An examination of the proportional difference model to describe and predict health decisions

Three studies tested whether the proportional difference rule, PD, of the Stochastic Difference Model (SDM, González-Vallejo, 2002) describes decisions under both risk and certainty with a single rule. The SDM characterizes how individuals make trade-offs between non-comparable attributes when choosing. The PD rule assumes that options are compared attribute-wise: proportional advantages favoring an option in a given attribute move the decision maker towards that option; proportional disadvantages move the decision maker away from that option. The model was tested in health domains: choices of health treatments and of health products. Health treatment options were described in terms of probability of survival and probability of side effects resulting from the treatment. More invasive treatments offered higher survival rates, but were also more likely to result in side effects. Health products were cereals and energy drinks. Data across the different health domains showed good support for PD using different model evaluation methods.

► The proportional difference (PD) model of the SDM theory was tested in health domains.
► The domains deal with decisions under risk and certainty.
► PD was compared to logically derived alternative utility models and to the Priority Heuristics.
► PD’s single trade-off process performed well in multiple model tests.