1. Campione, J., Hyman, L., & Zeaman, D. Dimensional shifts and reversals in retardate discrimination. In Learning and transfer in mental defectives. Progress Rep., No. 4, 1963, 134–142.
2. Eimas, P. D. Effects of overlearning, transfer, and age on the discrimination learning of children. Unpublished study, 1965.
3. Kendler, H. H., & Kendler, T. S. Vertical and horizontal processes in problem solving. Psychol. Rev., 1962, 69, 1–16.
4. Shepp, B. E., & Eimas, P. D. Intradimensional and extradimension-al shifts in the rat. J. comp. physiol. Psychol., 1964, 57, 357–361.
5. Tighe, L. S., & Tighe, T. J. Overtraining and discrimination shift behavior in children. Psychon. Sci., 1965, 2, 365–366.