Handbook of Driving Simulation for Engineering, Medicine, and Psychology

Psychological Fidelity: Perception of Risk

Author
Thomas A. Ranney, Transportation Research Center Inc.

Abstract
The Problem. High-fidelity driving simulators provide a realistic and compelling experience for research participants. However, the credibility of research results from simulator studies continues to be challenged. The fidelity of the driving experience appears insufficient to overcome criticisms concerning the lack of psychological fidelity, defined as the extent to which the risks and rewards of participation in the experiment correspond to real-world risks and rewards. Key Results of Driving Simulator Studies. Experimental studies eliminate the injury risk associated with driving. They also typically eliminate the trip purpose, which influences all components of real-world driving. Unfortunately, researchers typically give little consideration to this problem, often instructing participants to drive as they normally would. In the absence of a well-defined driving context, such instructions can be confusing to some participants. Tools Available to Researchers. Well-designed driving simulator experiments eliminate confusion about driving motives by creating constrained situations to elicit specific behaviors. Researchers must identify the driving components that have been eliminated by the simulation and attempt to replace them through the use of instructions and performance incentives. Instructions define the performance space and driving task components; incentives define the relative priorities associated with the task components. The effects of incentives on performance are determined by some combination of (1) the nature of the incentive; (2) task characteristics; (3) aspects of performance selected for measurement; and (4) individual differences. Incentives are likely to improve certain aspects of performance, while degrading others at the same time, implying that care must be taken in matching incentives to performance measures. Scenarios and Dependent Variables. Reward/penalty schemes are used to incorporate performance incentives into driving simulator studies. Practical issues associated with their use include: simulating the effects of significant negative outcomes (i.e., crashes); multiple crashes; effects of incentives over time; assessment of reward/penalty systems; and non-independence of performance measures. Detailed examples of the use of reward/penalty systems are presented. Platform Specificity and Equipment Limitations. Problems of psychological fidelity apply to all platforms. Improving psychological fidelity eliminates unwanted variability due to individual differences in driving, which result from uncertainty about the experimenter’s priorities.

Keywords
Psychological Fidelity, Driver’s Motives, Risk Perception, Performance Incentives, Instructions, Rewards and Penalties

Key Points
• Driving simulator studies continue to be criticized for lack of realism, despite significant advancements in the fidelity of the driving experience.
• Some amount of artificiality is inherent in all experiments that use driving simulators. An often-overlooked component of this artificiality is psychological fidelity, defined here as the extent to which the risks and rewards of participation in the experiment correspond to real-world risks and rewards.
• Experimental studies typically eliminate the trip purpose, which influences all components of real-world driving. Researchers must therefore provide direct guidance to participants concerning their expectations about the simulated trip.
• Failure to define the driving context is likely to result in a significant amount of unwanted variability in performance measures, reflecting a combination of confusion and different assumptions made by participants about the priorities in the experiment.
• Instructions and performance incentives are the main tools available to researchers for improving psychological fidelity of their experiments. Instructions define the performance space; incentives provide guidance about priorities.
• Reward/penalty systems can be used to represent the real-world tradeoff between the desire for safe and timely arrival and the desire to avoid speeding tickets and crashes. Their credibility would be increased if researchers would incorporate reward/penalty system components as independent variables in experimental designs and examine their effects on driving behavior.
• Institutional Review Boards, responsible for ensuring the safe and ethical treatment of human participants in research studies, will typically impose limits on researchers’ use of performance incentives and penalties. Excessive rewards (e.g., completion bonuses) may be considered coercive while limits on penalties make it virtually impossible to accurately simulate the significant negative consequences associated with crash involvement.

Key Readings
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