It takes fewer than 7000 days for a single-celled zygote to become a registered voter. Adulthood is the stage of development that begins around 18 to 21 years and ends at death. Because physical change slows from a gallop to a crawl, many of us think of adulthood as the destination to which the process of development finally delivers us, and that once we have arrived, our journey is pretty much complete. Nothing could be further from the truth because a whole host of physical, cognitive, and emotional changes take place between our first legal beer and our last legal breath.

The early 20s are the peak years for health, stamina, vigour, and prowess, and because our psychology is so closely tied to our biology, these are also the years during which most of our cognitive abilities are at their sharpest. At this very moment you probably see farther, hear better, remember more, and weigh less than you ever will again. Enjoy it while you can. Your physical peak will last for just a few dozen months more—and then, somewhere between the ages of 26 and 30, you will begin the slow and steady decline that will not end until you do. Just 10 or 15 years after puberty, your body will begin to break down. Your muscles will be replaced by fat, your skin will become less elastic, your hair will thin and your bones will weaken, your sensory abilities will become less acute, and your brain cells will die at an accelerated rate. If you are a woman, your ovaries will stop producing eggs and you will become infertile. If you are a man, your erections will be softer and fewer and farther between. Other than being more resistant to colds and less sensitive to pain, your elderly body just will not work as well as your youthful body does. But it is better than the alternative! In Canada today, 84% of males and 90% of females will reach age 65 and older. What is this stage of life like, cognitively and emotionally?

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As these physical changes accumulate, they begin to have measurable psychological consequences (Salthouse, 2006) (see FIGURE 11.16). For instance, as your brain ages, your prefrontal cortex and its associated subcortical connections will deteriorate more quickly than the other areas of your brain (Raz, 2000), and you will experience a noticeable decline on cognitive tasks that require effort, initiative, or strategy. Your memory will worsen, though not all kinds will worsen at the same rate. You will experience a greater decline in working memory (the ability to hold information “in mind”) than in long-term memory (the ability to retrieve information), a greater decline in episodic memory (the ability to remember particular past events) than in semantic memory (the ability to remember general information such as the meanings of words), a greater decline in retrieval accuracy than recognition accuracy, a greater decline in…um…something else that we cannot remember just now.

But it is not all bad news. Even though your cognitive machinery will get rustier, research suggests that you will partially compensate by using it much more skillfully (Bäckman & Dixon, 1992; Salthouse, 1987). Older chess players remember chess positions much more poorly than younger players do, but they play just as well because they learn to search the board more efficiently (Charness, 1981). Older typists react more slowly than younger typists do, but they type just as quickly and accurately as because they are better at anticipating the next word in spoken or written text (Salthouse, 1984). There is a good reason that most CEOs, prime ministers, presidents, and other decision makers are over 25. Older airline pilots are considerably worse than younger pilots when it comes to keeping a list of words in short-term memory, but this age difference disappears when those words are the heading commands that pilots receive from the control tower every day (Morrow et al., 1994). All of this suggests that older adults are compensating for the age-related declines they experience in memory and attention (Park & McDonough, 2013).

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How do they do that? As you know from the Neuroscience and Behaviour chapter, young brains are highly differentiated, that is, they have different parts that do different things. We now know that as the brain ages it becomes de-differentiated (Lindenberger & Baltes, 1994). For example, regions of the visual cortex that specialize in face and scene perception in younger people are much less specialized in older people (Grady et al., 1992; Park et al., 2004). It appears that the brain is like a group of specialists that work independently when they are young and able, but that pull together as a team when each of the specialists get older and slower (Park & McDonough, 2013). For example, when young adults try to keep verbal information in working memory, the left prefrontal cortex is more strongly activated than the right, and when young adults try to keep spatial information in working memory, the right prefrontal cortex is more strongly activated than the left (Smith & Jonides, 1997). But this bilateral asymmetry pretty much disappears in older adults, which suggests that the older brain is compensating for the declining abilities of each individual neural structure by calling on its other neural structures to help out (Cabeza, 2002) (see FIGURE 11.17). The physical machinery breaks down as time passes, and one of the ways in which the brain rises to that challenge is by changing its division of labour.

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One reason why Grandpa cannot find his car keys is that his prefrontal cortex does not work as well as it used to. But another reason is that the location of car keys just is not the sort of thing that grandpas want to spend their precious time memorizing (Haase, Heckhausen, & Wrosch, 2013). According to socioemotional selectivity theory (Carstensen & Turk-Charles, 1994), younger adults are largely oriented toward the acquisition of information that will be useful to them in the future (e.g., reading reviews), whereas older adults are generally oriented toward information that brings emotional satisfaction in the present (e.g., reading novels). Because young people have such long futures, they invest their time attending to, thinking about, and remembering potentially useful information that can serve them well tomorrow. Because older people have much shorter futures, they spend their time attending to, thinking about, and remembering positive information that serves them well today (see FIGURE 11.18).

For example, older people perform much more poorly than younger people when they are asked to remember a series of unpleasant faces, but only slightly more poorly when they are asked to remember a series of pleasant faces (Mather & Carstensen, 2003). Whereas younger adults show equal amounts of amygdala activation when they see very pleasant or very unpleasant pictures, older adults show much more activation when they see very pleasant than very unpleasant pictures, suggesting that older adults just are not attending to information that does not make them happy (Mather et al., 2004). Indeed, compared to younger adults, older adults are generally better at sustaining positive emotions and curtailing negative ones (Isaacowitz, 2012; Isaacowitz & Blanchard-Fields, 2012; Lawton et al., 1992; Mather & Carstensen, 2005). They also experience fewer negative emotions (Carstensen et al., 2000; Charles, Reynolds, & Gatz, 2001; Mroczek & Spiro, 2005; Schilling, Wahl, & Wiegering, 2013), and are more accepting of them when they do (Shallcross et al., 2013). Given all this, you should not be surprised to learn that late adulthood is consistently reported to be one of the happiest and most satisfying periods of life (see FIGURE 11.19). You should not be surprised, but then you probably are because young adults vastly overestimate the problems of aging (Pew Research Center for People & the Press, 2009) (see FIGURE 11.20).

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Because having a short future orients people toward emotionally satisfying rather than intellectually profitable experiences, older adults become more selective about their interaction partners, choosing to spend time with family and a few close friends rather than with a large circle of acquaintances. One study monitored a group of people from the 1930s to the 1990s and found that their rate of interaction with acquaintances declined from early to middle adulthood, but their rate of interaction with spouses, parents, and siblings remained stable or increased (Carstensen, 1992). A study of older adults who ranged in age from 69 to 104 found that the oldest adults had fewer peripheral social partners than the younger adults did, but they had just as many emotionally close partners whom they identified as members of their “inner circle” (Lang & Carstensen, 1994). “Let’s go meet some new people” is not something that most 60-year-olds tend to say, but “Let’s go hang out with some old friends” is. It is sad but instructive to note that many of these same cognitive and emotional changes can be observed among younger people who have discovered that their futures will be short because of a terminal illness (Carstensen & Fredrickson, 1998).

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The psychological separation from parents that begins in adolescence usually becomes a physical separation in adulthood. In virtually all human societies, young adults leave home, get married, and have children of their own. Being in a committed long-term relationship are two of the most significant aspects of adult life. Census statistics suggest that if you are right now of university-age, Canadian, then you are likely to get married at around the age of 30, have approximately 1.7 children, and consider both your partner and your children to be your greatest sources of joy. Indeed, a whopping 93 percent of (American) mothers say that their children are a source of happiness all or most of the time (Pew Research Center for People & the Press, 1997).

But do marriage and children really make us happy? Research shows that married people live longer (see FIGURE 11.21), have more frequent sex (and enjoy that sex more), and earn several times as much money as unmarried people do (Waite, 1995). Given these differences, it is no surprise that married people report being happier than unmarried people—whether those unmarried people are single, widowed, divorced, or cohabiting (Johnson & Wu, 2002). That is why many researchers consider marriage one of the best investments individuals can make in their own happiness. But other researchers suggest that married people may be happier because happy people may be more likely to get married, and that marriage may be the consequence—and not the cause—of happiness (Lucas et al., 2003). The general consensus among scientists seems to be that both of these positions have merit: Even before marriage, people who end up married tend to be happier than those who never marry, but marriage does seem to confer further benefits.

Children are another story. In general, research suggests that children do not increase their parents’ happiness, and may even decrease it (DiTella, MacCulloch, & Oswald, 2003; Simon, 2008; Senior, 2014). For example, parents typically report lower marital satisfaction than do nonparents—and the more children they have, the less satisfaction they report (Twenge, Campbell, & Foster, 2003). Studies of marital satisfaction at different points in the life span reveal an interesting pattern of peaks and valleys: Marital satisfaction starts out high, plummets at about the time that the children are in diapers, begins to recover, plummets again when the children are in adolescence, and returns to its premarital levels only when children leave home (see FIGURE 11.22). Although the proportion of stay-at-home fathers has nearly doubled in the last 20 years (from 7% to 13%) (Statistics Canada, 2012b), and the proportion of fathers assuming the role of primary caregiver for some period of time in infancy has increased ten-fold since 2000, mothers still generally do more child care than fathers. It is therefore not surprising that the negative impact of parenthood is stronger for women than for men. Women with young children are especially likely to experience role conflicts (“How am I supposed to manage being a full-time lawyer and a full-time mother?”) and restrictions of freedom (“I never get to play tennis anymore”). A study that measured the moment-to-moment happiness of American women as they went about their daily activities found that women were less happy when taking care of their children than when eating, exercising, shopping, napping, or watching television—and only slightly happier than when they were doing housework (Kahneman et al., 2004). The relationship between children and happiness seems to change after children leave home: a survey of 200 000 older people in 86 countries has shown that, independent of sex, income, or partnership status, parents of adult children are happier the more children they have (Margolis & Myrskylä, 2011).

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Does all of this mean that children cause unhappiness or happiness? Not necessarily. Because researchers cannot randomly assign people to be parents or nonparents, studies of the effects of parenthood are necessarily correlational. What does seem clear is that raising children is a challenging job that most people find especially rewarding when they are not in the middle of doing it.

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