Effect of forget instructions with and without the conditions for selective search*.

A PA probe experiment was conducted to determine whether a mechanism other than selective search is involved in the Only effect of directed forgetting. To accomplish this, a small number of trials which tested all pairs in the list successively ("all" trials) were intermixed with the standard single-probe trials. On "single" trials, both pretest mechanisms and selective search may operate, but on "all" trials, selective search was eliminated. The analysis compared the Only effect and intrusion data under these two conditions and examined the fate of to-be-forgotten (TBF) recall on "all" trials. The evidence confirmed the major role of selective search in producing the Only effect. It was concluded that if a pretest mechanism was operative, it did not have the properties of a voluntary forgetting mechanism and it had only a small effect on the first half of the list.