On the difference between strength-based and frequency-based mirror effects in recognition memory

A mirror effect can be produced by manipulating word class (e.g., high vs. low frequency) or by manipulating strength (e.g., short vs. long study time). The results of 5 experiments reported here suggest that a strength-based mirror effect is caused by a shift in the location of the decision criterion, whereas a frequency-based mirror effect occurs although the criterion remains fixed with respect to word frequency. Evidence supporting these claims is provided by a series of studies in which high frequency (HF) words were differentially strengthened (and sometimes differentially colored) during list presentation. That manipulation increased the HF hit rate above that for low frequency (LF) words without selectively decreasing the HF false alarm rate, just as a fixed-criterion account of the word-frequency mirror effect predicts.