Understanding VAS valuations: qualitative data on the cognitive process.

Eliciting people's value is a central pursuit in health economics. We explored approaches to valuing a health state on a visual analog scale (VAS). Additionally, we examined whether dual processing (an interaction between automatic and controlled information processing) occurred during VAS valuation. In the first experiment, respondents were probed for their approach after valuation on a VAS. After inductive generalization, we grouped the approaches: (1) 'Sort-of ' (automatic processing), (2) 'Bisection of line first', (3) 'Numerical expression', and (4) 'Dividing into smaller segments'. In the second experiment, a short questionnaire followed the VAS in which these approaches were systematically assessed, as was awareness of the approach used, intention to re-use the approach the next time (confidence), and basis of the approach. Data showed that the 'Sort-of' approach was used most often, followed by the 'Bisection-first' approach. We argue that dual processing occurs during performance on the VAS. Awareness of the approach used was lower when an intuitive approach was used. A reasoned approach had a higher correlation with confidence. Thus, awareness of approach may improve reliability. Reducing the number of health states to be valued concurrently diminishes the complexity of the task; this may enhance the validity of the VAS.