This standard describes the "A" — "NOT A" test for use in sensory analysis as a) a differentiation test, especially for the evaluation of samples that present variations in appearance (it is difficult to obtain samples completely identical repeats) or in the aftertaste (it is difficult to estimate directly); b) recognition test, especially to determine whether a taster or group of tasters identifies a new stimulus with respect to a known one (for example, recognition of the sweet flavor quality of a new sweetener); c) perception test, to determine the sensitivity of a subject to a particular stimulus. Some examples of its practical application are given in Annex A.