The Influence of Advancing Age on Cognition
According to data from the SLS, between the ages of 60 and 74, nearly all of us will show sta- tistically significant reductions in abilities, though again, there is no universal pattern of cog- nitive decay. Even an expected comprehensive decline over the 7 years between age 74 and 81 has not been found to exist. Fewer than half of the participants in the study have showed major declines in global cognitive functioning over that period (Schaie, Willis, & Caskie, 2004). Per- haps most striking is the finding that although the majority of individuals show a significant decline in at least one primary mental ability by age 60, virtually no one in the SLS has shown declines in every area, even up to age 88 (Siegler et al., 2009). Much of the variation in out- comes could be due to an assortment of personal factors. There are individual variations in biology and genetics, personality, and relationships that influence intellectual development. For example, participating in physical exercise, which promotes cognitive health, varies by inherited athleticism, degree of self-motivation, and amount of social support.
Another important finding from the SLS was the discovery of several historical cohort effects. On numerical ability, people born between 1903 and 1924 out performed those born earlier and later; on inductive reasoning, every generation was superior to the preceding one. Ver- bal recall improved among all cohorts up to those born in 1952, but has declined since then. And, lending support to the Flynn Effect, in general, later-born cohorts have outperformed earlier born cohorts (Schaie & Zanjani, 2006). The great overall variation in results allows us to recognize what we can expect developmentally compared to what might be out of the ordinary. We cannot easily dismiss changes in memory, mood, or personality as part of the aging process. The SLS informs us that sudden cognitive declines in healthy individuals are quite unusual.
Fluid and Crystallized Intelligence Others have differentiated patterns of aging in reasoning ability versus patterns established by accumulated knowledge. Fluid intelligence refers to the ability to process information, see relationships, use abstract reasoning, and analyze information. Think of the term “fluid” as analogous to movement. It represents the ability to mentally manipulate and reorganize multiple pieces of information. In order to study fluid intelligence, adults are given spe- cific and standardized reasoning tasks that are often timed. In these controlled situations, researchers find a steady age-related drop in fluid ability beginning after age 30 or so (see Figure 9.6). According to Horn and Hofer (1992), this kind of cognition declines with age as brains become less able to hold multiple bits of information simultaneously.
In contrast, crystallized intelligence can be thought of as something durable. It can be described, like specific stores of information. For example, as people age their stored vocabu- lary and knowledge of history increases. More is learned about the events they live through as well as those they hear about. Though some information is forgotten, that which is forgotten is far surpassed by what is continually remembered. Crystallized intelligence usually grows well into later adulthood. The average 70-year-old knows more trivia and can do crossword puzzles much better than the average 30-year-old.
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Crystallized intelligence (pragmatics)
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Section 9.7 The Influence of Advancing Age on Cognition
In reality, crystallized intelligence cannot easily be separated from fluid intelligence. For example, even though a younger plumber may have superior fluid intelligence and faster reac- tion time, the acquired crystallized intelligence of a more experienced plumber is likely to be advantageous as well. In fact, when younger and older adults are compared in real-life tasks involving skills already learned, such as how to reconcile a bank statement (or fix a plumbing leak), there is little difference in abilities (Bialystok & Craik, 2006). Therefore, while some kinds of intelligence may deteriorate with age, other increases can balance out the outcomes for adults of different ages.
These examples show how both fluid and crystallized intelligences are often used simultane- ously, especially when seeking creative solutions (and can be related to Sternberg’s idea of triarchic balance). People use their crystallized, accumulated knowledge to help them rea- son abstractly and solve problems. People in their 20s who are at the “peak” of their fluid intelligence are usually not pursued to head companies; those who are just beginning higher education often seek out returning older students for their wisdom. Exercising both abstract reasoning processes and the rote memory skills indicative of crystallized intelligence rein- forces mental sharpness. Although differentiating between fluid and crystallized intelligences is important to understanding development, outside of a laboratory they cannot be easily separated.