More equal than others: Equity norms as an integration of cognitive heuristics and contextual cues in bargaining games.

Behavior in one-shot bargaining games, like the Ultimatum Game (UG), has been interpreted as an expression of social preferences, such as inequity aversion and negative reciprocity; however, the traditional UG design limits the range of possible psychological interpretation of the results. Here, we employed three different designs for ultimatum games, finding support for a more comprehensive theory: behavior is driven by cognitive factors implementing rules such as equal splitting, speaking up for the idea that equity works as a cognitive heuristic, applicable when the environment provides no reason to behave otherwise. Instead subjects deviate from this rule when environment changes, as, for instance, when personal interest is at stake. Results show that behavior varies systematically with contextual cues, balancing the self-interest with the automatic application of the equity heuristic. Thus, the context suggests the rule to be applied in a specific situation.