Sunk Cost and Commitment to Medical Treatment

The influence of prior, irretrievable, investment (sunk cost) on commitment to medical treatment was investigated. Three studies were run investigating the influence of sunk cost in the form of money, time, and effort. A total of 637 participants (314 male) with a mean age of 19.58 years were recruited from an undergraduate population. A computer program simulated the process of arranging a course of physiotherapy. Participants invested one of three amounts of sunk cost (under budget, on budget, or over budget) into arranging sessions with a chiropractor. Participants then decided how much time they wished to commit to these chiropractor sessions or to an alternative treatment with a better chance of success. Results revealed a significant effect of invested money, a significant effect of invested effort, but no effect of invested time. Invested money produced a sunk cost effect, while invested effort appeared to exert influence via cognitive dissonance. The implications for healthcare decision-making are discussed.