The misinformation effect happens when a person's recall of episodic memories becomes less accurate because of post-event information. For example, in a study published in 1994, subjects were initially shown one of two different series of slides that depicted a college student at the university bookstore, with different objects of the same type changed in some slides. One version of the slides would, for example, show a screwdriver while the other would show a wrench, and the audio narrative accompanying the slides would only refer to the object as a "tool". In the second phase, subjects would read a narrative description of the events in the slides, except this time a specific tool was named, which would be the incorrect tool half the time. Finally, in the third phase, subjects had to list five examples of specific types of objects, such as tools, but were told to only list examples which they had not seen in the slides. Subjects who had read an incorrect narrative were far less likely to list the written object (which they hadn't actually seen) than the control subjects (28% vs. 43%), and were far more likely to incorrectly list the item which they had actually seen (33% vs. 26%).
The misinformation effect is a prime example of retroactive interference, which occurs when information presented later interferes with the ability to retain previously encoded information. Essentially, the new information that a person receives works backward in time to distort memory of the original event. The misinformation effect has been studied since the mid-1970s. Elizabeth Loftus is one of the most influential researchers in the field. It reflects two of the cardinal sins of memory: suggestibility, the influence of others' expectations on our memory; and misattribution, information attributed to an incorrect source. Research on the misinformation effect has uncovered concerns about the permanence and reliability of memory.
Loftus, Miller, and Burns (1978) conducted the original misinformation effect study. Participants were shown a series of slides, one of which featured a car stopping in front of a stop sign. After viewing the slides, participants read a description of what they saw. Some of the participants were given descriptions that contained misinformation, which stated that the car stopped at a yield sign. Following the slides and the reading of the description, participants were tested on what they saw. The results revealed that participants who were exposed to such misinformation were more likely to report seeing a yield sign than participants who were not misinformed.
Similar methods continue to be used in misinformation effect studies. Today, standard methods involve showing subjects an event, usually in the form of a slideshow or video. The event is followed by a time delay and introduction of post-event information. Finally, participants are retested on their memory of the original event. This original study by Loftus et al. paved the way for multiple replications of the effect in order to test things like what specific processes cause the effect to occur in the first place and how individual differences influence susceptibility to the effect.
Functional magnetic resonance imaging (FMRI) from 2010 pointed to certain brain areas which were especially active when false memories were retrieved. participants studied photos during an FMRI. Later, they viewed sentences describing the photographs, some of which contained information conflicting with the photographs, i.e. misinformation. One day later, participants returned for a surprise item memory recognition test on the content of the photographs. Results showed that some participants created false memories, reporting the verbal misinformation conflicting with the photographs. During the original event phase, increased activity in left fusiform gyrus and right temporal/occipital cortex was found which may have reflected the attention to visual detail,associated with later accurate memory for the critical item(s) and thus resulted in resistance to the effects of later misinformation. Retrieval of true memories was associated with greater reactivation of sensory-specific cortices, for example, the occipital cortex for vision.
It is important to note that not everyone is equally susceptible to the misinformation effect. Individual traits and qualities can either increase or decrease one's susceptibility to recalling misinformation. Such traits and qualities include: age, working memory capacity, personality traits and imagery abilities.
Several studies have focused on the influence of the misinformation effect on various age groups. Young children are more susceptible than older children and adults to the misinformation effect. Additionally, elderly adults are more susceptible than younger adults.
Individuals with greater working memory capacity are better able to establish a more coherent image of an original event. Participants performed a dual task: simultaneously remembering a word list and judging the accuracy of arithmetic statements. Participants who were more accurate on the dual task were less susceptible to the misinformation effect. This, in turn, allowed them to reject the misinformation.
The Myers Briggs Type Indicator is one type of test used to assess participant personalities. Individuals were presented with the same misinformation procedure as that used in the original Loftus et al. study in 1978 (see above). The results were evaluated in regards to their personality type. Introvert-intuitive participants were more likely to accept both accurate and inaccurate postevent information than extrovert-sensate participants. Therefore, it was speculated that introverts are more likely to have lower confidence in their memory and are more likely to accept misinformation. Individual personality characteristics, including empathy, absorption and self-monitoring, have also been linked to greater susceptibility.
The misinformation effect has been examined in individuals with varying imagery abilities. Participants viewed a filmed event followed by descriptive statements of the events in a traditional three-stage misinformation paradigm. Participants with higher imagery abilities were more susceptible to the misinformation effect than those with lower abilities. The psychologists argued that participants with higher imagery abilities were more likely to form vivid images of the misleading information at encoding or at retrieval, therefore increasing susceptibility.
