Consumer automation is a suitable venue for studying the efficacy of untested humanness design methods for promoting specific trust in multi-component systems. Subjective (trust, self-confidence) and behavioural (use, manual override) measures were recorded as 82 participants interacted with a four-component automation-bearing system in a simulated smart home task for two experimental blocks. During the first block all components were perfectly reliable (100%). During the second block, one component became unreliable (60%). Participants interacted with a system containing either a single or four simulated voice assistants. In the single-assistant condition, the unreliable component resulted in trust changes for every component. In the four-assistant condition, trust decreased for only the unreliable component. Across agent-number conditions, use decreased between blocks for only the unreliable component. Self-confidence and overrides exhibited ceiling and floor effects, respectively. Our findings provide the first evidence of effectively using humanness design to enhance component-specific trust in consumer systems.Practitioner summary: Participants interacted with simulated smart-home multi-component systems that contained one or four voiced assistants. In the single-voice condition, one component's decreasing reliability coincided with trust changes for all components. In the four-voice condition, trust decreased for only the decreasingly reliable component. The number of voices did not influence use strategies.Abbreviations: ACC: adaptive cruise control; CST: component-specific trust; SWT: system-wide trust; UAV: unmanned aerial vehicle; CPRS: complacency potential rating scale; MANOVA: multivariate analysis of variance.
Keywords: Human-machine systems; human-automation interaction; humanness; trust in automation.