The relationship between working memory and sustained attention

Working memory (WM) is related to sustained attention. The resource depletion theory assumes that overloading working memory capacity (WMC) due to resource depletion results in poor sustained attention. However, the mindlessness theory suggests that when task is easy, lower intrinsic motivation leads to decreased sustained attention. Furthermore, the maintenance and disengagement theory suggests that attention control drive the relationship between WMC and fluid intelligence. However, previous research often conceptualises sustained attention as attention control. The first aim of this thesis is to test the resource depletion and mindlessness theory to understand under which conditions (set size, time-on-task and intrinsic motivation conceptualised as effort, perceived competence and interest) the relationship between individual differences in WMC and individual differences in sustained attention is strongest. We also aim to investigate whether sustained attention differs from attention control, and if so, whether sustained attention explains the relationship between WMC and fluid intelligence after accounting for attention control. In Chapter 2, we found that set size and effort moderated the relationship between WMC and sustained attention, that is, when the task was difficult (set size 6) and effort was low, there was no relationship between WMC and sustained attention. However, time-on-task, perceived competence, and interest did not have a moderating effect. In Chapter 3, we found that sustained attention was distinct but related to attention control. Neither sustained attention nor attention control mediated the relationship between WMC and fluid intelligence. This thesis tentatively supports the mindlessness theory and challenges the predominant theory that attentional processes are the main factor driving the association between WMC and fluid intelligence.