As for the complexity of the environment in which practical cognition unfolds, one variable that has been pointed out as extremely important for shaping the development of practical skills in adulthood is that of the immediate conditions and demands of work (see Schooler, in press, for a review). For example, Kohn and Schooler (1983), in a group of men between the ages of 24 to 64, longitudinally studied the link between the extent to which one's work-related activities involve independent thought and judgment and workers' flexibility in dealing with complex cognitive demands. They found that the more the substantive complexity of one's job, the greater the incremental gains in cognitive performance over a ten-year period. Even more astounding, a similar relationship between job complexity and cognitive performance was revealed for women doing complex housework (Schooler, 1984). Moreover, K.A. Miller and Kohn (1983) found that individuals with higher flexibility in dealing with complex cognitive activities tended to engage in more stimulating and demanding cognitive activities (e.g., reading books versus watching television). The major criticism of this nonexperimental evidence of the cognitive effects of doing complex work (whether in the work place or the household) is that these designs are unable to rule out the possibility that individuals who maintain their cognitive functioning are more capable of pursuing and staying in challenging work environments. Yet, even though the causal path is difficult to infer among individuals, the evidence that among individuals more cognitively complex work leads to enriched cognitive functioning deserves attention and more thorough investigation.

Regarding familiarity or experience with the domain in which practical problem solving is carried out, studies have demonstrated that cognitive performance is greater for both young and older adults when individuals are given either familiar materials (Smith and Baltes, 1990) or a chance to practice prior to assessment (Berg, Hertzog, and Hunt, 1982). Yet, results are ambiguous as to whether differential familiarity is a factor that can help to explain age differences in practical problem solving (Denney and Pearce, 1989).

Researchers reported, for example, that older adults perceived traditional cognition tests as less familiar than did young adults (Cornelius, 1984). Therefore, when younger and older adults are compared on conventional cognition tests, older adults might look worse because these tests are less familiar to them and they may have forgotten how to evoke specific strategies relevant to situations of cognitive assessment.

To explore the importance of the familiarity factor, several studies have been carried out in which younger and older adults were asked to solve problems that were constructed to be more familiar or more normative for one age group or the other. For example, Denney and colleagues (Denney, Pearce, and Palmer, 1982) showed that, in adults, the more normative for their age group everyday problems are, the better their performance is. Similarly, Smith and Baltes (1990) found that adults perform best when the problems are more normative for their age group. As Berg (in press) pointed out, memory research utilizing the usage of tasks with familiar materials (e.g., remembering words that were in frequent use during their adulthood years versus contemporary equivalents) is consistent in showing that older adults tend to perform better with materials more familiar to them (Barret and Watkins, 1986; Worden and Sherman-Brown, 1983).

1.2.2 Content of practical problem solving

The main hypothesis underlying this line of research is that the content of practical problem solving differs at different stages of development. The literature published to verify this hypothesis contains heterogeneous evidence; some is supportive (e.g., Aldwin, Sutton, Chiara, and Spiro, 1996) and some is not supportive (e.g., Folkman, Lazarus, Pimley, and Novacek, 1987) of the assertion that individuals of different ages experience different everyday problems.