Scientists Watch Brains Negotiate in Real Time as New Paradigm Rewrites Social Neuroscience

For decades, scientists studying how people cooperate and compete have relied on a strangely artificial setup: two strangers seated at separate screens, clicking buttons in isolated rounds of the Prisoner’s Dilemma or the Ultimatum Game. A new opinion article published in Frontiers in Systems Neuroscience argues that this turn-based approach has reached its limits, and it points to a groundbreaking experimental paradigm as the way forward. The article, led by Qiang Li of Guizhou Education University, examines the continuous Cooperation-Competition Foraging (CCF) Game introduced by Lewen and colleagues in Communications Psychology, a paradigm designed to capture how cooperation and competition emerge dynamically in continuous time and space during real social interactions.

The most significant contribution of the CCF work lies in its shift from discrete, symbolic frameworks to a continuous, embodied, interactive perspective grounded in dynamical systems theory. In traditional paradigms, participants typically make binary or limited-choice decisions in discrete trials where decision-making and action are temporally separated, and there is a lack of real-time visible behavioral cues. Although such setups are conducive to modeling, they are limited in ecological validity and fail to capture the continuous flow of information, bodily coordination, and real-time strategic adjustments inherent in real-world social interactions. In contrast, the CCF paradigm enabled participants to express their strategies through continuous movement trajectories and adjust their behavior on a millisecond scale based on the actions of their partner, thus embodying the concept of decide-while-acting.

At the center of the paradigm is a large transparent bidirectional display positioned between two participants seated face-to-face, such that the game unfolds on the screen while each participant can simultaneously see the other through it. This arrangement is far more demanding and resource-intensive than conventional computer-based social decision-making paradigms, but precisely for that reason it represents a remarkable methodological commitment to ecological validity. Rather than reducing social choice to isolated responses on separate screens, the design preserves a critical feature of real-world interaction: people make decisions while continuously monitoring one another’s facial expressions, body posture, movement tendencies, and moment-to-moment behavioral adjustments. As a result, participants can modify their own choices online in light of the partner’s visible reactions, making the unfolding decision process much closer to how cooperation and competition operate in everyday social life.

Beyond the ingenuity of the apparatus itself, a second and equally important advantage is that the interaction remains continuously structured and behaviorally informative throughout the task. The game unfolds in a shared two-dimensional space in which both agents, all targets, and the evolving payoff structure are visible to both participants at all times. Crucially, the task preserves continuity from one moment to the next: after a target is collected, new targets appear without resetting the positions of the agents or the remaining items, so the shared spatial situation continues to evolve rather than restarting from scratch. This absence of clearly demarcated trial boundaries is methodologically important, because it allows interaction history to accumulate and shape subsequent decisions. Participants do not repeatedly return to a neutral starting point; instead, each new movement and choice is made against the background of prior coordination, hesitation, concession, or defection. In this way, strategy formation becomes path-dependent, making it possible to observe how cooperative tendencies are built up, stabilized, disrupted, or repaired over time.

The target and payoff structure is another particularly insightful feature of the design. At every moment, participants faced one single target worth 7 cents to one player alone and two joint targets that required cooperation but distributed payoffs asymmetrically as 5/2 and 2/5. This is an elegant solution because the total joint payoff of the cooperative and non-cooperative options is held constant, avoiding a trivial incentive bias toward either target type, while the asymmetry within the cooperative options creates the conditions under which one participant can accept a less favorable immediate outcome for the partner’s benefit. In turn, this makes prosocial intent behaviorally legible and allows the study to capture whether such short-term concessions are later reciprocated, thereby revealing how reciprocal cooperation can be established and maintained over repeated interactions.

Notably, Lewen and colleagues demonstrated that dyads spontaneously converge toward relatively stable set-points along a cooperation-competition spectrum, forming cooperative, intermediate, and competitive groups. Rather than adopting extreme strategies, most dyads stabilized around intermediate patterns. Through computational modeling, the authors showed that weighted path minimization, combined with across-cycle predictors such as invitations and target history, predicted dyadic choices with high accuracy of 87 percent. These findings suggest that social coordination emerges from a dynamic interplay between low-level sensorimotor coupling and higher-order strategic preferences. The authors also showed that model-derived choice uncertainty is systematically related to subsequent trajectory structure: higher uncertainty is associated with more curved trajectories, miscoordination, and target divergence, whereas invitations reduce uncertainty and promote efficient coordination.

For social neuroscience, the paradigm is equally important because it renders social decision-making tractable not merely as a final choice outcome, but as a temporally extended process composed of transient interaction events and ongoing decision dynamics that can be related to neural activity. In standard economic games, neural activity is typically aligned to coarse markers such as stimulus onset, button press, or feedback. By contrast, the present paradigm identifies fine-grained social events within continuous interaction, including invitations to cooperate, failed invitations, leader-follower episodes, concurrent approaches to the same target, movement-based hesitation or redirection, and overt breakdowns of coordination in which the two agents commit to different targets. This feature opens the door to asking more specific neural questions: which brain signals accompany a costly cooperative overture, the acceptance or rejection of an invitation, a competitive race for a single target, or a sudden departure from an emerging cooperative convention? In that sense, the paradigm could allow neuroscience to move beyond broad contrasts such as cooperation versus competition toward the neural signatures of socially meaningful micro-events that constitute those broader states.

