Overview

Reason for this study: Many studies have investigated source monitoring errors and misinformation effects, but the author feels that the results can be easily misinterpreted. In the present study, he attempts to better explain the phenomenon of misinformation effects, using slightly different methods than previous researchers.

Problems with interpreting misinformation effects:

Demand Characteristics: *People may believe the postevent information accurately represents the original event. McCloskey and Zaragoza (1985) eliminated the suggested item as a memory option to control for DC.
*People may choose the suggested event b/c they assume if the experimenter prepared the information, then it should be correct. Adding a warning before the test provides a good control for this effect.

Source Guessing: People may choose one of the options that indicate an event occurred, b/c they ‘know’ it happened somewhere, but don’t really know where. Control: Adding a ‘know’ option to eliminate source guessing.

The present study

Experiment 1:

• 56 subjects watched a video of an armed robbery in a convenience store. They were told that their memory would be tested for peripheral details of the crime scene.
• Long Delay Condition: One hr. after the crime, half of the subjects answered misleading questions. Then, 48 hours later they did a filler task, followed by the source monitoring test 1 hr. after that.
• Short Delay Condition: One hr. after the crime, half of the subjects did a filler task. Then, 48 hours later they answered the misleading questions, followed by the SM test 1 hr. after that.
• Misleading questions were counterbalanced with half mentioning a critical item not in the video and half mentioning a non-critical object in the video or a critical item in neutral form. These questions appeared in 2 versions.
• Filler tasks were either a questionnaire a/b social desirability or an orientation task which manipulated the level of processing of non-critical items.
• A warning was given (although very slight) that some objects didn’t occur in the video or questions.
• Subjects indicated ‘V’ for Video, ‘Q’ for Questions, ‘both’, ‘N’ for No memory, or ‘K’ for Know. Following ‘K’, subjects guessed a possible source.
• There were 16 objects on the recognition test. (10 critical and 6 filler)

Short delay: 48 hrs. b/w video and questions & 1 hr. b/w questions and test (p. 276)

Long delay: 1 hr. b/w video and questions & 48 hrs. b/w questions and test.

Results:

• Overall, subjects indicated that objects suggested in the misleading questions were more likely to have been seen in the video than were control objects.
• Suggested objects were more likely to be contributed to ‘both’ (instead of ‘video only’) than were control objects.
• There was an item by suggestion interaction and delay by suggestion interaction, indicating that as delay increased, so did the size of the misinformation effect for ‘video only’ responses.
• The ‘know’ responses were non-significant

(It appears that the misinformation effect in this expt. was due to false conscious recollection of the suggested objects. Even if people have an accurate memory of the source, they can still come to believe that they encountered an item from a different source.)

• If an object was presented in the questions, subjects were more likely to remember the source than if the object was presented in the video.

(Poor memory for the video probably contributed to the misinformation effect.)

Because the delay conditions were confounded, a new experiment was employed.

Discrepancy detection (DD): The ability to detect a discrepancy b/w the event information and the post-event misinformation. If DD is high, then misinformation effect (ME) would be small and vice-versa. So, if the interval b/w video and question is longer, DD would be less likely to occur yielding a greater ME. In Expt. 1, if the V-Q delay was longer, then the Q-T delay was shorter. So, we really don’t know which delay did what! Expt. 2 was necessary to determine if the effect of ‘video only’ responses was a result of the change to the V-Q delay or the Q-T delay. (See Table 2, p. 276)

• 46 subjects watched the video and answered misleading questions 30 min. later.
• The test was administered one hour after completion of the questions.
• All the materials were the same as in Expt. 1.

• Overall, subjects seemed to rate the suggested items as having been seen more often than rating the control items as having been seen.
• There was no significant effect for ‘know’ responses, so this supports expt. 1 in that subjects are displaying misinformation effects due to false recollections.
• The difference b/w the effect of suggestion on ‘video only’ responses in Expt. 2 and Expt. 1/short delay was non-significant. Therefore, increasing the delay from question to test caused the effect of suggestion, not the decreased delay from video to question.
• As in Expt. 1, subjects had better memory for items presented in the questions than in the video.

General Discussion

• People most likely made source errors caused by false recollection of seeing objects that were only read about in the questions.

This study helps to eliminate possible misinterpretations of the misinformation effect, confirming the occurrence of false recollection, rather than source guessing.

• Higham makes a comparison with sleeper/false fame experiments in which subjects chose mutually exclusive sources. However, in the present study, many chose ‘both video and questions.’

Higham discusses opposition instructions, which can cause subjects to choose a category indicating that an item was never encountered. He states that this can cause an "underestimation of the proportion of misled participants who come to believe that they saw a suggested detail" (p. 282).

• False recollection of a detail in an event still occurs despite subjects’ knowledge that it could have been encountered in post-event information.