Cullinan, V., Barnes-Holmes, D., & Smeets, P. M. (2000). A precursor to the relational evaluation procedure: Analyzing stimulus equivalence II. The Psychological Record, 50, 467-492.
The authors, researchers at the National University of Cork and University of Leiden, conducted a series of experiments examined the precursor to the relational evaluation procedure (pREP). The pREP is capable of facilitating derived relational responding, but it is less effective than matching-to-sample (MTS) in producing equivalence class formation. All subjects reliably produced both symmetry and equivalence responding on the pREP with both familiar and novel stimuli. One of the experiments determined whether using the same stimulus sets across the two procedures was necessary. Results showed that if symmetry and equivalence were shown on a MTS procedure followed immediately by pREP training and testing using novel stimuli, only 2 out of 4 subjects successfully demonstrated both symmetry and equivalence using the latter procedure.