stimulus equivalence
the condition in which two or more related stimuli elicit the same response. Stimuli meet the mathematical definition of equivalence if they can be shown to exhibit reflexivity, symmetry, and transitivity. For example, in the context of an arbitrary matching to sample procedure, if a stimulus is chosen when it also appears as the sample, reflexivity has been shown. If Stimulus A is chosen when B is the sample, and B is chosen when A is the sample, symmetry has been shown. If B is chosen when A is the sample, C is chosen when B is the sample, and C is chosen when A is the sample, transitivity has been shown.