Editing misleading information from memory: Evidence for the coexistence of original and postevent information

ROBERT E. CHRISTIAANSEN 0 KATHLEEN OCHALEK 0 0 Lawrence University , Appleton, Wisconsin When misleading postevent information biases one's memory for an event, what is the fate of the original, accurate information? One possibility is that the new information and the original information coexist in memory, but that the former is simply more accessible. A second hypothesis suggests that the new information replaces the old, and memory is irreversibly altered. Using various retrieval techniques, Loftus and her associates (Greene, Flynn, & Loftus, 1982; Loftus, 1979a, 1979b) have failed repeatedly in attempts to recover original memories after postevent biasing, a finding that supports the alteration hypothesis. In the present study, postevent biasing was demonstrated in two experiments. In each experiment, some subjects were given a warning that the postevent information had included a few inaccurate details. These subjects were able to edit out the inaccurate details and to recover the original facts when the warning came as much as 45 min after they had read the misleading information, a result that argues for the coexistence of memories. Successful recovery of the original memories was apparently due to the clarity of the warning and to an improved technique for assessing the retrieval of original memories. - information, not when they followed the reading of that information. Thus, subjects could apparently detect inaccurate statements in the narrative if they were warned, but could not edit out these inaccuracies once encoded in memory. Despite these and other failures (Loftus, 1979a) to find evidence for coexistence, we felt there were several reasons to question the rejection of this hypothesis and the acceptance of the alteration hypothesis. Our first concern was a problem clearly acknowledged by Loftus and her associates (Loftus, 1979a; Loftus & Loftus, 1980). Although attempts to recover original memories potentially can provide evidence for coexistence if the original information is successfully recovered, failure to recover original memories is only suggestive evidence in favor of alteration. One can always argue that the original memory still exists but that the appropriate retrieval method was not used. This logical difficulty alone might be justification enough for a few more attempts at demonstrating coexistence. But our concern went beyond a feeling that "one more try" was needed. Two aspects of the previously described studies might well have affected the chances of successfully demon strating coexistence of memories. First of all, an even more explicit warning than that used by Greene et aI. (1982) may be necessary to ensure that subjects are motivated to search memory for incon sistent pieces of information. Greene et aI. told subjects that some of the information in the narrative they read "may have been inaccurate" because the police cadet (who supposedly had written it) was inexperienced. With a stronger warning, memory search should be perceived as more likely to succeed in finding inconsistencies. In addition, not mentioning a cause for the errors should eliminate the possibility that subjects dismiss the "warn ing" as unimportant to their task and think of it as a mere notation of some accidents for which the experi menter is offering an explanation. One purpose, then, of the present study was to attempt to recover coexist ing memories by using an unambiguous warning that asserted that errors did exist in the narrative. In addition to the clarity of the warning, the present study included an assessment of whether the original event information was actually encoded in memory. Proof that the original information was indeed encoded would seem to be desirable for any test designed to determine if subjects can recover such memories; yet, in all but one of the studies testing the various recovery techniques, no initial accuracy test was given before the biasing information was introduced.' Without such a test, one cannot identify which specific information was encoded by each subject, and therefore what is po tentially recoverable. Performance by control groups can, of course, indicate the general level of accuracy when no postevent information is introduced, but reli ance on such estimates may introduce an artifact that reduces the apparent effect of the recovery technique. When the tests include items that a given subject may never have encoded, as must surely happen in these studies, this can only mitigate the success of the various recovery techniques. In the present study, an initial accuracy test assessed memory for the specific facts that were later biased, and only those items for which a sub ject was initially accurate were included in our principal analyses. Therefore, only those memories that were potentially recoverable were examined, thus providing a fair test for the effectiveness of the warnings. In Experiment 1, there were four conditions. The subjects in the neutral condition served as a control group and did not receive misleading information, whereas the subjects in the biased condition did receive misleading postevent information. The subjects in the biased-immediately-informed and biased-delayed informed conditions also received misleading postevent information. In the former condition, the subjects were warned, immediately after having read the narrative, that they had read some inaccurate information, and in the latter condition, they received this same warning approximately 45 min later, just prior to the final test. Subjects Sixty-eight students from Lawrence University and one individual from the city of Appleton participated in the study. The data from only 61 subjects were used because 8 of the students indicated, on debriefing questions, that they knew something about the purpose of the experiment from the outset. This high number was probably due to the fact that the experi ment was done on a small campus on which previous memory biasing research had been conducted. Materials Slides. The event to be remembered was a series of 24 color slides depicting an ambiguous shoplifting event in a department store. The slide sequence opens with a young man walking down the aisle of the store. After purchasing a small item, the young man walks through the sporting goods department and looks at a compass. As the manager of the store watches, the young man turns and appears to reach into his pocket. Later, the young man walks toward an exit with the item he previously has paid for, but the manager is standing in the doorway. Upon seeing the manager, the young man walks to the back of the store and into a room full of stereo equipment, with the manager following him. A struggle ensues in which the manager grabs the young man, but the young man gets away and runs out of the store. Accuracy tests. The initial accuracy test consisted of 31 items that addressed diverse details of the event. With the excep tion of two open- (...truncated)