Categorical Judgment with a Variable Decision Rule
  A new Thurstonian rating scale model uses a variable decision rule (VDR) that incorporates three previously formulated, distinct decision rules. The model includes probabilities for choosing each rule, along with Gaussian representation and criterion densities. Numerical optimisation techniques were validated through demonstrating that the model fits simulated data tightly. For simulations with 400 trials per stimulus (tps), useful information emerged about the generating parameters. However, larger experiments (e.g. 4000 tps) proved desirable for better recovery of generating parameters and to support trustworthy choices between competing models by the Akaike Information Criterion. In reanalyses of experiments by others, the VDR model explained most of the data better than did classical signal detection theory models. 
Burton Rosner and Greg Kochanski
stat.ME