Integrating the CCF paradigm with social neuroscience requires asking which aspects of the task different neural methods are best suited to capture. Because the paradigm combines rapid event-related transitions, continuous interpersonal adjustment, and slower strategic structure unfolding across repeated collection cycles, it offers a useful bridge between multiple levels of neural analysis. Electroencephalography, magnetoencephalography, and, where clinically available, electrocorticography are particularly attractive for tracking how participants use the partner’s trajectory and positioning in the shared action space to commit, revise, coordinate, or compete in real time. Functional near-infrared spectroscopy should be positioned somewhat differently. Relative to EEG, MEG, and ECoG, fNIRS is not optimal for resolving millisecond-scale neural events, because it indexes slower hemodynamic changes rather than direct electrophysiological activity. Its value in this paradigm lies instead in its ability to track superficial cortical dynamics at a coarser but still informative spatiotemporal scale, making it suitable for processes that evolve over seconds within and across collection cycles, such as stable cooperative-competitive set points, across-cycle history effects, invitation-based coordination, and the maintenance of established cooperation.

The CCF paradigm could also provide a useful platform for hyperscanning, an approach that is gaining momentum in social neuroscience. Because social interaction is inherently bidirectional and dynamically reciprocal, hyperscanning is particularly well suited to this kind of paradigm, as it enables the simultaneous recording of neural activity from both interacting partners and permits the investigation of neural processes not only within individuals but also between them. Future hyperscanning studies could therefore ask whether inter-brain coupling strengthens when partners converge on a shared decision and weakens when invitations fail, coordination breaks down, or competing trajectories emerge. fMRI should also be considered a promising extension, even though its temporal resolution is less naturally suited to the task’s rapid event structure. Its main value would likely lie in using its comparatively high spatial resolution to identify the distributed neural systems that support slower and more integrated aspects of performance, including stable strategic tendencies, the valuation of cooperation relative to individual payoff, and the representation of latent social variables that guide joint behavior over time. One promising future direction may be multimodal integration. EEG-fMRI, for example, could potentially capitalize on the relatively high temporal resolution of EEG and the relatively high spatial resolution of fMRI to relate rapid event-locked signatures of invitation, uncertainty reduction, or movement commitment to the cortical and subcortical systems involved in maintaining broader strategic context.

Yet this analysis also exposes a critical interpretive problem: in a task where partners often move at similar times and along related trajectories, apparent inter-brain coupling may partly arise from shared sensorimotor demands rather than genuine social interaction. For this reason, neural effects should be evaluated while accounting for key motor variables, including movement velocity, trajectory curvature, and reaction-time asymmetry. However, in the interactive task, movement is not merely an external nuisance variable superimposed on a social process; it is one of the primary channels through which social information is generated and exchanged. Participants communicate commitment, hesitation, adaptation, and competition through the timing and geometry of their actions. Motor and social processes are therefore often intrinsically intertwined, making it difficult to determine whether shared neural structure reflects common kinematics, social coordination, or both. Beyond laboratory dyads, the CCF paradigm offers a flexible platform for examining how social relationships modulate continuous cooperation-competition dynamics. Comparing romantic partners, strangers, or hierarchical dyads could reveal how relational priors shape strategy stabilization and inter-brain coupling regimes. Similarly, extending this framework to clinical populations such as autism spectrum conditions or social anxiety may reveal whether atypical social functioning reflects altered stability of interpersonal attractor states, reduced invitation sensitivity, or disrupted neural coupling transitions. For these reasons, the CCF paradigm should be regarded as an important step toward an interaction-level science of social decision-making. Rather than treating cooperation and competition as fixed properties of isolated individuals, it encourages a shift toward understanding them as dynamically organized states emerging between interacting agents. The broader promise of this work lies not simply in improving the measurement of dyadic outcomes, but in helping explain how shared behavioral states are continuously formed, maintained, and transformed in real time.

Subject of Research: Beyond discrete social decisions: toward continuous dyadic neural dynamics in cooperation and competition

Article Title: Beyond discrete social decisions: toward continuous dyadic neural dynamics in cooperation and competition

Article References: Li, Q., He, J., Li, Z., Rao, C., Luo, J., & Wu, J. (2026). Beyond discrete social decisions: toward continuous dyadic neural dynamics in cooperation and competition. Frontiers in Systems Neuroscience, 20, Article 1809977. https://doi.org/10.3389/fnsys.2026.1809977

Image Credits: AI Generated

DOI: 10.3389/fnsys.2026.1809977

Keywords: Beyond, discrete, social, decisions, toward, continuous, dyadic, neural, dynamics, cooperation, competition, scientific research