Focus on driving: how cognitive constraints shape the adaptation of strategy when dialing while driving

We investigate how people adapt their strategy for interleaving multiple concurrent tasks to varying objectives. A study was conducted in which participants drove a simulated vehicle and occasionally dialed a telephone number on a mobile phone. Experimental instructions and feedback encouraged participants to focus on either driving or dialing. Results show that participants adapted their task interleaving strategies to meet the required task objective, but in a manner that was nonetheless intricately shaped by internal psychological constraints. In particular, participants tended to steer in between dialing chunks of digits even when extreme vehicle drift implied that more reactive strategies would have generated better lane keeping. To better understand why drivers interleaved tasks at chunk boundaries, a modeling analysis was conducted to derive performance predictions for a range of dialing strategies. The analysis supported the idea that interleaving at chunk boundaries efficiently traded the time given up to dialing with the maintenance of a central lane position. We discuss the implications of this work in terms of contributions to understanding how cognitive constraints shape strategy adaptations in dynamic multitask environments.