Social Cognition, Vol. 25, No. 1,2007, pp. 203-220
HINDSIGHT BIAS,
THE MISINFORMATION EFFECT,
AND FALSE AUTOBIOGRAPHICAL MEMORIES
Giuiiana Mazzoni
University of Plymouth
Maniia Vannucci
University of Firenze
Hindsight bias can be considered a type of memory distortion. In this article we compare hindsight bias to two other types of memory distortion, the
misinformation effect and the experimental creation of false autobiographical beliefs and memories. We underline the similarities in the procedures
used to elicit these phenomena and propose that the results favor a reconstructive explanation of all three. We also discuss possible mechanisms
that might subsume them.
Since the pioneering study by Fischhoff (1975) an impressive number of
studies on hindsight bias have been reported (for reviews and meta-analyses, see Christensen-Szalanski & Willham, 1991; Guilbault, Bryant,
Brockway, & Posavac, 2004; Hawkins & Hastie, 1990; Stahlberg & Maass,
1998). Many studies have investigated the effect of this phenomenon on several dimensions of cognitive and social functioning, including reasoning,
judgment, and decision making in applied settings. The settings in which
hindsight bias has been studied include jury decision making (Hastie,
Schkade, & Payne, 1999; Robbennolt & Sobus, 1997; Stallard & Worthington,
1998), medical diagnoses (Arkes, Wortmann, Saville, & Harkness, 1981),
economic expectations (Holzl, Kirchler, & Rodler, 2002), and gambling behavior (Baboushkin, Hardoon, Derevensky, & Gupta, 2001).
The authors would like to thank Markus Gschwind for helpful discussions and Irving
Kirsch for his comments on the revision of the paper.
Address correspondence to Giuiiana Mazzoni, School of Psychology, University of
Plymouth, Drake Circus, Plymouth, PL48AA, UK; E-mail to: [email protected].
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Hindsight bias, defined as a tendency to change a previous judgment in
the direction of newly provided information, has been investigated using
two main experimental designs, the hypothetical design and the memory
design (for a detailed explanation of the differences between the two designs, see Pohl, 2007-this issue). Evidence has been reported suggesting that
the effects obtained using the memory and hypothetical designs are different (Hertwig, Gigerenzer, & Hoffrage, 1997; Hoffrage, Hertwig, &
Gigerenzer, 2000). Indeed, some authors have proposed that the term "hindsight bias" be confined to the effects observed in memory-based designs,
and that the term "knew-it-all-along effect" be used to designate the effects
yielded in hypothetical designs (Hertwig et al., 1997; Stahlberg & Maass,
1998; Werth, Strack, & Forster, 2002). In the present article we focus on the
memory design as it best portrays a situation in which the provision of new
information changes the memory of the original estimate. Taken at face
value, the effect studied using this design is a memory phenomenon and
thus lends itself more easily to comparison with two other types of memory
distortions, the misinformation effect (Loftus, 1975) and the production of
false autobiographical memories (Loftus, 2004; Mazzoni & Kirsch, 2002;
Wade, Garry, Read, & Lindsay, 2002).
The similarity between hindsight bias and misinformation paradigms,
both in terms of procedure and effects, was first noted by Pohl, Schumacher,
and Friedrich (1993; see also Pohl & Gawlik, 1995). In this article, we extend
this comparison to false autobiographical memory and belief paradigms.
Although different types of memory distortions can be produced by different processes, the three paradigms examined here have in common one important feature. In each of them, new information produces systematic
memory distortions. This commonality suggests the possibility that common processes underlie these three types of phenomena. Consistent with
the idea that important similarities can be found among various memory
distortions, some authors (e.g., Brainerd & Reyna, 2002,2005) have claimed
that all memory distortions are subsumed by the same basic processes. Although we are wary of facile conceptual assimilation and overgeneralization, we believe that examining the effects of the presence of new
information in the three paradigms represents a productive way of
addressing the issue of the processes underlying them.
In the first part of this article, the three phenomena are described and the
procedural similarities and differences are reviewed. In the second part, we
review some of the theoretical accounts that have been advanced for the
three phenomena. We propose that metacognitive judgments and processes
are central to all three phenomena and represent a promising area of investigation that might help strengthen the link between hindsight bias and distortions in autobiographical memory.
