Stimulus-Response Compatibilitiy Effects for Warning Signals and Steering Responses

Stimulus-response compatibility is relevant to the way a collision avoidance system signals a hazard. Using the location of a warning tone as the signal, standard spatial compatibility effects predict that it would be most beneficial to have the tone correspond to the desired response direction. However, because drivers typically turn away from sounds created by hazards, they may adopt a frame of reference where turning away from the warning tone is more compatible than responding toward it. This issue was examined in an experiment in which subjects responded to tones in the left or right ear by turning a steering wheel clockwise or counterclockwise, with the meaning of the tones manipulated to simulate warning signals. Two groups received typical compatibility instructions (tone instructions), and two received instructions specifying that the tone was a warning signal (warning instructions) indicating either the location of the danger (from which they were to turn away) or the escape direction (toward which they were to turn). The compatibility effect was in the same direction and of the same magnitude for both the warning instructions and the tone instructions. This outcome implies that instructions to turn away from danger did not cause subjects to adopt an avoidance frame of reference and that spatial correspondence was the overriding factor. The results suggest that collision avoidance systems should signal the escape direction, but these results need to be verified in simulated and actual driving conditions.