Barnes, D., Browne, M., Smeets, P., & Roche, B. (1995). A transfer of functions and a conditional transfer of functions through equivalence relations in three to six year old children. The Psychological Record, 45, 405-430.
The authors, researchers at the National University of Ireland and University of Cork, conducted research on equivalence relations in which all subjects showed the predicted transfer of discriminative function through the equivalence of a stimuli.