HINDSIGHT BIAS AND FALSE MEMORIES
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PROCEDURAL SIMILARITIES AND DIEEERENCES
In the hindsight bias memory design, a three-stage procedure is used. Participants are first asked to estimate something (e.g., the height of the Eiffel
Tower); later they are provided with the outcome information (e.g., the actual height of the Eiffel tower) and are then asked to remember the estimate
they originally gave. The estimates given in hindsight show a bias in the direction of the correct information.
A similar three-stage procedure is also employed in the post-event misinformation paradigm (Loftus, 1975). First, participants witness an event.
Then, those in the "misled condition" are given misleading post-event misinformation that can be presented in various forms (e.g., as questions or as
descriptions of tbe witnessed event). Finally, all participants receive a
forced-choice recognition test (a memory test), in which they have to choose
between the original information and the false information (in some cases
new information is added; McCloskey & Zaragoza, 1985). Misled subjects
typically bave poorer (i.e., less-accurate) performance than control subjects
on the test question about the critical misled item (e.g., Loftus, Miller, &
Burns, 1978).
During the last few decades, research in the field of false memories has
shown that providing suggestions or additional information can do more
than just distort memory for particular aspects or details of recently witnessed events. Several paradigms have been particularly successful in creating completely false autobiographical beliefs and memories for childhood
events (see Mazzoni & Scoboria, in press, for a review). Most of these paradigms involve three stages that share common features witb the hindsight
bias memory design and the misinformation paradigm. First, tbe lack of
memory for a hypothetical autobiographical event is established. Second,
new false information is presented and suggested more or less forcefully. Finally, beliefs that the event occurred and/or memories of its occurrence are
reassessed.
One example of false autobiographical memory paradigms is the "lost in
the mall" paradigm, in which participants are told that a sibling is certain
that the false event had occurred (Loftus & Pickrell, 1995). Similarly, in the
"dream interpretation" paradigm, participants who are certain that they
had not experienced a target event have a dream interpreted as indicating
that the target event was experienced and forgotten (Mazzoni & Loftus,
1998; Mazzoni, Loftus, Seitz, & Lynn, 1999). In another paradigm, participants are informed from an apparently authoritative source tbat a particular
event (e.g., demonic possession) occurs more often than they might have
previously beheved (Mazzoni, Loftus, & Kirsch, 2001). Manipulations of
this kind produce botb false autobiographical memories (i.e., remembering
an event tbat as such had not happened) and beliefs (i.e., the false conviction
that an event had happened, whether it is remembered or not) (for a distinc-
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tion between autobiographical beliefs and memories, see Scoboria,
Mazzoni, Kirsch, & Relyea, 2004).
In summary, the paradigms used in the three areas (hindsight bias, the
misinformation effect, and false autobiographical belief and memory production) employ similar three-stage procedures and produce similar distortions in memory performance. Most importantly, in all three, the crucial
manipulation consists of providing some type of new information that
modifies a memory of earlier events.
The three paradigms are schematized in Table 1. Although substantially
similar, they are not identical. For example, the first stage of the procedure
can involve an event that has occurred (in the misinformation paradigm), an
event that has not occurred (in the false autobiographical memory paradigm), or a judgment on the part of participants that becomes the event that
is to be recalled (in the hindsight bias and autobiographical beliefs paradigm). Differences are also present in the second stage of the procedures.
While in the typical hindsight bias procedure the information is provided in
a clear, direct way and can be accurate, in the misinformation paradigm the
misleading element is inaccurate (by definition) and is never presented
alone, but is, instead, embedded within more complex information (e.g., in
the description of the original scene or in a series of questions). In false autobiographical memory paradigm information is generally inaccurate and can
be presented either directly or in a more subtle way. More crucial differences
can be found in the third stage of the procedure. Participants are asked to
provide a new estimate in the false autobiographical belief and memory paradigm, but to remember their prior, original estimate in the hindsight bias
and misinformation paradigms. In the misinformation paradigm, stage 3 is
the first instance in which they are asked to report the event previously
encoded.
These procedural differences may lead to the involvement of partially different processes in the creation of memory distortions. For example, in the
creation of false autobiographical memories, the absence of the episodic representation of the event might trigger a greater need for reconstructive processes than in hindsight bias or the misinformation effect. In this case, there
may be more freedom to rely on any information available, and hence a
greater use of inferential processes, whereas trying to remember events that
have an episodic memory representation might lead to greater emphasis on
memory-based mechanisms. Conversely, social variables might play a
larger role when the new information is stated clearly and is presented as
true.
