Three effects of apparently superficial changes in presentation (“framing effects†in a broad sense), were replicated together in the same repeated linear public goods experiment with real financial incentives. First, 32 repetitions were presented as four phases of 8 repetitions with a break and results summary in between. Contribution levels decayed during each phase but then persistently returned to about 50% after each re-start. Second, subjects contributed more when the payoff function was decomposed in terms of a gift which is multiplied and distributed to the other players, rather than the equivalent public good from which everyone benefits. Third, subjects contributed more following a comprehension task which asks them to calculate the benefits to the group of various actions (the “We†frame), rather than the benefits to themselves (the “I†frame). These results suggest that aspects of presentation may have strong and replicable effects on experimental findings, even when care is taken to make the language and presentation of instructions as neutral as possible. Experimental economists should therefore give careful consideration to potential framing effects—or, better still, explicitly test for them—before making claims about the external validity of results. Copyright Kluwer Academic Publishers 2000
