average person changes. The volunteers who enrolled in your study would probably be highly educated. Over the years, as people dropped out of your research, you would be left with an increasingly self-selected group, the fraction of older people who were proud of proving their intellectual capacities and—as they reached their seventies—those healthy enough to take your tests (Baltes & Smith, 1997).

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Faced with these contrasting biases (longitudinal research will be too positive; cross-sectional research will be biased in a negative way), the researchers devised a brilliant solution: Combine the two kinds of studies, factor out the biases of each research method, and isolate the “true” impact of age on IQ.

First, the research team selected people enrolled in a Seattle health organization who were 7 years apart in age, tested them, and compared their scores. Then, they followed each group longitudinally, testing them at 7-year intervals. At each evaluation, the psychologists selected another cross-sectional sample, some of whom they also followed over time.

Using an IQ test that, unlike the WAIS, measured five basic cognitive abilities, the researchers got a more encouraging portrait of how we change intellectually—one that fits our intuitive sense of how we should perform. Notice in looking at Figure 12.3 that, on this measure—involving, for instance, tests of vocabulary and our ability to quickly think up words—we reach our intellectual peak during our forties and early fifties (Schaie, 1996; Schaie, Willis, & Caskie, 2004). Still, the Seattle study showed the same pattern researchers first found on the WAIS. On tests measuring people’s store of knowledge, such as vocabulary, scores improve till at least age 60 (Larsen, Hartmann, & Nyborg, 2007). But when a test involves doing something new very fast (such as arranging puzzles within a time limit or the word fluency measure in Figure 12.3), losses start as early as the forties (Ardila, 2007). Now, let’s look at a theory that makes sense of these findings and tells us a good deal about our intellectual abilities in the real world.

Two Types of Intelligence: Crystallized and Fluid Skills

Psychologists today typically divide intelligence into two categories. Crystallized intelligence refers to our knowledge base, the storehouse of information that we have accumulated over the years. The verbal scale of the WAIS, with its tests of vocabulary and math, mainly measures crystallized skills. Fluid intelligence involves our ability to reason quickly when facing new intellectual challenges. The WAIS performance scale, with its emphasis on putting together blocks or puzzles within a time limit, tends to measure fluid skills.

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Fluid intelligence—because it depends on our nervous system being at its biological peak—is at its high point in our twenties and then declines. Because it measures the knowledge that we have amassed over years, crystallized intelligence tends to increase into late middle age. However, by later life, crystallized IQ declines, because our forgetting rate outpaces the new knowledge that we can absorb.

The good news is that, with regard to the most vital crystallized skill—negotiating relationships—age losses may not appear. While their slower information processing skills can impair older people’s performance on standard theory of mind tasks (Henry and others, 2013), sixty-somethings seem just as good (or better) at judging people as younger adults (Hess & Smith, 2014). Plus, the losses on fluid intelligence tests are not as great for my baby boom cohort as for my parents’ generation (Zelinski & Kennison, 2007), suggesting that the Flynn effect (mentioned in Chapters 1 and 7) also applies to the older years. The bad news is that the inevitable age-related losses on fluid IQ tests reflect a slowing of information processing that extends to many areas of life.

So, in any situation requiring multitasking, people may notice their abilities declining at a relatively young age. In your late thirties it seems harder to dribble a basketball while keeping your attention on the opposing team. You are having more trouble juggling cooking and having conversations with guests at your dinner parties than at age 25. In old age, these steady fluid losses, as you will see in Chapter 14, progress to the point where they truly interfere with daily life.

The distinction between fluid and crystallized intelligence accounts for why people in fast-paced jobs, such as air-traffic controllers, worry about being over the hill in their forties. It makes sense of why airline CEOs or professors reach their professional peak in their early sixties (but not much beyond!). Anytime an activity depends heavily on quickness, being older presents problems. Whenever an intellectual challenge involves stored knowledge, people improve into their fifties and beyond.

Suppose you are an artist or a writer. When can you expect to do your finest work? Researchers find that when a creative activity is dependent on being totally original, such as dancing or writing poetry, people tend to perform best in their thirties (see Simonton, 2007). If the form of creativity depends just on crystallized experience, such as writing nonfiction or, in my case, producing college textbooks (yes!), people perform at their best in their early sixties (Simonton, 1997, 2002). But in tracing the lives of people famous for their creative work, one researcher discovered that who we are as people, or our enduring abilities, outweighs the changes that occur with age. As Figure 12.4 shows, true geniuses outshine everyone else at any age (Simonton, 1997).

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So, creatively or career-wise, expect to reach your peak in middle age (in most fields). Still, as you saw earlier with personality, expect to be the same person—to a large degree—as when you were younger. If you are exceptionally competent and creative at 30, you can stay exceptionally competent and creative at 70, or even 95. To illustrate this point, here are quotations from an interview study of creative people over age 60 (Csikszentmihalyi, 1996):

The poet Anthony Hecht, at age 70, commented:

I’m not as rigid as I was. And I can feel this in the poems . . . . They are freer metrically, . . . The earliest poems that I wrote were almost rigid in their eagerness not to make any errors. I’m less worried than that now.

