Isobias curves in some detection tasks

Signal/noise ratio was varied in three tone-detection tasks while other conditions were held constant, generating 9 8-point and 12 12-point isobias plots. These plots were compared with the theoretical isobias curves associated with seven proposed bias measures. Each of the proposed measures covaried with signal/noise ratio in at least half of the data. For two of the plots, none of the measures was invariant. It is clear that different subjects respond quite differently to change in discriminability, and the implications of this for bias measurement are discussed.