Ultimatum Game

Background

The Ultimatum Game is a classic socio-economic game about the allocation of monetary resources to study prosocial behavior and the relationship of self-interest and perception of fairness. In the Ultimatum Game participants get the choice to share money with another person but the respondent has the ability to reject the offer which results in a zero payoff for both parties. Findings consistenly show low offers (below 30% of the total) are rejected to punish 'unfair' treatments even at personal costs. These results challenge the traditional view in Economics theory that people would always try to maximize payoffs ("Homo economicus": even a little is better than none at all).

Werner Güth and colleagues spearheaded the field of behavioral economics by introducing the Ultimatum Game in 1982, providing an experimental framework for the systematic study of human behavior resource allocation scenarios. The Dictator Game joined the field in 1986. In contrast to the Ultimatum Game, respondents in the Dictator Game don't get the choice to reject the offers, thus removing the no-payoff threat to the proposer which helps isolate altruism from strategic "fairness".

The Millisecond Ultimatum Game is based on the published design by Katia Harle´and Alan Sanfey from 2010 who focused on the role that incidental emotions (such as feeling sadness due to reasons unrelated to the monetary transaction in the Ultimatum Game) have on participants' rejection behavior of unfair sharing behavior. Their findings demonstrate that emotions unrelated to the immediate economic situation can influence social-economic choices by affecting sensitivity to fairness. While Harle´ and Sanfey were primarly interested in responder behavior, the Millisecond Ultimatum Game can be played as both, Responder and Recipient. The default game setting assigns the 'Responder' role to participants.

Task Procedure

Instructions tell participants that they are to play several money games (16 in total) with people from other universities, and that they can all win real money. The game rules are explained to them, and before each new game, the roles (Proposer vs. Responder) are assigned. An optional picture of the player can be presented (optional game setting).

Responder Game

After a short wait period in which the Proposer 'prepares' the proposol, the proposal is presented. The participant has 10s (default) to decide to accept the offer (press button 'Accept') or reject it (press button 'Reject'). The script is programmed in such a way that a 'no response' during the 10s period is counted as a rejection. The trial finishes with a screen that shows the outcome (Accepted/Rejected) of the proposal and updates the participant's total.

Proposer Game

The participant has 10s to prepare the proposal. The computer then gets to decide to accept or reject the offer (several options are available for test administrators to select upfront how fair a proposal has to be to be accepted). The trial finishes with a screen that shows the outcome (Accepted/Rejected) of the proposal and updates the participant's total.

What it Measures

The Ultimatum Game is a measure of an individual's sense of fairness and equity preference

Psychological domains

• Social Norms: The unwritten, informal rules that define what is considered acceptable within a specific group
• Self-Interest: The drive to maximize one's own gains, even at the expense of others or regardless of social consequences
• Fairness: A preference for equitable outcomes, even over pure financial gains.

Main Performance Metrics

• Minimum Accepted: The minimum accepted offer by participant in responder role (rejection 'threshold')
• Median Proposal: The median proposed offer by participant in proposer role
• Proposal Range: The minimum and maximum proposal offers by participant in proposer role

Psychiatric Conditions

Research has identified significant behavior differences in the following groups when tested with the Ultimatum Game:

• Schizophrenia
• Major Depression (MDD)
• Borderline Personality Disorder (BPD)
• Psychopathy
• Autism Spectrum Disorder (ASD)
• Frontotemporal Dementia

References

Search Google Scholar for peer-reviewed, published research using the Inquisit Ultimatum Game.

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Güth, W., Schmittberger, R., & Schwarze, B. (January 01, 1982). An experimental analysis of ultimatum bargaining. Journal of Economic Behavior and Organization, 3, 4, 367-388.

Larrick, R. P., & Blount, S. (April 01, 1997). The claiming effect: Why players are more generous in social dilemmas than in ultimatum games. Journal of Personality and Social Psychology, 72, 4, 810-825.

Harlé, K. M., & Sanfey, A. G. (November 01, 2007). Incidental sadness biases social economic decisions in the Ultimatum Game. Emotion, 7, 4, 876-881.

Harle, K.M. & Sanfey, A.G. (2010). Effects of approach and withdrawal motivation on interactive economic decisions. Cognition & Emotion, 24, 1456-1465.

Asp, E., Ramchandran, K., & Tranel, D. (July 01, 2012). Authoritarianism, religious fundamentalism, and the human prefrontal cortex. Neuropsychology, 26, 4, 414-421.

Civai, C., Crescentini, C., Rustichini, A., & Rumiati, R. I. (January 01, 2012). Equality versus self-interest in the brain: differential roles of anterior insula and medial prefrontal cortex. Neuroimage, 62, 1, 102-12.

Weiland, S., Hewig, J., Hecht, H., Mussel, P., & Miltner, W. H. (January 01, 2012). Neural correlates of fair behavior in interpersonal bargaining. Social Neuroscience, 7, 5, 537-51.