These differences notwithstanding, the similar influence of additional information makes the comparison among the three procedures interesting
and productive. In all cases new information has a substantial impact on
memories, beliefs, and knowledge, all of which are distorted in the direction
of the information provided, no matter whether correct or misleading. In the
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TABLE 1. Similarities and Differences in Hindsight Bias, Misinformation Effect, and
Autobiographical Belief and Memory Paradigms
Paradigm
Autobiographical Belief
and Memory
Memory or belief
assessed
Stage
Hindsight Bias
Stage 1 Participant makes a
judgment
Misinformation Effect
Participant witnesses
event
Stage 2
Information provided
Accurate
Presented plainly
Information provided
Inaccurate
Embedded
Information provided
Inaccurate
Presented plainly or
embedded
Stage 3
Recall prior estimate
First recall of event
Reassess belief and/or
memory
next section, we examine potential commonalities in the processes
underlying these phenomena.
THEORETICAL EXPLANATIONS
How does new information produce the distortions observed in the hindsight bias, misinformation effect, and false autobiographical belief and
memory phenomena? Various theoretical accounts of hindsight bias and
misinformation effects have been proposed. They differ in terms of whether
the distortions are considered to be primarily due to memory impairment or
to biased reconstruction. In contrast, the production of false autobiographical memories and beliefs is generally assumed to be due to reconstructive
processes (Whittlesea & Williams, 2000; Conway, 1997). More recently, a
number of studies have examined how metacognitive judgments are crucial
in producing distortions in memory, both for hindsight bias and for autobiographical false memories and beliefs (e.g., Sanna & Schwarz, 2003; Mazzoni,
1998; Ghetti, 2003).
Memory impairment and biased reconstruction are usually described as
mutually exclusive, although some (see Schwarz & Stahlberg, 2003) claim
that both may be factors in producing hindsight bias in real life. There are
important differences between various theoretical accounts within each set
of explanations. Some of these differences are considered below. In addition, the distinction between memory impairment and biased reconstruction hypotheses is not always clear. An example of the difficulty in defining
exactly what is meant by reconstructive approaches in hindsight bias is represented by the ambiguity in interpreting accessibility accounts of hindsight
bias, which some (e.g., Pohl, Eisenhauer, & Hardt, 2003) consider examples
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of biased reconstruction (probably because the models involve reconstructive processes based on separate memory traces), and others (e.g., Schwarz
& Stahlberg, 2003) consider variations of the memory impairment hypothesis (probably capitalizing on the fact that these models accept the existence
of a memory trace for the original estimate, whereas the biased reconstruction approach denies it). Despite the fuzzy boundaries between them,
however, we think the grouping of theoretical accounts into these two broad
categories remains heuristically useful.
MEMORY IMPAIRMENT HYPOTHESES
According to memory impairment hypotheses, which were first advocated
by Fischhoff (1975) for the hindsight effect and Loftus (1975) for the misinformation effect, memory for the original event is modified permanently by
the presentation of new information, which automatically alters or erases
existing memory traces. Fischhoff (1975) suggested that the information
provided by the experimenter about the correct estimate is assimilated to
previous knowledge about the item/event, resulting in an automatic and
permanent alteration of the original memory representation of item-specific
knowledge. The immediate and irreversible assimilation of the new information into one's memory would prevent access and retrieval of the original
estimate. Similarly, for the misinformation effect Loftus (1975; also see Loftus & Hoffman, 1989; Loftus & Loftus, 1980) suggested that post-event information automatically and destructively updates the memory trace of the
original event by overwriting or erasing it, making it no longer available
(Loftus, 1975).
We are aware of only one experiment that was designed to directly test the
memory impairment hypotheses in both hindsight bias and the misinformation effect using comparable procedures. In this study (Pohl & Gawlik,
1995), one group of participants was tested with the hindsight bias paradigm and the other with the misinformation paradigm, and the same numerical items were used as material with both tasks. Participants were asked
to either provide an estimate of some values or to read those values. Then for
some items they were told a new value (outcome or misinformation). Although initial results showed that similar results were obtained with the two
paradigms, a multinomial model of hindsight versus misinformation data
revealed a more complex pattern, indicating that hindsight bias and misinformation are created in part by different processes, but that reconstructive
processes are common to both.
Other variants of the memory-impairment approach locate the origin of
the memory distortion in retrieval, rather than encoding, attributing it to the
relative accessibility of memory traces. The dual memory trace model proposed for hindsight bias, for example, assumes that the bias results from
weighted integration at retrieval of two separate memory traces: one for the
HINDSIGHT BIAS AND FALSE MEMORIES
209
original prediction and one for the outcome information (Hell, Gigerenzer,
Gauggel, Mall, & Miiller, 1988). The relative accessibility of the two traces
depends on the depth and recency of encoding.