(p. 215)

And the historian C. Vann Woodward, at the time in his mid-eighties, said:

Well, [today] I have . . . changed my . . . conclusions. . . . For example, that book on Jim Crow. I have done four editions of it . . . , and each time it changes . . . largely from criticisms that I have received. I think the worst mistake you could make as a historian is to be . . . contemptuous of what is new. You learn that there is nothing permanent in history. It’s always changing.

(p. 216)

From Sigmund Freud, who put forth masterpieces into his eighties, to Frank Lloyd Wright, who designed world-class buildings into his ninth decade of life, history is full of examples showing that creativity can burn bright well into old age.

Staying IQ Smart

Returning to normally creative people, such as you and me, what qualities help any person stay cognitively sharp? What causes our intellectual capacities to decline at a younger-than-normal age?

HEALTH MATTERS. As our mind and our body are “all connected,” the first key to staying intelligent as we age lies in staying physically fit. Hundreds of studies show that physical interventions, as varied as Taekwondo (van Dijk, Huijts, & Lodder, 2013) to resistance exercise (Chang and others, 2014), help keep intelligence fine-tuned.

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The most powerful scientific evidence that our physical state affects our thinking comes from a mammoth U.S. study tracking thousands of adults. After testing physiological functions spanning heart rate to glucose metabolism, body mass index to cortisol levels, and more, scientists devised an overall physical deterioration score they labeled allostatic load (Karlamangla and others, 2014). As you can see in Figure 12.5, this global index of body dysregulation was strongly related to performance on executive function tests. To put these findings concretely: As an adult with an allostatic load score of 2.7 (the seventy-fifth percentile), you would rank almost three years older in your ability to quickly process information than someone of the same age with a ranking of 1 (the twenty-fifth percentile)!

Even more compelling (at least for me) is an eerie phenomenon gerontologists call terminal drop. In the first longitudinal studies of cognition, researchers were astonished to discover that they could predict which older people were more likely to die within the next few years by “larger than expected” losses in their verbal IQ (Cooney, Schaie, & Willis, 1988; Riegel & Riegel, 1972). If a person’s scores on tests of vocabulary and other crystallized measures steeply declined, these changes were an ominous early warning sign of a soon-to-be-diagnosed life-threatening disease.

These studies haunted me the summer when I noticed that my father had suddenly aged mentally. My dad, who was always an intellectual whiz, had lost interest in the world. He was disoriented and depressed. A few months later, my worst fears were confirmed: My father was diagnosed with liver cancer, the illness that was to quickly end his life.

MENTAL STIMULATION (WITH PEOPLE) MAY MATTER. Because, recall from Chapter 3, environmental stimulation promotes synaptogenesis, the second key to staying intelligent should be a no-brainer: Exercise your mind!

To begin our discussion, let’s return to the Big Five—this time to openness to experience. As this trait measures our tendency to reach out and seek stimulating experiences, it comes as no surprise that adults who score high on openness are apt to grow most dramatically in crystallized IQ (von Stumm, 2013).

Professional choices make a difference. People who work in complex, challenging jobs tend to become more mentally flexible with age (Schooler, 1999, 2001; Schooler, Mulatu, & Oates, 2004). Careers involving people—from hosting talk shows, to coaching teens—are especially likely to keep midlife people mentally on their toes (Finkel and others, 2009). So, one good intellectual insurance policy is to follow my advice in Chapters 10 and 11: Find a challenging, compelling, flow- inducing career!

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But wait a second! Aren’t adults with challenging jobs apt to be intelligent and well educated to begin with, and also younger health-wise than the average person their age? Couldn’t these other forces account for why their crystallized abilities improve most with age? To prove that mental stimulation promotes cognitive growth, we might have to conduct an impossible (but fun) experiment: Assign young people to participate in a Jeopardy-like quiz show, or to host National Public Radio’s All Things Considered, then compare their IQs to those of a control group in later middle age.

The good news, however, is that while we can’t carry out this study with our species, it’s fine to experiment on rats. And, when researchers put a group of rats in a large cage with challenging wheels and swings and then compared their cortexes with control animals, this quiz show treatment produced thicker, heavier brains (Diamond, 1988, 1993). Let’s tentatively accept the widespread idea, then, that, just as physical exercise strengthens our muscles, mental exercise may produce a resilient mind. (I’d be careful about spending hours doing Suduko or other solitary brain-busting activities, however, on the principle that stimulation involving people works best.)

In sum, people in their forties and fifties are at the peak of their mental powers. But they will have more trouble mastering new cognitive challenges (those involving fluid skills) when under time pressure. To preserve their cognitive capacities as they age, people need to take care of their health and search out stimulating interpersonal and work experiences. And you can tell any worried 50-year-old family member who is considering going back to school that she should definitely go for it!

So far, I have been mainly discussing the insights related to intelligence derived from traditional IQ tests. But look back at the quotations from the older poet Anthony Hecht and the historian C. Vann Woodward, on page 371. The qualities these creative people were describing have nothing to do with putting together puzzles or blocks. What stands out about these men is their openness to experience and sensitivity to their inner lives. Given that standard IQ tests were devised to predict performance in school, perhaps it would make sense to come up with a test to capture the qualities that define thinking intelligently during adult life.

