Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy



Major Professor

E. Ohmer Milton

Committee Members

Orin B. Graff, J.M. Porter, Jr., J.T. Drake, W.O. Jenkins


Introduction: Abbreviated

The laws governing acquisition and maintenance of behavior have occupied learning theorists in psychology for many years with the result that a great deal of data are available which demonstrate various factors influencing the acquisition of both simple and complex habits. Among the hundreds of factors now known to influence learning, similarity between original and interpolated material has received much attention in retroactive and proactive inhibition settings. The interference effects of these processes with varying degrees of similarity were first stated in 1920 by Woodworth and Poffenberger (23) and separately by Foucault (23) in 1928.

From the many studies, some of which are cited below, relating to the facilitating or inhibiting effects on learning of varying degrees of similarity between original and interpolated materials, it has been shown that there are many dimensions along which the continuum of similarity can vary. Several hypotheses concerning the relationships of these factors have been stated. Among these hypotheses is found the Skaggs-Robinson hypothesis (36, 23) which states that: "As similarity between interpolation and original memorization is reduced from near identity, retention falls away to a minimum and then rises again, but with decreasing similarity it never reaches the level obtaining with maximum similarity."

This hypothesis, while an interesting and important one to learning theory, has not been demonstrated in a single experiment, although parts of it have been suggested by several studies. The purpose of the present study is to demonstrate the Skaggs-Robinson hypothesis in a retroactive inhibition setting within the theoretical framework of Guthrie's theory of learning.

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