A theoretical account of the mirror effect for word frequency and of dissociations in the pattern of responding Remember vs. Know (R vs. K) for low- and high-frequency words was tested both empirically and computationally by comparing predicted with observed data theory in 3 experiments. The SAC (Source of Activation Confusion) theory of memory makes the novel prediction of more K responses for high- than for low-frequency words, for both old and new items. Two experiments used a continuous presentation and judgment paradigm that presented words up to 10 times. The computer simulation closely modeled the pattern of results, fitting new Know and Remember patterns of responding at each level of experimental presentation and for both levels of word frequency for each participant. Experiment 3 required list discrimination after each R response (Group 1) or after an R or K response (Group 2). List accuracy was better following R responses. All experiments were modeled using the same parameter values.

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The fan effect (Anderson, 1974) has been attributed to interference among competing associations to a concept. Recently, it has been suggested that such effects might be due to multiple mental models (Radvansky, Spieler, & Zacks, 1993) or suppression of concepts (Anderson & Spellman, 1995; Conway & Engle, 1994). We show that the ACT-R (Adaptive Control of Thought-Rational) theory, which embodies associative interference, is consistent with the Radvansky et al results and we fail to find any evidence for concept suppression in a new fan experiment. The ACT-R model provides good quantitative fits to the results from a variety of experiments. The three key concepts in these fits are (a) the associative strength between two concepts reflect the degree to which one concept predicts the other; (b) foils are rejected by retrieving mismatching facts; and (c) subjects can adjust the relative weights they give to various cues in retrieval.