Loss of situational awareness due to increased cognitive load is one of the areas considered at the AgeLab in our assessments of factors that impact driver safety. Recent findings have shown that though a driver may have his eyes on the road, his mind may be elsewhere. This lack of attention can be represented by a narrowing of vision (less visual scanning) accompanied by a slower response to incidents. To better quantify the amount of cognitive load that causes changes in driver performance, the AgeLab has developed a Delayed Digit Recall task (n-back).
The Delayed Digit Recall n-back task is a calibration method that systematically increases the cognitive demand placed on an individual. The lab has used this task in a series of studies. The most recent publication on this work is now available on-line. Titled, A Field Study on the Impact of Variations in Short-Term Memory Demand on Drivers’ Visual Attention and Driving Performance across Three Age Groups, this paper provides evidence of horizontal gaze concentration (a decrease in dispersion of gaze) with increased cognitive demand. Gaze restriction was evident during the least demanding level of the task and showed further restriction at the two higher levels of demand.
A companion paper, Sensitivity of Physiological Measures for Detecting Systematic Variations in Cognitive Demand from a Working Memory Task: An On-Road Study across Three Age Groups, has also been accepted for publication. In this work, both heart rate and skin conductance level (sweat gland activity) were found to increase in a relatively linear manner with demand. This is significant in that it demonstrates that physiological measures can be used to objectively monitor cognitive workload in the driving environment. Both papers are to appear in Human Factors: The Journal of the Human Factors and Ergonomics Society.
Paying attention to the road is not a binary operation; drivers can give varying degrees of attention to the task at hand. To simulate this, 0, 1 and 2-back tasks model increasing levels of cognitive load, which in turn result in decreased attention to scanning the roadway. This is intended to model in an objective manner what an individual may experience while, for example, having a phone conversation – even if the phone call is hands-free. An AgeLab White Paper, available here, introduces and explains the Delayed Digit Recall n-back task in detail. It is important to note that among the relatively healthy people studied, age was not found to change the basic pattern of effects observed with increased cognitive demand.
The Delayed Digit Recall n-back task is currently being used in the International Standard Organization’s (ISO) TC22/SC13/WG 8 project, Coordinated studies on the Detection Response Task (DRT), as a surrogate for cognitive demand. Studies are taking place in Germany, France, Sweden, Canada, China and the United States. Earlier work with Delayed Digit Recall task following the protocol developed at the AgeLab was performed in Korea. In a U.S. Department of Transportation - National Highway Safety Administration document, Developing a Test to Measure Distraction Potential of In-Vehicle information System Tasks in Production Vehicles, the 2-back condition of the task was suggested as a “starting point for setting a limit for acceptable ‘dose’ of cognitive distraction.”