“…Previous studies have shown that, after a history of responding to a particular set of tasks (e.g., simple discriminations) or (unitary) stimuli, mentally young populations frequently do not adapt their performances when more complex tasks (e.g., conditional discriminations) or stimuli (compounds) are introduced (Singh & Solman, 1990;Smeets, Barnes, Schenk, & Darcheville, 1996;Stromer, Mcllvane, Dube, & Mackay, 1993). Specifically, the current research examined whether, following conditional discrimination training with unitary stimuli (A-B and P-O), procedures that had been successfully used for training the AB-X relations and testing transfer (PO-X) in older children and adults in previous research (Carpentier, Smeets, & Barnes-Holmes, 2000;Perez-Gonzalez, 1994, Perez-Gonzalez & Serna, 1993 would be appropriate for preschoolers.…”