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Abstract
This thesis investigates the nature of the relationship between early life environment and executive functioning in a sample (n = 101) of Aboriginal and non-Indigenous young people (Age: M = 17.46, SD = 2.71) from primarily disadvantaged backgrounds. Results presented in the thesis are the product of replicating Miyake et al.’s (2000) experiments in a cohort of young people that differ from Miyake’s on a range of significant factors. The aims of the research were to 1) test the premise that sociodemographic grouping has a qualitative effect on executive functioning task performance, and 2) to quantify the effects of individual-, family-, and community-level factors on executive functioning task proficiency.
Initial analyses focusing on associations between executive functioning task performances produced two significant findings: The first was that the Miyake et al. three-factor executive functioning model (Inhibition, Switching, and Updating) was replicated in the current sample. The second is that the pattern of inter-task associations demonstrated in the non-Indigenous sample was replicated in the Aboriginal sample. Model fit statistics broadly support configural invariance of executive functioning tasks.
The second phase that focused on quantifying the effects of capacity, affiliation and environment factors on executive functioning task proficiency produces a further list of significant findings. Preliminary between-group analyses revealed positive statistically significant effects of differences in familial socioeconomic status (SES) and level of general cognitive ability (g) on executive functioning task proficiency. Subsequent Hierarchical Linear Modelling (HLM) suggested that individual-level (preterm birth, head injury, and childhood health), and family-level (familial SES, sibship size, and sole parent), but not community-level factors, accounted for substantial variance in executive functioning task performance. The results suggest that factors underlying the relationship between early life environment and executive functioning predominantly lie between, not within, families. Subsequent models indicate that g makes an independent contribution to understanding the nature of executive functioning, but does not fully account for the relationship between early life experience and executive functioning proficiency.
Taken together, the studies presented in this thesis suggest that the relationship between early life environment and executive functioning proficiency is quantitative rather than qualitative; those from more advantaged backgrounds perform better on executive functioning tasks, perhaps as the results of characteristics that differ between families.