For each model for two-feature objects, we calculated the response probabilities as follows. Each two-feature trial is characterized by change magnitude vectors of orientation and color, denoted by Δori and Δcol, respectively, which depend on the condition (e.g., in Condition C, one of the vectors is the zero vector, whereas in Condition D, neither is). In each experimental condition, we estimated the model observer's probability of a correct response, p(correct|Δori, Δcol, ω), through Monte Carlo simulations with 1,280 samples of κori,x, κori,y, xori, yori, κcol,x, κcol,y, xcol, and yori.