Intralist and Extralist Sources of Distinctiveness and the Bizarreness Effect: The Importance of Contrast

Abstract

The roles played by intralist and extralist distinctiveness with respect to the recall of bizarre and common sentences was investigated in two experiments. In Experiment 1, a greater percentage of bizarre than common sentences was accessed in predominantly common lists and in lists containing equal numbers of common and bizarre items. Reciprocally, a greater percentage of common than bizarre sentences was accessed in predominantly bizarre lists. In Experiment 2, contrast (i.e., the degree of separation between common and bizarre sentence types) was manipulated. In high-contrast lists, intralist distinctiveness was more powerful than extralist distinctiveness associated with bizarreness. The opposite was true for low-contrast lists. The results support an extension of the distinctiveness hypothesis to include the independent effects of intralist and extralist distinctiveness and suggest related limiting conditions. In recent years, much of the research investigating bizarre mnemonics has been guided by explanations and hypotheses that incorporate the distinctiveness construct. McDaniel and Einstein (1986), who provided the first formal extension of the distinctiveness account to bizarreness research, have suggested that distinctiveness may be at the heart of the bizarreness effect. In their review of the previous literature, McDaniel and Einstein found that investigators that have found bizarreness to be an effective memory aid have usually incorporated the use of a withinlist design. Those that have used a between-list design tended not to find the significant effect. Thus, when subjects are presented with bizarre and common items within the same list, results indicate a mnemonic advantage for the bizarre items. In their study, McDaniel and Einstein hypothesized that, in a mixed list, the bizarre items are made distinct by the presence of the common items and are, therefore, better recalled. To support their distinctiveness hypothesis, they demonstrated a mnemonic benefit for bizarre sentences accessed when subjects were presented with lists containing equal numbers of common and bizarre sentences. Also in support of the distinctiveness hypothesis, Einstein, McDaniel, and Lackey (1989) showed that when subjects were presented with unmixed