Evolution of cooperation: Emotion as a commitment device
In the ultimatum game two players divide a sum of money among themselves. The first proposes a deal (50:50, 80:20) and the second accepts or rejects said deal. If he rejects, neither gets the money. The ultimatum game is a staple of game theory because it reliably shows that people behave irrationally (or not self-regarding) by rejecting unfair deals. Common explanations for that behaviour include social norms of inequity aversion and reciprocity.
Yamagishi et al. (2009) published a paper in PNAS using variants of the ultimatum game to provide support for the emotion as a commitment device explanation. They found that a good third of the players rejected unfair offers even when that implied that only they lost their share and even when the proposer did not know they could decline their share. This is at odds with the explanations above.
According to the researchers the variance in methods (imagined, “real” and faked interaction) and the avoidance of deception enhance the findings’ appeal, but in us it invoked some doubt.Instead they should have used one solid design, namely one-shot games with a fictitious opponent. This way they'd could randomly vary the offered share.
Especially because Bolton & Zwick (1995) found exactly the opposite---players behaved rationally if the first player couldn’t be punished---any difference to their design should have been highlighted. Yamagishi and colleagues argue for emphasising the choice aspect of the game in the instruction, but they don’t mention going to great lengths to eliminate demand characteristics, especially experimenter-subject anonymity. Bolton & Zwick did.
Demand characteristics are well-researched phenomena in psychology and Orne (1962) makes for a nice illustration:
"A number of casual acquaintances were asked whether they would do the experimenter a favor; on their acquiescence, they were asked to perform five push-ups. Their response tended to be amazement, incredulity and the question "Why?" Another similar group of individuals were asked whether they would take part in an experiment of brief duration. When they agreed to do so, they too were asked to perform five push-ups. Their typical response was 'Where?'"
Also hidden in the fine print: Players were told they would receive money for two randomly chosen games out of ten. This gives the game more of a gambling twist and does not serve to clarify the nature of the game.
It could be argued that there’s a fine line between explaining the game and demand characteristics, but in their case it was probably just a shortage of cash (we can empathize with that).
Lastly, they argue that a player privately declining his share cannot be accounted for by inequity aversion (because it increases inequity) or reciprocity (symbolic punishment wouldn’t make sense if the punished one doesn’t get wind of it).
Instead they postulate emotion as a commitment device as an explanatory factor. Someone who has a reputation for being angered by unfair offers and declining them in defiance of rationality has an edge over someone who always acts rationally: Anticipating the anger because he knows the player’s reputation, a proposer will offer a fair deal. A rational player will be trapped as he is known to acquiesce even when offered an insultingly low share.
Although we dig that they shed light on the difference between proximate and ultimate rationality, we don’t buy it just yet. They reason that emotional reactions should happen consistently, even when the choice is private. We believe this understanding of emotional commitment intersects heavily with the concept of honour. Cultures are sometimes contrasted as “of law” versus “of honour” in the literature. They don’t make this connection, but exciting differences across cultures would be expected from this interpretation.
In their study, the possibility that demand characteristics were present dearly hurts the conclusion. Players still may have wanted to assert moral superiority to the experimenter.
Do you know studies that improve upon this research? Is honour an emotion? What about shame? Do you disagree outright? Let us know in the comments!
This entry by Ruben Arslan is part of an on-going project that aims to integrates Science Blogging into our teaching at Humboldt-University's Institute for Theoretical Biology. Find out more here.
Bolton, G.E., & Zwick, R. (1995). Anonymity versus Punishment in Ultimatum Bargaining Games and Economic Behavior, 10 (1), 95-121 DOI: 10.1006/game.1995.1026
Orne, M.T. (1962). On the social psychology of the psychological experiment: With particular reference to demand characteristics and their implications. American Psychologist, 17 (11), 776-783 DOI: 10.1037/h0043424
Yamagishi T, Horita Y, Takagishi H, Shinada M, Tanida S, & Cook KS (2009). The private rejection of unfair offers and emotional commitment. Proceedings of the National Academy of Sciences of the United States of America, 106 (28), 11520-3 PMID: 19564602