Precursors of children’s false memory

False memory implantation studies have shown that it is relatively easy to induce implanted false memories in children. However, during the advent of these studies, one lingering unanswered issue concerned the precise precursors that determine the production of implanted false memories. Specifically, one unsolved issue was whether implanted false memories could also take place for implausible and negative events of which children had limited knowledge. Interest in this issue was heightened by well-known legal proceedings, such as the Oude Pekela case in which children reported having experienced bizarre and negative actions—experiences that one might assume children do not have much knowledge about (i.e., satanic abuse by clowns).

False memory models have emphasized that, in order to fuel false memory formation of fictitious events, people should first believe that the event is something plausible that could have happened to them (e.g., Pezdek, Blandon-Gitlin, Lam, Hart, & Schooler, 2006). According to this interpretation, events should first be judged to be true before details related to the event (schema-congruent information) can be retrieved. This view postulates that plausible events are frequently experiences that consist of considerable script knowledge. So when information is retrieved that is highly related to the general knowledge of such an event (i.e., script knowledge), participants are more likely to believe and come to remember that a false event had actually happened to them. Furthermore, how the emotional aspects of experiences might interact with plausibility and script knowledge was not obvious. Clearly, negative events are more likely to be recollected because of their distinctiveness and increased arousal, yet whether such events are also more likely to be distorted was at that time unclear (Porter, ten Brinke, Riley, & Baker, 2014).

Plausibility

One of the first studies that examined the effect of plausibility on the formation of implanted false memories (in adults) was conducted by Pezdek, Finger, and Hodge (1997). In two experiments, they manipulated the degree of plausibility and assessed its influence on whether participants succumbed to suggestive pressure. Specifically, in Experiment 1, Jewish and Catholic students received three true and two false descriptions of (non)experienced events. The false events described religious rituals: one specific for the Jewish community (Shabbot) and one directed at the Catholic community (Communion). The researchers found that both Jewish and Catholic students were most likely to falsely recollect the ritual that was deemed plausible for them (Shabbot or Communion, respectively). In the second experiment, adult participants heard two false stories, with one story depicting a plausible event (i.e., lost in a shopping mall) and the other an implausible occasion (i.e., receiving an enema). Like the first experiment, the plausible event gave rise to significantly more false memories relative to the implausible event. Using a similar procedure as in Experiment 2, Pezdek and Hodge (1999) extended their approach and tested 5- to 7-year-old and 9- to 12-year-old children as well. The pattern of findings was nearly identical. The authors once more showed that plausible events were more easily planted into children’s memory than implausible events.

Although these findings concerning plausibility and false memory propensity seemed to provide a coherent picture, Pezdek and colleagues assumed that plausible events are events for which people have considerable script knowledge. That is, they suggested that “in most real cases, [plausibility and schematic knowledge] are highly correlated” (p. 888; Pezdek & Hodge, 1999). Work by Scoboria, Mazzoni,

Kirsch, and Relyea (2004), however, revealed that plausibility and script knowledge were unrelated to each other. In their study, participants were asked about several events (e.g., losing a toy) and rated the plausibility, belief, and memory of those events. Some of the participants also had to provide schematic knowledge of the events. The main finding was that having a memory of an event implies that one also believes in the occurrence of the event, and this in turn implies that the event is considered to be plausible. More importantly, no relationship was found between plausibility and script knowledge.

Another important consideration is that research has shown that perceived plausibility is not fixed, but highly malleable. For example, Mazzoni, Loftus, and Kirsch (2001) examined in three experiments whether people’s judgments of the likelihood that an implausible event (i.e., witnessing demonic possession) occurred could be altered. Specifically, in one of their experiments (Experiment 1), participants were asked to indicate how likely it was that certain events could have occurred to them. Three months later, some of these participants received stories suggesting that witnessing a demonic possession was quite common in the general population, thereby manipulating the base rate information. One week after the second session, these participants were falsely told that they showed signs of having witnessed such a possession before the age of 3. Finally, one week after this meeting, participants were asked to indicate again how likely it was that they had witnessed demonic possession. Strikingly, participants increased their confidence in how likely it was such an event could have occurred to them compared to a control group who was not presented with base rate information. Thus, the experiment revealed that perceived plausibility is not fixed, but can be changed depending on manipulations such as focusing on the base rate of events occurring in the general population.

Following this line of reasoning, we examined whether such base rate manipulations could actually affect the creation of children’s false memories for an implausible event. We first conducted a pilot study to examine how certain events (e.g., UFO abduction) were rated on plausibility and valence and what people knew about them (i.e., script knowledge). Based on the results of this pilot study, we selected two events that differed in perceived plausibility but were equal in terms of valence and script knowledge.

In the subsequent implantation experiment, younger (7- to 8-year-old) and older (11- to 12-year-old) children were falsely told that they were abducted by a UFO or almost choked on a candy when they were 4 (Otgaar, Candel, Merckelbach, & Wade, 2009). Importantly, half of the children received false newspaper articles ostensibly suggesting that UFO abduction or almost choking on a candy happened quite frequently where they lived when they were 4. During two interviews, we measured the likelihood that children would form false memories. Interestingly, we found that at the second interview, children were more likely to falsely recollect that they were abducted by a flying saucer when they received the newspaper article relative to children who did not receive this manipulation. We also demonstrated that children were equally likely to produce false memories for the plausible or implausible event. The bottom-line message of these studies is that, although plausible events are extremely likely to be misremembered, even implausible events can be falsely implanted in memory. Furthermore, these experiments reveal that under certain circumstances, plausibility does not catalyze false memory propensity' and that both children and adults are equally likely to produce plausible and implausible false memories (see also Strange, Sutherland, & Garry', 2006).

 
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