It has been suggested that individuals employ simple decision heuristics when answering stated preference questions. Evidence from discrete choice experiments of individuals failing to trade may indicate that they employ simple decision making heuristics. However, individuals might not trade because their preferences are not captured by the range of trade-offs they are offered. This is explored by offering a series of choices where the trade-offs implied by subsequent choices depend on the subject's responses to previous choices. The results suggest that individuals answer discrete choices without recourse to simplifying heuristics, and that information is generated on their preferences rather than on how they make such choices.