How do additional alternatives affect individual choice under uncertainty?

We show, in an artefactual field economics decision-making experiment, that the addition of an alternative to a choice set can affect the measurement of farmers' risk preferences in rural Peru. We found that an alternative that would normally be considered irrelevant was chosen in Peru, and that it affected choice between other alternatives. In Montreal, the irrelevant alternative was not chosen, but also affected choices between other alternatives. Comparing choices made in Peru with those made in Montreal, we identify beliefs and cultural characteristics that are likely to lead to these results.