Related Experiment Video
Updated: Mar 6, 2026

Combining Behavioral Endocrinology and Experimental Economics: Testosterone and Social Decision Making
Published on: March 2, 2011
Processing of fair and unfair offers in the ultimatum game under social observation
Jutta Peterburs1, Rolf Voegler1, Roman Liepelt2,3
1Institute of Medical Psychology and Systems Neuroscience, University of Münster, Von-Esmarch-Str. 52, 48149 Münster, Germany.
Abstract:
Social context influences social decisions and outcome processing, partially depending on inter-individual differences. The present study investigated social context-dependent modulation of behavior and feedback processing in the ultimatum game (UG) in relation to inter-individual differences in social anxiety. Thirty-two healthy adults completed the UG both under social observation and without observation. Offers were allegedly either randomly generated by the computer or drawn from a pool of offers from previous human players. Overall, fewer unfair than fair offers were accepted. Observation decreased acceptance rates for unfair offers. The feedback-locked feedback-related negativity (FRN) but not the P3 was modulated by observation and fairness, with stronger differential coding of unfair/fair under observation. This effect was strongly correlated with individual levels of social anxiety, with higher levels associated with stronger differential fairness coding in the FRN under observation. Behavioral findings support negative reciprocity in the UG, suggesting that (implicit) social norms overwrite explicit task instructions even in the absence of (alleged) social interaction. Observation enhances this effect. Fairness coding in the FRN was modulated by observation as a function of social anxiety, supporting the notion that altered sensitivity to equality in a social context may contribute to social avoidance in socially anxious individuals.
Related Concept Videos
Naturalistic Observations
Actor-Observer Effect
Social Foundations of Self II: The Generalized Other
Social Foundations of Self I: Play and Game
The Stanford Prison Experiment
Bystander Effect