Accessibility at retrieval is also the focus of other models proposed both
for hindsight bias and misinformation effects (e.g., Morton, Hammersley, &
Bekerian, 1985; Strack & Mussweiler, 1997; Mussweiler & Strack, 1999). The
common theme in these models is that the effects occur because the new information modifies the activation and accessibility of the original memory,
which thereby becomes less accessible (Bekerian & Bowers 1983; Bowers &
Bekerian, 1984; Christiaansen & Ochalek, 1983).
Nobody has directly addressed the question of whether false autobiographical memories can be the product of processes akin to memory impairment, in spite of the implication of the term "memory implantation," which
is commonly used to describe a number of these effects (e.g., Loftus, 2005).
Arguably, if a new and false memory is implanted, then the process might be
similar to the immediate and irreversible assimilation of the new information into one's memory that has been invoked in the memory impairment
hypothesis.
BIASED RECONSTRUCTION HYPOTHESES
Memory impairment accounts of the misinformation effect were strongly
challenged by McCloskey and Zaragoza (1985) who, using a modified version of the original misinformation paradigm,^ demonstrated that
post-event misinformation is basically a response bias, and does not impair
memory for the original information. The authors proposed a reconstructive
account in which misinformation biases the responses of the subjects who,
for various reasons, cannot remember the original information but do
remember the misleading information.
Although subsequent work on the misinformation effect has shown that
memory impairment might still be responsible for the memory distortions
observed when misleading information is provided at test (e.g.. Belli, 1989),
the hypothesis advanced by McCloskey and Zaragoza (1985) provided the
basis for the development, during the 1990s, of a reconstructive approach
(the biased reconstruction approach) in the field of hindsight bias. The biased reconstruction approach assumes that hindsight bias does not result
1. In the modified procedure used by McCloskey and Zaragoza (1985), both experimental and control participants are required to choose between the old information and a new
answer on the recognition test, with the misleading information absent. If misleading information impairs memory for the original information, then misled subjects should perform more poorly than controls. On the contrary, if the misleading information does not
impair memory for the original information, then the two groups should not differ. In their
study, no significant differences between the two groups were found.
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from memory impairment, but rather from a reconstruction of the original
estimate at retrieval, which occurs when the original estimate is not remembered. In this case, lack of memory needs to be compensated by reconstructive inferential processes that use the outcome information as an anchor
(Erdfelder & Buchner, 1998; Schwarz & Stahlberg, 2003; Stahlberg & Maass,
1998; Werth et al., 2002; Wirunan, Juslin, & Bjorkman, 1998). Considerable
empirical evidence has accumulated confirming assumptions and predictions of the biased reconstruction approach. These data indicate that outcome information biases the reconstruction of the missing original estimate
(see Schwarz & Stahlberg, 2003 for a discussion of this issue).
A biased reconstruction approach has never been proposed specifically to
explain false autobiographical memories. Nonetheless, errors in autobiographical memory are usually explained referring to reconstructive hypotheses (e.g., Conway 1997) that are considered the dominant paradigm in
memory (Schacter, 1999). According to a broad interpretation of this approach, which started with the work of Bartlett (1932), remembering is not
the result of the direct access to a clear memory representation, but depends
on a series of reconstructive processes. These include access to incomplete
memory traces (when present and accessible), which can be episodic or
schematic, and the activation of a series of inferential and decisional processes based on available information and, according to some (Nelson &
Narens, 1994; Koriat, Goldsmith, & Pansky, 2000; Mazzoni & Kirsch, 2002),
on metacognitive evaluations. The relative weighting assigned to these different mental contents determines the degree of accuracy of the memories,
leaving ample room for bias effects.
An approach that includes biased reconstructive processes has been recently proposed by Mazzoni and Kirsch (2002) to account for the effect of
new information on the creation of false autobiographical beliefs (i.e., beliefs
about the occurrence of a personal event, and false autobiographical memories). In the proposed model, memory processes, inferential processes, and
metacognitive judgments interact when people decide whether a target autobiographical event has or has not occurred. According to the model, when
asked to decide whether they had experienced a certain event, participants
first search their memory for good candidates. If a candidate who passes a
preset criterion is found, then the conclusion is that the event has occurred.
