The Effect of Including Reflexivity Trials in Test for Equivalence Class Formation

The three defining properties of stimulus equivalence relation are reflexivity, symmetry and transitivity (Sidman & Tailby, 1982). According to Sidman (1994) all three properties must be present in order to state that an equivalence class has been established. However, tests for equivalence class formation seldom include reflexivity test trials. Therefore, the purpose of the current study was to investigate the effect of including the reflexivity, symmetry, and transitivity trials in a mixed test block. We used the linear-series training structure to form three 5-member stimulus equivalence classes. The results showed that, the likelihood of establishing the stimulus equivalence classes was low. The results from the reflexivity test trials showed that half of the participants responded in accordance to reflexivity, which, if taken for granted that these relations are given, is lower than anticipated. The results will be discussed along with providing suggestions to future studies.