Cognitive control of internally-guided behaviours
Acting according to one's own internal goals is crucial to flexible behaviour. Clinical and lesion studies of patients with frontal lobe damage have demonstrated syndromes potentially resulting from deficits in the cognitive control system for internally-guided behaviours. Some patients can perform well on tasks that are well-constrained by the environment, including standard measures of IQ, yet show impairments in everyday life and laboratory equivalent ill-structured tasks that make planning and self-cueing demands. This thesis is concerned with the executive control of such tasks in the healthy population. Eight experimental studies are reported which consider the role of endogenous and exogenous cueing in prospective memory (PM) and multitasking. Experiments 1-4 integrated the two standard laboratory-based paradigms of task-switching and PM to assess the independence of processes involved in externally-cued task-switching and self-initiated (i.e. internally-generated) PM task switches. These experiments suggested that these two types of task switches are enabled by independent processes. Focusing only on PM, Experiments 5-6 manipulated the degree of internal cueing required by the PM task and analysed the effects on performance of the ongoing task. Participants exhibited poorer ongoing task performance in a time-based PM task without the presence of a clock (internally-cued) compared with PM tasks with stronger external cues (with a clock and event-based). The results support the view that the executive processes recruited for PM tasks reflect the demands made on internal control. In Experiments 7-8, individual * differences in internally-guided control processes were explored after development of an advanced multitasking test (AMT) for the healthy population. AMT performance correlated with some real-life outcome measures. The evidence in this thesis supports the suggestion that different executive processes are employed depending on the demand for internally- generated behaviour. Individual variation in the cognitive control system for internally- guided behaviour may relate to everyday functioning.