In joint human-automation systems, operators must often supervise the automation and adapt their reliance on it based on judgments of its context-specific reliability. For this to occur, operators should trust the automation appropriately. In the design of a water monitoring decision aid's display, Ecological Interface Design was used to satisfy design guidelines for supporting appropriate trust. Design focused upon a visualization that made the aid's use of the DempsterShafer theory directly perceptible. The display was evaluated using a signal detection theorybased approach that measured reliance on automation. Results indicated that the ecological display yielded less appropriate reliance and poorer performance than a conventional display for a highly reliable decision aid. However, the experimental task prevented participants from adapting to the aid's context-specific reliabilities, reducing the validity of the findings. A subsequent study is proposed to further study the effects of ecological displays on automation reliance.iii