bioRxiv2026
Human interactions span a range of contexts, from cooperation to competition. Negotiation, in particular, is a complex and extended social process in which individuals must reach mutually acceptable decisions despite conflicting incentives. The neural computations that support strategic behavior in such social dilemmas remain insufficiently understood. Here, we combine cognitive computational modeling, electroencephalography (EEG), functional Magnetic Resonance Imaging (fMRI), and fMRI-guided Transcranial Magnetic Stimulation (TMS) to demonstrate that oscillatory activity anchored in the temporoparietal junction (TPJ) causally shifts social learning during strategic bargaining. We found that TPJ metabolic activity and alpha-band oscillations are associated with the use of a feedback-based learning strategy during bargaining. Causal perturbation with rhythmic alpha-frequency TMS selectively modulates this strategy, increasing endogenous alpha oscillations and shifting behavioral learning parameters. Together, these findings reveal a frequency-specific mechanism within the neural substrates of social cognition that implements adaptive social learning, offering insights into potential neuromodulatory targets for ameliorating social dysfunction in neuropsychiatric conditions. Significance StatementStrategic negotiation requires predicting how others will respond to our actions, yet the neural computations supporting this form of social learning have remained elusive. By integrating computational modeling with EEG, fMRI, and frequency-specific TMS, we identify a mechanistic link between alpha-band activity in the temporoparietal junction (TPJ) and feedback-based learning during social exchange. Trial-by-trial estimates of this learning strategy were tracked by TPJ metabolic and oscillatory signals, and rhythmic alpha TMS causally enhanced both the neural signature and the behavioral expression of this strategy. These findings provide causal evidence for a frequency-specific mechanism within the neural systems that supports adaptive social learning. They also highlight the TPJ-alpha system as a promising target for neuromodulatory interventions to improve social functioning in neuropsychiatric conditions. Key FindingsO_LIModel-based behavioral analyses revealed two distinct strategies during social negotiation: a feedback-based learning mechanism (U-strategy) and a reputation-based updating mechanism (A-strategy). C_LIO_LIBoth strategies robustly predicted participants adaptive behavior across samples and conditions, and their modulation accounted for differences in negotiation outcomes. C_LIO_LIEEG analyses revealed frequency-specific alpha and beta power modulation linked to U-strategy computations during partner anticipation, localized to right temporoparietal regions. C_LIO_LIfMRI analyses revealed that trial-by-trial U-strategy estimates selectively modulated BOLD activity within the temporoparietal network associated with mentalizing. C_LIO_LIRhythmic alpha-frequency TMS over individually localized Theory-of-Mind TPJ sites causally altered negotiation behavior, shifting U-learning parameters toward a more conservative strategy. C_LIO_LITMS-EEG analyses demonstrated that alpha-frequency TMS induced time-locked alpha activity in functionally connected frontal sites, consistent with enhanced anticipatory computations. C_LIO_LITogether, these multimodal findings establish a causal, frequency-specific mechanism in the TPJ that implements social value learning during strategic bargaining. C_LI