Developing a sense of agency scale for heavy machinery operation

Sense of agency (SoA) has long been a focus area in the field of human-machine interactions, because it is thought to relate to progress and improvements in developing interface systems that users can control with intention. However, there is currently no systematic SoA evaluation method within the context of heavy machinery operation. With our research, we intended to develop a SoA scale for heavy machinery operation (SoAS-HMO). The scale evaluated the psychological experiences of operators while they voluntarily operated heavy machinery. To build this scale, we conducted two surveys: a semi-structured interview survey to initially prepare the scale items, and a questionnaire survey to explore and confirm the scale structure. Subsequent factor analysis revealed one factor and twenty-one items that were related to the SoA experienced during operation, with sufficient reliability and validity, specifically with goodness of fit index (GFI) = 0.933, adjusted GFI (AGFI) = 0.911, comparative fit index (CFI) = 0.909., and Cronbach's a = 0.97. Therefore., this scale can successfully measure the subjective SoA of the operator and be applied to evaluate machinery efficiency. Our study provides progress towards improving heavy machinery systems that can be intentionally controlled by operators.