Visual analog scales, standard gambles, and relative risk aversion

Background. It has been argued that visual analog scales (VASs) elicit an individual's measurable value function. The theoretical link between an individual's measurable value function v(.) and his or her von Neumann-Morgenstern utility function u(.) appears to provide a justification for transforming VAS scores into standard gamble (SG) utilities. However, VAS scores have been found to be subject to the effects of context, which casts doubt that the procedure is properly revealing v(.). Methods. The authors tested for the effects of context on VAS and SG scores. They also explored whether the range-frequency (R-F) model of Parducci offers a means of correcting VAS scores for the effects of context. Results and conclusions. The R-F model may provide a means of correcting VAS scores for the effects of context, but no stable relationship exists between these corrected scores and SG utilities. Hence, there remain no grounds for transforming VAS scores into SG utilities. Key words: visual analog scales; standard gambles; measurable value functions; context effects; range-frequency theory.