Mental effort and sustained perceptual-motor performance
The thesis is concerned with the concept of mental effort and sustained perceptual-motor performance. It is proposed that mental effort represents a finite resource which is capable of modulating those cognitive operations underlying perceptual-motor performance. In addition, it is hypothesised that mental effort investment is associated with a number of energetical costs. This finite quality of effort is used to justifY a self-regulatory mechanism designed to ensure that effort is deployed in a rational fashion. A model of mental effort regulation is proposed based on a process of self-appraisal. This process is informed via feedback from external sources (concerned with performance effectiveness) and internal symptoms (concerned with energetical state and personal discomfort). Both sources offeedback are amalgamated into a cognitive-energetic appraisal, which represents the basis for the formulation of effort policy, i.e. whether to increase, decrease or sustain current level of mental effort. This model is explored via four experimental studies of sustained perceptual-motor performance. An initial laboratory study investigates the influence of individual differences and sleep deprivation on effort regulation. This study revealed that low performance capacity is associated with an increase of mental effort investment. The fol1owing two studies are concerned with driving behaviour. An experiment contrasting the influence of sleep deprivation and alcohol on driving performance illustrates the influence of external and internal feedback on effort regulation. The fol1owing experiment investigates this issue in detail by exposing drivers to objective performance feedback during a sustained 'journey'. A final laboratory study provides evidence that mental effort is a finite commodity and il1ustrates a number of alternative effort policies in action. These findings and their implications for the model of mental effort regulation are discussed.