Previous multitasking research has demonstrated a need to consider people's task-scheduling strategies when characterizing cognitive software and hardware limitations. The present dissertation reports three projects that, together, help illuminate the nature of such strategies.

The first project revealed that people tend to choose scheduling strategies that maximize their monetary reward for making precisely timed physical responses. Using a simple reaction-time (RT) procedure that required two key presses with rewards based solely on the inter-response interval (IRI) and order of responses, we found that participants adapted their RT and accuracy to the payoff. Participants who were given payoffs that emphasized shorter IRIs were both faster and less accurate than those who were given payoffs that emphasized accuracy. We formulated mathematical models of optimal strategy in terms of the external payoff and total level of internal and external system noise. Model-date fits indicated that people adapted near optimally to low and medium but not high levels of external noise.

The second project examined scheduling strategies for dealing with task interruptions. We found a significant slowdown in task interruptions when the interrupted and interrupting tasks had the same response modality, but that there was no such slowdown when the tasks had different response modalities. We developed computational models based on the CORE (Constraint-based Optimizing Reasoning Engine) theoretical framework to account for results from a representative task-interruption procedure. We found that motor preparation may begin "locked" for an interrupted task and "unlocked" only after a subsequent control signal is received from a process in the interrupting task.

The third project further investigated possible sources of individual differences in multitasking. Previous research has shown that collectivist cultures encourage "holistic" cognition strategies whereas individualistic cultures encourage "analytic" strategies. We reasoned that holistic cognition should aid people in performing two tasks simultaneously, whereas analytic cognition should aid people in switching between two tasks. Evidence from time-sharing and task-switching experiments supported this hypothesis. Japanese participants preferred simultaneous multitasking, whereas American participants preferred sequential multitasking.

Our research provides important techniques to disentangle cognitive structural limitations from software limitations for explaining people's strategic choices.