Cell Phone vs. Passenger Conversations and Driving Performance

Theory Under Investigation

Reference: Drews, F. A., Pasupathi, M., & Strayer, D. L. (2008). Passenger and cell phone conversations in simulated driving. Journal of Experimental Psychology: Applied, 14(4).

The research focuses on the three levels of performance theory as it pertains to the driving task. The first level is operational, or control-level, performance. This level involves keeping the car on a chartered course; when compromised, the car will veer or drift. Prior studies have shown that talking on a cellular phone while driving impairs operational performance.

The second level is tactical behavior, which "involves skills needed for maneuvering the vehicle in traffic" (Drews, Pasupathi & Strayer, 2008, p. 392). Impairment in tactical behavior means not paying adequate attention to other drivers, particularly at intersections. Irregular acceleration and slow reaction times are also signs of diminished tactical behavior. Talking on a cellular phone while driving has been shown to impair tactical performance as well.

Strategic performance is the third level and refers to goals such as navigation. Situational awareness is also part of strategic performance. Research suggests that talking on a cellular phone while driving impairs situational awareness. The current study investigates the effect of cellular phone conversations on strategic performance in greater depth.

The research also investigates the root cognitive causes of attention deficits. The researchers do not seek to show whether cellular phone conversations affect driving performance, but rather why they do. Attention allocation is the primary theoretical underpinning of the study. Research has revealed a meaningful difference in performance when the driver speaks with a passenger in the car versus when speaking on the phone. Drivers speaking with passengers often perform better and pay more attention to their surroundings than drivers who are alone. Drivers who are alone and speak on the phone while driving tend to be the most impaired because their attention resources are misallocated.

Finally, the researchers examine theories of conversation. Conversation demands attention resources, but may in some cases enhance situational awareness. The authors refer to the phenomenon of grounding, in which "all parties in a conversation share relevant knowledge, beliefs, and assumptions," as well as "shared visual attention" cues (Drews, Pasupathi & Strayer, 2008, p. 393). Shared awareness theory therefore suggests that drivers with passengers in the car are more likely to be aware of their surroundings than drivers who are alone. Driver and passenger become "mutually engaged" in the act and experience of driving (Drews, Pasupathi & Strayer, 2008, p. 394), with both attending to traffic variables, for example. The content of conversations may also affect the driver's attention, especially when the conversation is held over the phone — in particular, close-call stories are highly likely to impact driving performance. The current research examines whether and why there is a difference between the effects of cellular phone versus passenger conversations on driver performance.

Research Methodology and Study Design

Unlike prior research, the current study uses naturalistic conversations. Prior research has relied on simulated conversations, which are often too artificial to be externally valid. In the current study, 96 participants (48 friend dyads) with valid driver's licenses were tested for vision. Forty-seven participants were female and 49 were male; although ages ranged from 18 to 49, the average age was 20. Informed consent was obtained from all participants.

The authors relied on the PatrolSim driving simulator, which loaded a 24-mile multilane beltway "with on and off ramps, overpasses, and two-lane traffic in each direction" (Drews, Pasupathi & Strayer, 2008, p. 395). An "irregular flow" setting was used, in which other vehicles changed lanes and speeds. The speed limit in the simulation was 65 mph. The simulation was described as cognitively demanding, requiring the driver to "pay attention to the surrounding traffic" (Drews, Pasupathi & Strayer, 2008, p. 395). A familiarization sequence lasting 15 minutes was divided into three parts: rural night driving, downtown driving, and highway daytime driving.

During the familiarization session, one member of each dyad was randomly selected to serve as the conversationalist, and was then assigned either to a passenger or a cellular phone condition (Drews, Pasupathi & Strayer, 2008, p. 395). Speakers were instructed to share a "close call" story that they had not previously shared with the driver.

There were two distinct sections of the experiment: dual-task and single-task. During the dual-task scenario, dyads conversed either in person or over a simulated phone call. During the single-task scenario, there was only driving with no conversation; this served as the control condition. The order of assignments was randomized. In all driving conditions, drivers were given instructions specifying which exit ramp to use. The entire experiment lasted 60 minutes, with individual driving sequences lasting ten minutes for both single-task and dual-task sections.

Measures Used in the Study

Measures encompassed both driving performance and conversation analysis. Driving performance measures addressed operational, tactical, and strategic levels. Operational measures captured "how well participants stayed in the center of the lane without lateral moving or drifting" (Drews, Pasupathi & Strayer, 2008, p. 395). Tactical measures included average speed and average following distance — the distance between the driver and the next car ahead. Strategic performance measures addressed navigational outcomes, such as whether drivers took the correct exit.

Conversations were transcribed and analyzed. Although the close-call story was required, conversations naturally drifted and were analyzed in terms of references to situational variables such as traffic. Turn-taking patterns were also analyzed. Word complexity, measured by the number of syllables per word, was assessed. The demands of the driving environment at specific points during the conversation were also recorded and analyzed.