Sensitivity index d'

dprime calculates the sensitivity index d' and bias criterion c from signal detection theory

The sensitivity index d' measures the distance between the signal and the noise means in standard deviation units. c is the distance of the bias criterion from the point where neither response is favored, also

in standard units. Positive c values indicate a bias towards high hit rates and false alarm rates. Correction of perfect rates according to 1/2N rule is included.

cf. Stanislaw H, Todorov N, Behav Res Meth (1999) 31, 137-149