In robotics, understanding human interaction with autonomous systems is crucial for enhancing collaborative technologies. We focus on human-swarm interaction (HSI), exploring how active robot groups of varying sizes affect operators’ cognitive and perceptual reactions over distinct durations. We analyze the impact of different numbers of active robots within a 15-robot swarm on operators’ time perception, emotional state, flow experience, and task difficulty perception. Our findings indicate that managing multiple active robots when compared to one active robot significantly alters time perception and flow experience, leading to a faster passage of time and increased flow. More active robots and extended durations cause increased emotional arousal and perceived task difficulty, highlighting the interaction between the number of active robots and human cognitive processes. These insights inform the creation of intuitive human-swarm interfaces and aid in developing swarm robotic systems aligned with human cognitive structures, enhancing human-robot collaboration.

Many large-scale multi-robot systems require human input during operation in different applications. To still minimize the human effort, interaction is intermittent or restricted to a subset of robots. Despite this reduced demand for human interaction, the mental load and stress can be challenging for the human operator. A specific effect of human-swarm interaction may be a hypothesized change of subjective time perception in the human operator. In a series of simple human-swarm interaction experiments with robot swarms of up to 15 physical robots, we study whether human operators have altered time perception due to the number of controlled robots or robot speeds. Using data gathered by questionnaires, we found that increased swarm size shrinks perceived time and decreased robot speeds expand the perceived time. We introduce the concept of subjective time perception to human-swarm interaction. Future research will enable swarm systems to autonomously modulate subjective timing to ease the job of human operators.