Three groups of preschool children received relevant verbal pretraining followed by a simultaneous discrimination learning task in which two irrelevant dimensions varied within settings. In Group B, the irrelevant dimensions varied between settings in pretraining, whereas in both Group W and Group WO, the irrelevant dimensions varied within settings during pretraining. The latter groups differed only in that Group WO was required to name the relevant dimensional values overtly during discrimination learning. Discrimination performance in Group W was significantly superior to that in Group B and did not differ from that in Group WO. The results are consistent with either or both of the following assumptions: (1) Irrelevant dimensional responses were extinguished during pretraining in Group W; (2) stimulus novelty increased the occurrence of irrelevant dimensional responses during discrimination learning in Group B. © 1975, The Psychonomic Society, Inc.. All rights reserved.