The research puts more evidence behind the adage that first impressions are the most lasting. Ecker conducted two experiments using a story about a warehouse fire, with "misinformation" being a statement that volatile chemicals were stored in the warehouse, and the "retraction" being a statement that the warehouse was empty.
The first experiment (n=161 undergraduate students) gauged the effect of varying the strength of the misinformation or the retraction by varying the repetitions (1, 3, or none) of each. Not surprisingly, there was a positive relationship between the number of repetitions and the answers on questionnaires about the warehouse fire story. But the experiment demonstrated that even when there was only 1 occurrence of misinformation, the 3 repetitions of the retraction did not reduce the influence of the misinformation back to zero.
In the second experiment (n=138 undergraduate students) Ecker et al simulated the effect of distractions on the continued influence of misinformation. "It is well established that cognitive load—- that is, the division of attention between two tasks—can have debilitating effects on memory retrieval," they write. "Cognitive load at misinformation encoding should therefore reduce the continued influence of misinformation." Indeed, the experimental results bear out this hypothesis, but again influence of the misinformation was never reduced to zero.
Ironically, a reference in the paper's introduction may have coded some "misinformation" about the authors' professional motives in my mind. They write,
To use a notorious real-world example, the Bush administration purportedly made 935 false statements about the security risk posed by Iraq in the 2 years following 9/11 (Lewis & Reading-Smith, 2008). It is possible that the reiteration of this misinformation (i.e., that Iraq possessed WMDs) led to particularly powerful continued influence (e.g., the widespread continued belief in the existence of WMDs in Iraq; Kull et al., 2003; Lewandowsky et al., 2005, 2009).Although the paper does seem well-written and well-reported, that statement carried enough political-zealot baggage to make look more closely than usual for possible flaws in the rest of the paper. And, even though I am cognizant of that bias, there is no easy way to erase it from my mind.
Ecker, U. K. H., Lewandowsky, S., Swire, B., & Chang, D. 2011. Correcting false information in memory: Manipulating the strength of misinformation encoding and its retraction. Psychon Bull Rev. 18:570–578.