such as those strongly related to fluid intelligence (Bosman & Charness, 1996; Dixon & Backman, 1995; Kramer & Willis, 2002; Masunaga & Horn, 2001; Morrow et al., 2003). In other words, older adults may be compensating for underlying decline by relying more on their experience.

Notice that the different developmental trajecto­ries for expertise and basic information-processing abilities apparently mean the two are not strongly related. How can this be? Rybash, Hoyer, and Roodin

(1986) proposed a process called encapsulation as the answer. The term encapsulation refers to the idea that the processes of thinking (such as attention, memory, and logical reasoning) become connected to the products of thinking (such as knowledge about world history). This process of encapsulation allows expertise to compensate for decrements in underly­ing processing ability, perhaps by making thinking in the particular domain more efficient.

Encapsulation reflects the fact that in adult­hood knowledge becomes more and more special­ized based on experience, which in turn reflects a lesser role of age-related neurological development and social demands for increased specialization of knowledge and expertise (Hoyer & Rybash, 1994). The emergence of encapsulated knowledge, unique to adulthood, becomes increasingly complex and resistant to change. Because it is experientially based, the development of cognition in adulthood is directed toward mastery and adaptive competency in specific domains, making it quite different from cognitive development during childhood, which is more genetically driven and uniform across con­tent domains (Hoyer & Rybash, 1994). Knowledge encapsulation also implies that the notion of a general slowing of processing underlying cognitive

changes in later life may be wrong. Research exam­ining processing in different domains indicates that speed of processing differs across knowledge domains (Clancy & Hoyer, 1994). These find­ings indicate that the efficiency of the underlying mechanics (e. g., neural pathways), procedures, or computations required to carry out cognitive tasks depends on the amount of experientially acquired knowledge a person has in that domain.

Knowledge encapsulation has important impli­cations for studying intellectual development in adulthood. Encapsulated knowledge cannot be decomposed to study its constituent parts, meaning that mechanistic approaches (such as the one used in the psychometric research we examined earlier in this chapter) or ones predicating across-the-board declines are inappropriate. Rather, approaches that take a more holistic view and that stress develop­ing formal models of computational processes with a specific domain in particular contexts are more appropriate (Hoyer & Rybash, 1994).

In the next section, we will also see how the role of experience in cognitive development is changing the way we conceptualize wisdom. As we will see,
wisdom is more closely associated with having cer­tain types of experiences than it is with age per se.