Evidence against associative blocking as a cause of cue-independent retrieval-induced forgetting

Selectively retrieving an item from long-term memory reduces the accessibility of competing traces, a phenomenon known as retrieval-induced forgetting (RIF). RIF exhibits cue independence, or the tendency for forgetting to generalize to novel test cues, suggesting an inhibitory basis for this phenomenon. An alternative view (Camp, Pecher, & Schmidt, 2007; Camp et al., 2009; Perfect et al., 2004) suggests that using novel test cues to measure cue independence actually engenders associative interference when participants covertly supplement retrieval with practiced cues that then associatively block retrieval. Accordingly, the covert-cueing hypothesis assumes that the relative strength of the practiced items at final test – and not the inhibition levied on the unpracticed items during retrieval practice – underlies cue-independent forgetting. As such, this perspective predicts that strengthening practiced items by any means, even if not via retrieval practice, should induce forgetting. Contrary to these predictions, however, we present clear evidence that cue-independent forgetting is induced by retrieval practice and not by repeated study exposures. This dissociation occurred despite significant, comparable levels of strengthening of practiced items in each case, and despite the use of Anderson and Spellman's original (1995) independent probe method criticized by covert-cueing theorists as being especially conducive to associative blocking. These results demonstrate that cue-independent RIF is unrelated to the strengthening of practiced items, and thereby fail to support a key prediction of the covert-cueing hypothesis. The results, instead, favor a role of inhibition in resolving retrieval interference.