Jean Piaget described qualitative changes in cognition that occur in children as they age. So developmentalists drew inspiration from this landmark theory to construct an adult-relevant measure of IQ (Labouvie-Vief, 1992; Rybash, Hoyer, & Roodin, 1986; Sinnott, 2003).

Recall Piaget believed that we develop cognitively through hands-on experience with the world. Although Piaget thought that the pinnacle of mental development occurs when teens reach formal operations and reason like “real scientists,” wouldn’t years of living produce a more advanced kind of thinking called postformal thought? Let’s look at what separates this adult intelligence from Piaget’s formal operational stage:

POSTFORMAL THOUGHT IS RELATIVISTIC. As you saw in Chapter 9, adolescents in formal operations can argue rationally about rights and wrongs. With age and life experience, we realize that most real-world problems do not have clear-cut “right” answers. Postformal thinkers accept the validity of different perspectives. They embrace the ambiguities of life. This awareness that the truth is relative does not mean that postformal thinkers avoid making decisions or having strong beliefs. As with C. Vann Woodward, people who reason postformally make better decisions because they are open to changing their ideas when faced with competing perspectives that make sense.

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POSTFORMAL THOUGHT IS FEELING-ORIENTED. Teenagers in formal operations feel that by using logic, they can make sense of the world. Postformal thinkers go beyond rationality to reason in a different way. Because there is often no objectively “right” answer to life’s dilemmas, thinking postformally means relying more on one’s gut feelings as the basis for making decisions. As with Anthony Hecht, people who reason postformally are less rigid, more open, fully in touch with their inner lives.

POSTFORMAL THOUGHT IS QUESTION-DRIVEN. Adolescents want to get the correct answers and finish or solve tasks. Postformal thinkers are less focused on solutions. They thrive on developing new questions and reconsidering their opinions. As you saw with both Anthony Hecht and Prof. Woodward, people who think postformally enjoy coming up with new, interesting ways of looking at the world.

Clearly, we cannot measure this kind of intelligence by giving tests in which questions have a single correct answer. We need to adopt the strategy that Lawrence Kohlberg used with his moral dilemmas (recall Chapter 9): Present people with real-world situations and examine the way they think. How would you respond to this sample problem?

John is known to be a heavy drinker, especially when he goes to parties. Mary, John’s wife, warns him that if he gets drunk one more time, she will leave him and take the children. John goes to an office party and comes home drunk. Does Mary leave him? How sure are you of your answer?

If you answered this question rigidly (“Mary said she would leave, so she should; yes, I am sure I am right”), you are not thinking postformally. You must explore the consequences of leaving for Mary, for John, and for the children. You must understand that any answer you gave would be a judgment call.

Actually, astute readers may be thinking that the qualities involved in postformal thinking have uncanny parallels to the same personality attributes involved in growing emotionally with age: Be open to experience; confront and process negative life events in a thoughtful way.

Since post-formal thinking seems so linked to our enduring personality, it makes sense that simply growing older does not make people more capable of reasoning in this wiser, more “mature” way. However, one important facet of wisdom does increase in later life—our ability to take a more realistic view of societal change.

Psychologists (Grossmann and others, 2010) asked adults to talk about social/ethnic conflicts: “The Issi want to preserve that nation’s traditions, and the Assari want social change. What will happen? What would you advise?” They wondered: Would older people discuss the problem from each group’s vantage point and realize that the outcome was uncertain? Would they understand change comes gradually and stress the need for compromise?

As you can see by the blue dots in Figure 12.6, the answer was yes. Notice that a few middle-aged adults fit into the wise category. About half of elderly adults do not. But after the early sixties—wisdom takes off.

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Now, returning to what we have learned so far, what lessons does this whole chapter have for constructing a fulfilling life? Table 12.6 summarizes all of these insights in a chart that offers tips for flourishing during adult life.

Until this point, I have been discussing issues that are relevant to people in their twenties, their forties and fifties, and even adults aged 95. In the next section, I’ll explore transitions unique to the middle years.

Question 12.4

Andres will reach his career peak far earlier than Mick because his job is heavily dependent on fluid skills. A historian’s job depends almost exclusively on crystallized skills.

Question 12.5

Textbook writing is a crystallized skill, so I should be just as good at my life passion during my sixties—provided I don’t get ill. Playing video games depends heavily on fluid skills, so I will be far worse now than when I was young.

Question 12.6

The theory that applies to Rick’s problem—“too much on his plate”—is Baltes’s selective optimization with compensation: He needs to (1) prioritize and shed less important jobs,(2) work harder in his top-ranking areas, and (3) use external aids to help him cope.

Question 12.7

1. “Leave the bum!”

2. “Think of what is going on from Mark’s perspective—for instance, is he overworked?”

3. “Whatever choice you make, look at all the angles.”

4. “There may be no ‘right decision.’ Go with your gut.”

a