Dialing while driving? A bounded rational analysis of concurrent multi-task behavior

When people conduct multiple tasks in tandem, such as dialing a cell phone while driving a car, they often interleave the two tasks, for instance by returning attention to the primary driving task after entering bursts of three of four digits at a time. In order to explain why people tend to interleave these tasks at this particular interval, a control model of steering behavior is described that focuses on understanding how environmental and psychological constraints interact to determine driver performance. We use this model to predict the amount of time that people are prepared to stray from the driving task while engaging in a secondary in-car task and, by consequence, the degree of task interleaving. In particular, a modeling experiment was conducted to determine the consequences of systematically varying the time interval between consecutive steering updates for driving performance. The results of this analysis were then used to demonstrate why returning attention to driving after entering bursts of three of four digits at a time is a particularly efficient strategy: It does not allow driving performance to become too egregious, while at the same time keeping the additional time costs that are incurred as a result of interleaving tasks minimal.