The impact of human-robot multimodal communication on mental workload, usability preference, and expectations of robot behavior

Multimodal communication between humans and autonomous robots is essential to enhance effectiveness of human-robot team performance in complex, novel environments, such as in military intelligence, surveillance, and reconnaissance operations in urban settings. It is imperative that a systematic approach be taken to evaluate the factors that each modality contributes to the user's ability to perform successfully and safely. This paper addresses the effects of unidirectional speech and gesture methods of communication on perceived workload, usability preferences, and expectations of robot behavior while commanding a robot teammate to perform a spatial-navigation task. Each type of communication was performed alone or simultaneously. Results reveal that although the speech-alone condition elicited the lowest level of perceived workload, the usability preference and expectations of robot behavior after interacting through each communication condition was the same. Further, workload ratings between the gesture and speech-gesture conditions were similar indicating systems that employ gesture communication could also support speech communication with little to no additional subjectively perceived cognitive burden on the user. Findings also reveal that workload alone should not be used as a sole determining factor of communication preference during system and task evaluation and design. Additionally, perceived workload did not seem to negatively impact the level of expectations regarding the robot's behavior. Recommendations for future human-robot communication evaluation are provided.