Smeets, P. M., & Barnes-Holmes D. (2005). Establishing equivalence classes in preschool children with many-to-one and one-to-many training protocols. Behavioural Processes, 69(3), 281-293.
The authors, researchers at the National University of Ireland and Leiden University, assessed whether the different probabilities reported in the literature of obtaining equivalence after baseline training with MTO and OTM protocols could be attributed to individual differences and, if so, whether equivalence formation could be facilitated by using familiar stimuli as nodes. The results showed that (a) the children's performances (training and testing) were not affected by the training protocol; (b) equivalence formation occurred more readily when being trained with all abstract stimuli than when familiar stimuli served as nodes; and (c) most children who passed or did not pass the equivalence test in Experiment 1 repeated their performance in Experiment 2, irrespective of the conditions that were used.