Modelling visual-vestibular integration and behavioural adaptation in the driving simulator

To test hypothesised mechanisms behind driver response to down-scaled motion cues in simulators, a driver steering model was developed, by extending an existing modelling framework with models of multisensory integration and behavioural adaptation. In a slalom task, the model robustly reproduced several empirical findings : Removing motion cues initially resulted in decreased task performance and increased steering effort, but after behavioural adaptations, performance improved and steering effort went down. Unexpectedly, the model also reproduced another empirical finding : Optimal path-tracking for an intermediate motion scaling, smaller than unity. Overall, together with the existing empirical findings, the simulation results suggest that : (1) Drivers make direct use of vestibular inputs as part of determining appropriate steering input, and (2) motion down-scaling causes drivers to behave as if they are underestimating the vehicle’s rate of rotation. However, (3) in the slalom task, a certain degree of such underestimation brings a path-tracking performance benefit. Furthermore, (4) behavioural adaptation, as empirically observed, may occur in the form of (a) down-weighting of vestibular cues, and/or (b) increased sensitivity to control errors, in determining when to adjust steering and by how much, but (c) seemingly not in the form of a full compensatory reinterpretation of the down-scaled vestibular input