Abstract

This thesis brings together two broad subdisciplines of psychology--cognition and motivation--in order to explore how motivational processes interact on-line with cognitive mechanisms in directing human behaviour and performance. A series of five experiments were conducted in which the Rogers and Monsell (1995) task switching paradigm was combined with motivational manipulations involving earned point incentives (Derryberry, 1993) to investigate the effects of prior and current motivation on task execution, attention switching, and inhibition. Using a left/right button press, participants alternated every second trial between vowel/consonant (letter task) and even/odd (digit task) judgments in response to target-foil stimulus pairs (e.g., A3, G#, ?6) presented on a computer monitor. Participants responded to the letter or digit target while inhibiting the competing (letter or digit) or neutral (symbol) foil. Task motivation was manipulated by assigning participants equal or differential incentives for letter and digit task performance during an initial training phase or during the switch task itself. Motivational incentives were found to have a large and selective influence on attention switching, evidenced by faster switching to the high-valued than low-valued task, but had no effect on either simple task execution processes or the inhibition of task-set cuing by a competing foil. In addition, prior motivational experience with differential task incentives during training had a greater and more reliable impact on attention switching than did current differential incentives applied during the switch task itself. These results reveal that motivation does not simply have a global facilitating influence on performance, but rather operates through highly specific mechanisms to bias goal-directed behaviour. Results are interpreted in terms of the apparent differential sensitivity to motivational input exhibited by attention control mechanisms versus automatic, stimulus-triggered processes. A further distinction is made between implicit motivational modulation of executive control mechanisms versus the engagement of an optional, incentive-based performance strategy. Also discussed are speculations regarding underlying neural mechanisms mediating these motivational influences on attention and the potential implications of these results for skill development and performance.