Effects of practice, age, and task demands, on interference from a phone task while driving

Abstract

Experimental research on the effects of cellular phone conversations on driving indicates that the phone task interferes with many driving-related functions, especially with older drivers. Unfortunately in past research (1) the dual task conditions were not repeated in order to test for learning, (2) the ‘phone tasks’ were not representative of real conversations, and (3) most often both the driving and the phone tasks were experimenter-paced. In real driving drivers learn to time-share various tasks, they can pace their driving to accommodate the demands of a phone conversation, and they can even partially pace the phone conversation to accommodate the driving demands. The present study was designed to better simulate real driving conditions by providing a simulated driving environment with repeated experiences of driving while carrying two different hands-free ‘phone’ tasks with different proximities to real conversations. In the course of five sessions of driving and using the phone, there was a learning effect on most of the driving measures. In addition, the interference from the phone task on many of the driving tasks diminished over time as expected. Finally, the interference effects were greater when the phone task was the often-used artificial math operations task than when it was an emotionally involving conversation, when the driving demands were greater, and when the drivers were older. Thus, the deleterious effects of conversing on the phone are very real initially, but may not be as severe with continued practice at the dual task, especially for drivers who are not old.

Introduction

Innovative in-vehicle technologies increase the scope of activities that drivers can perform while driving. One ubiquitous manifestation of the new technologies is the in-vehicle cellular phone and the use of portable cellular phones while driving. As the number of people with cell phones increases, so does the number of drivers who use in-vehicle cell phones (Royal, 2003). From a cognitive, human-information-processing perspective, the use of the phone while driving constitutes a time-sharing situation in which driving is the primary task (hopefully) and talking on the phone is the secondary task. As such, the phone task can be distracting, disruptive to driving, and potentially dangerous (Goodman, 1997, Goodman et al., 1999). This general conclusion is supported by laboratory and driving simulation studies (McKnight and McKnight, 1993, Alm and Nilsson, 1993, Strayer and Johnston, 2001), closed track road studies (Ishida and Matsuura, 2001, Hancock et al., 2003), and open road studies (Brown et al., 1969, Harbluk et al., 2002, Patten et al., 2004).

In the paradigm common to all the experimental studies that have been reviewed (1) both the driving and the distracting ‘phone’ task are experimenter-paced (unless driving speed is one of the measures of driving performance), and (2) the studies compare the performance of one or more control conditions (e.g., no distraction) with one or more distracting conditions (e.g., math operations) in a situation where each condition is presented only once, or for one block of trials.

However, these two features – fixed paced, experimenter-controlled tasks and one trial or block of trials in each condition – are not typical of driving in general, and of driving while performing other tasks in particular. Driving and conversing on the phone are both partially self-paced tasks. Drivers can often adjust their speed to control the rate of information input, and they can often pause in the conversation or postpone a conversation when the driving task is too demanding. In addition, as in other tasks in life, our performance improves with practice and feedback so that the more practiced a task is, the more it (or parts of it) can be automated, and consequently more attentional capacity is left for other tasks. Thus, practice at a task can enable a person to time-share it effectively with other tasks (e.g. Wickens and Hollands, 1999).

In driving, much of the experience-based improvement is based on subtle and gradual changes in information acquisition and processing (Mourant and Rockwell, 1972, Shinar et al., 1998). Also, to counter overload from using the cell phone while driving, drivers often increase their safety margins by increasing headways to vehicles ahead (Brookhuis et al., 1991, Ishida and Matsuura, 2001), or by reducing their speed (Ishida and Matsuura, 2001, Waugh et al., 2000). In addition to pacing or modifying the driving, drivers can also pace the phone conversation (Waugh et al., 2000).

In 1938 concerns similar to those that are raised now with respect to cell phones, were raised with respect to allowing drivers to listen to the radio while driving (Goodman, 1997). This perspective raises the issue of whether or not introducing new cognitive tasks to the driving situation necessarily impairs driving significantly, and if so under what conditions and for how long. Like other psychomotor skills, it is possible that sharing the driving task with the listening/talking phone task can be improved with practice.

The objective of this research was to see if, when the driving task is sufficiently difficult or the driver is less capable, there is a learning effect whereby drivers learn to combine the driving task with the phone task. With respect to the distraction, we used two types of tasks: a math operations task (as in many previous studies), and an emotionally involving conversation. The math operations task has been shown to be sufficiently taxing to interfere with driving performance (McKnight and McKnight, 1993, Shinar et al., 2002), but its validity as a surrogate for a phone conversation is questionable. The conversation task has the needed ecological validity but suffers from the fact that it is much less structured and – to be emotionally involving – has to be individually tailored to each subject.