Investigating users’ mental representation of likelihood alarm systems with different thresholds

ABSTRACT

This study investigated effects of threshold setting in likelihood alarm systems (LASs) on safety, performance and participants’ mental representation of LASs. Three LASs were compared under two workload conditions. LASs had the same lower (first) threshold separating non-alerts from warnings but differed with regard to their higher (second) threshold dividing warnings from alarms. Behaviour, performance and trust were assessed. Participants of all three conditions responded to almost every alarm but only to parts of the warnings. Threshold setting affected safety, as the most liberal second threshold led to the highest joint human–machine sensitivity. Increasing workload decreased concurrent task performance. A negative correlation of trust in warnings and response rates to warnings reflected reliance and implies a mental representation of graduation of non-alerts. Results suggest that LAS threshold setting allows a precise guidance of users’ behaviour and show the importance of knowledge regarding users’ mental representation for the design of LASs.

KEYWORDS:

• Graded warnings
• trust
• compliance and reliance
• decision-making
• signal detection theory

Acknowledgments

I thank Dietrich Manzey for his recommendations regarding the manuscript. I thank Marcus Bleil for the support with the research environment and I thank Mandy Dotzauer and Frank Bolton for proofreading.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) [grant number GRK 1013].

Notes on contributors

Rebecca Wiczorek

Rebecca Wiczorek works as the leader of a junior research group at the Department of Psychology and Ergonomics at the Technische Universität Berlin. She holds a Ph.D. in human factors obtained from the Technische Universität Berlin in Germany in 2012.