Slipping Anchor? Testing the Vignettes Approach to Identification and Correction of Reporting Heterogeneity.

We propose tests of the two assumptions under which anchoring vignettes identify heterogeneity in reporting of categorical evaluations. Systematic variation in the perceived difference between any two vignette states is sufficient to reject vignette equivalence. Response consistency - the respondent uses the same response scale to evaluate the vignette and herself - is testable given sufficiently comprehensive objective indicators that independently identify response scales. Both assumptions are rejected for reporting of cognitive and physical functioning in a sample of older English individuals, although a weaker test resting on less stringent assumptions does not reject response consistency for cognition.