Date of Award
Doctor of Philosophy
Intelligence and executive functioning are multidimensional, related constructs (Decker, Dean, & Hill, 2007; Miyake, Friedman, Emerson, Witzki, & Howerter, 2000). Research suggests that fluid intelligence and certain components of executive functioning are related, with an emphasis in the literature placed on the relations between fluid intelligence and working memory (Salthouse, 2005; Salthouse & Davis, 2006). However, limited published research exists about the relations between fluid intelligence and other components of executive functioning. There also is debate in the literature about the relations between crystallized intelligence and executive functioning (Friedman et al., 2006). Some researchers suggest that the two are not related (Pennington, 1994), whereas others propose that there are relations between the constructs (Cowan, 1995). However, beyond working memory, limited information exists about the relations between crystallized intelligence and other executive functioning components. Denckla (1996) proposed that the relations between fluid intelligence and components of executive functioning are gradated; however, this area of research is limited. Furthermore, no study was found that reported gradated relations between multiple components of executive functioning and crystallized intelligence. Therefore, the primary purpose of this study was to examine the potentially gradated relations between fluid and crystallized intelligence with multiple components of executive functioning with the same sample. Findings from my study indicated that the relations between fluid and crystallized intelligence and components of executive functioning are gradated. Some executive skills shared similar relations with the intelligence constructs, whereas other relations were unique. It was found that Working Memory/Shifting shared similar relations with fluid and crystallized intelligence constructs. In addition, unique relations also were found between Problem Solving/Planning and fluid intelligence and between Nonverbal Fluency/Inhibition and crystallized intelligence constructs. This indicates that there are common and unique neurocognitive relations between aspects of executive skills and intelligence. Furthermore, the relations between fluid and crystallized intelligence and components of Baddeley's working memory model also were tested. Relations were found between visuospatial working memory and fluid intelligence; however, no other relations were found. To provide some clinical insight, the relations between multiple executive skills and a standardized academic achievement measure (ACT) also were examined while controlling for fluid and crystallized aspects of intelligence. It was found that controlling for crystallized intelligence yielded better understanding about the relations between executive functioning and academic achievement. Overall, across the analyses conducted within this study some findings replicated existing information in the literature and new findings were found that contribute to the literature. The benefits, clinical implications, and limitations of this study are discussed. Suggestions for future research also are provided.
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