Single and multidimensional same-different judgments

A probabilistic, multidimensional Thurstonian model for treating same-different judgments was tested in an experiment in which subjects made single-dimensional and two-dimensional same-different judgments. Strong asymmetries in the data required adding temporal bias parameters to the model. The model, with bias parameters, accounted for the single- and two-dimensional judgments reasonably well, but the parameters were not invariant between the different solutions. The two-dimensional judgments were more variable than expected on the basis of the single-dimensional judgments.