An Exploration of Activity Scheduling and Rescheduling Processes

The objective of this research is to examine processes of activity scheduling and rescheduling by experiments. Activity scheduling processes were examined by using a combination of mail surveys and telephone interviews. It was found that individuals’ schedules are hardly complete. Scheduled activities take place less than 50% of all executed activities. The incompleteness suggests that activity scheduling and execution are a concurrent process and the distiction between is vague. Activities with relatively high level of fixity (e.g., work activity, educational and organizational activities) are more likely to be executed than other activities. Routine activities are no more or less likely to be scheduled than non-routine activities. Attributes of activities differ substantially between scheduling and execution. In particular, the deviation between scheduling and execution in starting time appears to be smaller than that in duration. Two suggestions may be offered: individuals may be able to schedule starting time more precisely than duration or individuals may respond to unexpected events by adjusting activity duration first. Activity rescheduling processes were examined by asking subjects to talk aloud while completing controlled in-lab scenarios. It was found that the actual rescheduling processes deviate greatly from the ideal utility maximization framework. More specifically, it was found that subjects rarely assess the overall situation before rescheduling operations; rarely evaluate multiple alternatives that are available before rescheduling operations; rarely revise previously rescheduled activities; the search for rescheduling is multi-directional, but most forward-moving; and subjects are quite efficient in the process of arriving their final revised schedules. Based on findings on activity rescheduling processes, a structure of activity rescheduling was proposed. The proposed structure adopts Hayes-Roth and Hayes-Roth’s model structure of errand planning in that it consists of several independent cognitive specialists and the flow of operation is not pre-fixed. The theory of active choice set was also proposed, asserting that subjects select which activity to be rescheduled next based upon how recently this activity is assessed.