  In this paper, we introduce a novel conceptual model for a robot's behavioral
adaptation in its long-term interaction with humans, integrating dynamic robot
role adaptation with principles of flow experience from psychology. This
conceptualization introduces a hierarchical interaction objective grounded in
the flow experience, serving as the overarching adaptation goal for the robot.
This objective intertwines both cognitive and affective sub-objectives and
incorporates individual and group-level human factors. The dynamic role
adaptation approach is a cornerstone of our model, highlighting the robot's
ability to fluidly adapt its support roles - from leader to follower - with the
aim of maintaining equilibrium between activity challenge and user skill,
thereby fostering the user's optimal flow experiences. Moreover, this work
delves into a comprehensive exploration of the limitations and potential
applications of our proposed conceptualization. Our model places a particular
emphasis on the multi-person HRI paradigm, a dimension of HRI that is both
under-explored and challenging. In doing so, we aspire to extend the
applicability and relevance of our conceptualization within the HRI field,
contributing to the future development of adaptive social robots capable of
sustaining long-term interactions with humans.
