Abstract: In human societies, competition and cooperation are not mutually exclusive phenomena but are instead deeply interdependent and dynamically intertwined. As global resource pressures continue to intensify, social comparisons among individuals play a pivotal role in shaping tendencies toward competition and cooperation, influencing the emergence, regulation, and transformation of co-opetition behaviors across multiple dimensions. While co-opetition has traditionally been conceptualized at the intergroup level, the ways in which these behaviors manifest and evolve dynamically at the interpersonal level remain inadequately understood, thereby highlighting a critical gap in current research.
In this article, we first provide a comprehensive review of the relationship between competition and cooperation in interpersonal interactions and subsequently introduce an innovative two-dimensional dynamic model of interpersonal co-opetition. Unlike conventional approaches that conceptualize competition and cooperation as opposing ends of a single continuum, this model treats them as two independent dimensions, thereby establishing “co-opetition” as a distinct and central behavioral state. The model incorporates “social comparison” and “goal alignment” as key driving factors, illustrating how stable personality traits interact with situational and contextual variables to produce dynamic transitions among behavioral states, including cooperation, competition, co-opetition, and avoidance. This framework extends traditional social value orientation theories by emphasizing the importance of bidirectional motivational forces in shaping sequential decision-making processes across context-specific scenarios. It also aligns with evolutionary perspectives suggesting that competition and cooperation are adaptive strategies dynamically adjusted in response to relative payoffs and social cues.
Building upon commonly used experimental paradigms for examining co-opetition, this article introduces the “Share Game” paradigm. In this design, participants allocate a fixed pool of resources according to their individual investment proportions. The paradigm generates dual motivational forces: on the one hand, individuals are incentivized to increase their investment to secure a larger share of resources, reflecting competitive tendencies; on the other hand, intrinsic constraints encourage participants to limit excessive competition and minimize resource wastage. Within this paradigm, interpersonal co-opetition behaviors can be quantified across multiple dimensions. First, investment levels are classified relative to the Nash equilibrium and the median strategy, distinguishing cooperation, co-opetition, competition, and extreme behaviors such as over-competition or zero investment. Second, social comparison is operationalized through the relative differences between individual and opponent outcomes, and further supplemented by real-time assessments of emotional valence and arousal. Third, goal alignment is evaluated by comparing the average investments of both parties to the median strategy, indicating the degree of shared objectives. Finally, dynamic variations in sequential decision-making facilitate the disentanglement of two underlying psychological mechanisms: consensus-based regulation and avoidance-driven restraint at the individual level.
The study also examines the neural mechanisms underlying the effects of social comparison on co-opetition behavior. Future research is encouraged to integrate neuroimaging techniques with computational modeling. In particular, reinforcement learning approaches can be combined with social comparison metrics, such as upward and downward comparisons, as well as counterfactual reasoning. Such integrative approaches are expected to systematically reveal the computational neural mechanisms that govern interpersonal co-opetition decisions.
In conclusion, this study provides systematic empirical support for a two-dimensional dynamic model of interpersonal co-opetition, demonstrating that competition and cooperation are not mutually exclusive but can coexist dynamically within individuals. By incorporating social comparison and goal alignment as core driving factors, the model reveals how stable personality traits interact with situational variables to produce dynamic transitions among cooperation, competition, co-opetition, and avoidance behaviors. The “Share Game” paradigm enables the quantification of co-opetition across multiple behavioral and psychological dimensions, offering a flexible and practical tool for experimental investigation. Furthermore, by integrating evidence from behavioral experiments, computational modeling, and neuroimaging, the study elucidates the neural and cognitive mechanisms underlying interpersonal co-opetition decision-making. This research offers a novel theoretical perspective on how individuals navigate trade-offs in complex social environments and points to three primary directions for future inquiry. First, future studies could investigate the influence of trait differences, such as social comparison tendencies and goal alignment preferences, on co-opetition behavior. Second, experimental paradigms with higher ecological validity could be developed to construct computational models that integrate multidimensional parameters. Third, combining neuroimaging with reinforcement learning, social comparison, and counterfactual reasoning could systematically reveal the computational neural mechanisms underlying co-opetition behaviors.

Key words: social cognition, cooperation, competition, social comparison