ABSTRACT.Aproblem central to sensory difference testing is response bias. There are two experimental strategies for dealing with this problem. The first is to use forced choice procedures, like the common duo‐trio or triangle tests, while the second is to use signal detection measures like d′, P(A) and the R‐index. These strategies are explained and discussed. The relationship between the R‐index and the other signal detection measures is explained. The relationship between R‐index values obtained by rating and ranking is explored, as are the alternative computations of the R‐index by ranking: