Laboratory studies have shown that ecological interfaces can enhance operator performance in process control. However, limited verification and validation studies in representative settings are impeding the adoption of the Ecological Interface Design (EID) framework in the nuclear domain. A companion article presents an application of EID to the secondary side of a boiling water reactor plant simulator, demonstrating that the framework can lead to display features and verification criteria relevant to supporting operators in both anticipated and unanticipated situations. This article presents an empirical study as a first step towards the validation of EID in the nuclear domain. The results suggest that ecological displays have a marked advantage in supporting operator performance during monitoring for unanticipated events as compared to mimic-based displays. The ecological displays did not support operator performance differently for other types of tasks. This study provides supporting or validation evidence that EID is effective at a scale and level of complexity that is representative of nuclear power plant operations. The implications for introducing ecological displays into NPP control rooms are discussed.