This study incorporates findings on both the sleeper effect and the su
ggestibility of memory and assesses the effect of source credibility a
nd time delay on memory suggestibility. Subjects viewed a sequence of
slides with four target items. A narrative followed, containing a misl
eading description of two target items; the other two items served as
controls. The source of the narrative was attributed to either a 4-yea
r-old boy (low-credibility source) or a memory psychologist (high-cred
ibility source) who described the slides. A recognition memory test fo
llowed 10 min or 1 month later. The subjects in the low-credibility so
urce 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 ite
ms was high and did not differ between the delayed and the immediate c
onditions. This significant interaction between source credibility, ti
me, and misled/control conditions on the rate of falsely recognizing m
isled items suggests that, with the passage of time, item and source i
nformation become less strongly associated in memory. The cognitive pr
ocesses underlying the sleeper effect appear to be similar to those un
derlying memory suggestibility.