Stimulus equivalence refers to the emergence of accurate responding between untrained stimulusstimulus relations following training of other relations It involves three key properties reflexivity symmetry and transitivity Reflexivity AA is the ability to match a stimulus to itself eg matching a picture of a dog to an identical picture of a dog Symmetry If AB then BA is the ability to reverse the direction of a trained matching relation eg if taught to select a picture of a dog when given the spoken word dog the learner can then select the spoken word dog when shown the picture of a dog without direct training Transitivity If AB and BC then AC is the most complex and represents the ultimate goal It describes the emergence of a new untrained stimulusstimulus relation as a result of training two other stimulusstimulus relations that share a common member In the example provided if A picture of dog B spoken word dog and B spoken word dog C written word DOG then the ultimate goal is for the learner to demonstrate that A picture of dog C written word DOG and generalize this to the actual animal without specific training for that AC relationship This property is crucial for generalization concept formation and the development of complex language and cognitive skills Reactivity on the other hand is an entirely different concept referring to a change in behavior due to being observed and is unrelated to stimulus equivalence