Individuals may not be actively rehearsing the details of a given event after encoding. The longer the delay between the presentation of the original event and post-event information, the more likely it is that individuals will incorporate misinformation into their final reports. Furthermore, more time to study the original event leads to lower susceptibility to the misinformation effect, due to increased rehearsal time. Elizabeth Loftus coined the term discrepancy detection principle for her observation that a person´s recollections are more likely to change, if they do not immediately detect the discrepancies between misinformation and the original event. At times people recognize a discrepancy between their memory and what they are being told. People might recollect, "I thought I saw a stop sign, but the new information mentions a yield sign, I guess I must be wrong, it was a yield sign." Although the individual recognizes the information as conflicting with their own memories they still adopt it as true. If these discrepancies are not immediately detected they are more likely to be incorporated into memory.
The more reliable the source of the post-event information, the more likely it is that participants will adopt the information into their memory. For example, Dodd and Bradshaw (1980) used slides of a car accident for their original event. They then had misinformation delivered to half of the participants by an unreliable source: a lawyer representing the driver. The remaining participants were presented with misinformation, but given no indication of the source. The misinformation was rejected by those who received information from the unreliable source and adopted by the other group of subjects.
The question of whether discussion is detrimental to memories also exists when considering what factors influence the misinformation effect. One particular study examined the effects of discussion in groups on recognition. The experimentors used three different conditions: discussion in groups with a confederate providing misinformation, discussion in groups with no confederate, and a no-discussion condition. They found that participants in the confederate condition adopted the misinformation provided by the confederate. However, there was no difference between the no-confederate and no-discussion conditions, proving that discussion (without misinformation) is neither harmful nor beneficial to memory accuracy. In an additional study, Karns et al. (2009) found that collaborative pairs showed a smaller misinformation effect than individuals. It appeared as though collaborative recall allowed witnesses to dismiss misinformation generated by an inaccurate narrative. In a 2011 study, Paterson et al. studied "memory conformity", showing students two different videos of a burglary. It was found that if witnesses who had watched the two different videos talked with one another, they would then claim to remember details shown in the video of the other witness and not their own. They continued to claim the veracity of this memory, despite warnings of misinformation.
Various inhibited states of mind such as drunkenness and hypnosis can increase misinformation effects. Assefi and Garry (2002) found that participants who believed they had consumed alcohol showed results of the misinformation effect on recall tasks. The same was true of participants under the influence of hypnosis.
Most obviously, leading questions and narrative accounts can change episodic memories and thereby affect witness' responses to questions about the original event. Additionally, witnesses are more likely to be swayed by misinformation when they are suffering from alcohol withdrawal or sleep deprivation, when interviewers are firm as opposed to friendly, and when participants experience repeated questioning about the event.
Arousal induced after learning reduces source confusion, allowing participants to better retrieve accurate details and reject misinformation. In a study of how to reduce the misinformation effect, participants viewed four short film clips, each followed by a retention test, which for some participants included misinformation. Afterward, participants viewed another film clip that was either arousing or neutral. One week later, the arousal group recognized significantly more details and endorsed significantly fewer misinformation items than the neutral group.
Educating participants about the misinformation effect can enable them to resist its influence. However, if warnings are given after the presentation of misinformation, they do not aid participants in discriminating between original and post-event information.
Research published 2008 showed that placebos enhanced memory performance. participants were given a phoney "cognitive enhancing drug" called R273. When they participated in a misinformation effect experiment, people who took R273 were more resistant to the effects of misleading postevent information. As a result of taking R273, people used stricter source monitoring and attributed their behavior to the placebo and not to themselves.
Implications of this effect on long-term memories are as follows
Some reject the notion that misinformation always causes impairment of original memories. Modified tests can be used to examine the issue of long-term memory impairment. In one example of such a test,(1985) participants were shown a burglar with a hammer. Standard post-event information claimed the weapon was a screwdriver and participants were likely to choose the screwdriver rather than the hammer as correct. In the modified test condition, postevent information was not limited to one item,instead participants had the option of the hammer and another tool (a wrench, for example). In this condition, participants generally chose the hammer, showing that there was no memory impairment.
Rich false memories are researchers' attempts to plant entire memories of events which never happened in participants' memories. Examples of such memories include fabricated stories about participants getting lost in the supermarket or shopping mall as children. Researchers often rely on suggestive interviews and the power of suggestion from family members, known as "familial informant false narrative procedure." Around 30% of subjects have gone on to produce either partial or complete false memories in these studies. There is a concern that real memories and experiences may be surfacing as a result of prodding and interviews. To deal with this concern, many researchers switched to implausible memory scenarios.
The misinformation effect can be observed in many suituations. For example, after witnessing a crime or accident there may be opportunities for witnesses to interact and share information. Late-arriving bystanders or members of the media may ask witnesses to recall the event before law enforcement or legal representatives have the opportunity to interview them. Collaborative recall may lead to a more accurate account of what happened, as opposed to individual responses that may contain more untruths after the fact.
In addition, while remembering small details may not seem important, they can matter tremendously in certain situations. A jury's perception of a defendant's guilt or innocence could depend on such a detail. If a witness remembers a moustache or a weapon when there was none, the wrong person may be wrongly convicted.