Interference produces different forgetting rates for implicit and explicit knowledge.

Exposure to a repeating set of target strings generated by an artificial grammar in a speeded matching task generates both explicit and implicit knowledge. Previous research has shown that implicit knowledge (assessed via a priming measure) is preserved after a retention interval of one week but explicit knowledge (assessed via recognition) is significantly reduced. In two experiments, we replicated and extended Tunney's findings. Experiment 1 was a partial replication of the experiment conducted by Tunney, and demonstrated that the decline in recognition shown by Tunney was not due to a repetition of test items at the pre and post times of assessment. In addition, Experiment 1 lends credibility to Tunney's assumption that recognition scores assess explicit rather than implicit knowledge. Experiment 2 extended Tunney's findings theoretically by demonstrating that interference can produce the pattern of findings demonstrated in the present Experiment 1 as well as in Tunney.