Observed discriminability is more variable than predicted by signal detection theory

Food scientists and technologists are interested in how sensitive judges and consumers are to changes in product formulations. Numerous approaches to measuring sensitivity have developed at a rapid rate in the last 25 years, however, the evaluation and assessment of sensory tasks is still ongoing. The current study compared the efficiency of four difference tests (A-Not A, A-Not AR, 2-AFC, 2-AFCR) across three concentrations (difficulty levels) of orange essence. To determine which of the four tasks had the lowest variance in d′, the decision strategy used by the judges first had to be ascertained. Using the rating-scale approach of signal detection theory, four estimates of sensitivity, d′, were obtained for each judge (n = 10) at each of the three difficulty levels, for all four tasks. Results indicate that the majority of judges adopted the β-strategy for the A-Not A and A-Not AR tasks, and the β/τ-strategy for the 2-AFC and 2-AFCR tasks. The A-Not A and A-Not AR tasks produced greater estimates of d′ than the other two tasks, and the A-Not A task exhibited a greater variance in d′ than the other three tasks.