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. In recent years, a well-known empirical regularity known as the mirror effect has commanded a great deal of attention. The mirror effect refers to the relationship between hit and false alarm rates in two conditions associated with different levels of recognition accuracy. Specifically, a minor effect is said to exist when the condition associated with more accurate recognition performance is characterized by both a higher hit rate and a lower false alarm rate than the less accurate condition. This effect is so reliably observed that Glanzer, Adams, Iverson, and Kim (1993) described it as a "regularity of recognition memory.*' The mirror effect can be produced by manipulating either the class or the strength of the items presented for study. The most common class manipulation is based on word fre-quency (high vs. low), whereas strength is usually manipu-lated by varying study time or number of item presentations. The consistency of the mirror effect across different methods of manipulating recognition accuracy suggests the influence of a single underlying mechanism. In terms of signal detection theory, that mechanism is often thought to be a shift in the criterion for deciding whether to respond "yes" or "no " to a test item