Take a 2AFC task, where people also give a measure of confidence. In the framework of signal detection theory, the criterion values for each confidence level are simply additional criteria, placed on the same internal response axis as the (first order task) decision criterion.
Can I estimate the values of these additional confidence criteria from the data of a subject? If so, how? Would I simply take all trials with (say) confidence = 3, and calculate the criterion based on those trials alone?