The influence of incentives and instructions on behaviour in driving simulator studies

Abstract There are a number of factors which may influence the validity of experimental studies, including the incentives offered and the instructions provided to participants. These have been little-studied in the driving domain. The aim of this study was to investigate how manipulating these factors influenced participants’ feelings of ‘presence’ (i.e. the extent to which they believed they were actually driving and not in a simulated environment). The findings showed that imposing a penalty system for poor driving performance and providing ‘good driving’ instructions did not significantly affect presence ratings. This has a number of plausible explanations, including research study participants’ inherent need to perform well under test conditions and the small range of performance variability expected in a normal driving scenario. The financial penalty resulted in slightly slower speeds, although none of the participants drove excessively quickly, supporting the argument that study participants tend to perform diligently under test conditions irrespective of incentives or instructions. Participants in the penalty and instructions conditions gave higher ratings for negative effects (related to physically feeling unwell), suggesting that these conditions made them more aware of the physical symptoms of being in a simulator (but not that participants were actually experiencing more sickness). The results can be viewed positively in terms of reliability and generalizability across different driving simulator studies, as variations in study design (i.e. how instructions are delivered to participants and whether participants are paid to participate) do not have a significant effect on performance.