Memory suggestibility as an example of the sleeper effect

This study incorporates findings on both the sleeper effect and the suggestibility of memory and assesses the effect of source credibility and time delay on memory suggestibility. Subjects viewed a sequence of slides with four target items. A narrative followed, containing a misleading description of two target items; the other two items served as controls. The source of the narrative was attributed to either a 4-year-old boy (low-credibility source) or a memory psychologist (high-credibility source) who described the slides. A recognition memory test followed 10 min or 1 month later. The subjects in the low-credibility source condition falsely recognized significantly more misleading items in the delayed condition than in the immediate condition; in the high-credibility condition, the number of falsely recognized misleading items was high and did not differ between the delayed and the immediate conditions. This significant interaction between source credibility, time, and misled/control conditions on the rate of falsely recognizing misled items suggests that, with the passage of time, item and source information become less strongly associated in memory. The cognitive processes underlying the sleeper effect appear to be similar to those underlying memory suggestibility.