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(1974). Isolation Effect in Immediate and Delayed Free Recall. The Journal of General Psychology: Vol. 91, No. 1, pp. 81-85.

Sixty college students learned by the study-recall method a serial list of 11 CVCs with the central item isolated in different degrees of perceptual enhancement: shape (Eb), shape and color (Ea), or shape, color, and size (E1); the middle three items isolated (E3); the middle five items isolated (E5); or none isolated (C) to a criterion of two consecutive errorless trials. Compared to the corresponding control items, significant facilitation of isolated item (I) occurred in all experimental conditions: The magnitude of facilitation of the I (sixth item) increased as (1) the degree of perceptual enhancement increased and (2) the number of surrounding Is decreased. The item immediately following I(s) was also significantly facilitated. The findings were accounted for in terms of Gibson’s concepts of generalization and differentiation in verbal learning.

A 2 by 2 factorial design, using 40 rats in a runway, was employed to investigate the effect of initial reward on the rate of reacquisition following an interpolated nonreward training. The reacquisition rates were found to be significantly faster for the groups when the reward was the same in the initial and reacquisition phases (transfer shift) than when it was different (nontransfer shift). In the nontransfer shift condition, there was a tendency for the group with a gain in stimulus intensity (V) to adjust the reacquisition asymptotic level faster than did the group with a loss in V.