If no memory candidates pass the preset criterion, then a series of inferential/decisional processes intervene in deciding whether the event might
have happened, even though no corresponding memory of it is available. In
this case, available information is recruited and examined, and
metacognitive judgments about it are made. This information includes
newly provided information (regardless of whether it is true or false), and
pre-existing factual and autobiographical knowledge (e.g., the autobiographical knowledge base proposed by Conway & Pleydell-Pearce, 2000).
New information is highly influential and biases the final response. The
Mazzoni and Kirsch (2002) model explicitly distinguishes autobiographical
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211
beliefs from memories and considers the relation between the two constructs. It asserts that beliefs about occurrence of an event influence the likelihood of creating a false memory by decreasing the preset memory criterion
and by enhancing the recruitment of corroborating information in memory
and knowledge and their integration into a meaningful whole.
METACOGNITIVE JUDGMENTS
An important aspect of many reconstruction approaches is the role assigned
to metacognitive processes (i.e., processes that involve cognitions about
one's cognitive activities; Nelson & Narens, 1994). Metacognitive judgments
seem to play a role in the types of memory distortion examined here, all
three of which have been found to depend strongly on people's evaluations
of various characteristics of their current cognitive processes and contents.
They influence the hindsight bias effect (e.g., Sanna & Schwarz, 2003,2004;
Pohl, 1998; Ofir & Mazursky, 1997; Werth et al., 2002; Winman et al., 1998),
they can determine the size of the misinformation effect (e.g., Mazzoni, 1998;
O'Sullivan, Howe, & Marche, 1996; Weingardt, Leonesio, & Loftus, 1994),
and they have been shown to be crucial in the acceptance or rejection of various types of false memories (e.g., Schacter, Israel, & Racine, 1999; Strack &
Bless, 1994; Ghetti, 2003). The definition of metacognitive judgments can be
rather broad and include factors that have been well studied in memory research, such as source monitoring, perceived familiarity and fluency, and remember/know judgments, as well as less well-studied factors such as
distinctiveness, memorability and plausibility evaluations. Of these, familiarity/fluency, plausibility, and memorability, will be reviewed here as relatively little studied in hindsight bias, but promising areas for future
investigation. In addition, the potential influence of social variables on
metacognitive judgments will be considered.
Familiarity and Fluency. Familiarity refers to a perceived increased activation of memory representations (memory strength). Familiarity and fluency-based explanations represent a powerful account of memory
distortions, including the formation of false memory. Indeed, attributional
theories have long claimed that misattributing perceived fluency or familiarity creates memory distortions (Jacoby, Kelley, & Dywan, 1989; Kelley &
Jacoby, 1993; Kelley & Jacoby, 1998). If participants are not aware of the reason for the enhanced fluency/familiarity, they can easily misattribute it to
other variables, such as having experienced an event, an event being true or
known or having lasted a long time, etc. More recently, the familiarity
misattribution model has been specifically proposed as a possible explanation of visual hindsight bias (Harley, Carlsen, & Loftus, 2004) and of the creation of false autobiographical memories (Whittlesea & Williams, 2000,
2001a, 2001b; Loftus & Bernstein, 2005). Harley et al. (2004) demonstrated
that visual hindsight bias is due to the misattribution of the enhanced per-
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ceptual fluency obtained when a target stimulus is clearly identified, and
that the bias is partially reduced if participants are aware of the reason of the
enhancedfluency.In the domain of autobiographical memories, Loftus and
Bernstein (2005) claim that rich false memories are usually created by increasing processing requirements (e.g., participants are asked to imagine an
event, to elaborate on some new information, etc). Elaborating the new information (e.g., imagining it) increases the perceived level of familiarity of
the event; in turn this increased familiarity is erroneously attributed to
childhood experience, rather than to the recent elaboration (Loftus &
Bernstein, 2005, p. 110). In a similar vein, a "familiarity plus corroboration"
model proposes that false memories are due to a surreptitiously enhanced
feeling of familiarity of a specific item, which triggers the search for corroborating (and false) memories (Lampinen, Meier, Arnal, & Leding, 2005).
Although initially proposed in a different context, this model can easily
explain how rich false autobiographical memories are created.
Familiarity-based models could also account nicely for the misinformation effect, especially if combined with source monitoring problems (i.e.,
misattributing a mental event to the wrong source; Johnson, Hastroudi, &
Lindsay, 1993). If imagined items, for example, are very vivid and detailed,
monitoring these characteristics can lead to misattributing the items to perceptual sources (items are considered seen instead of imagined). High levels
of perceived familiarity or processing fluency of the misinformation can
trigger the same type of error in source attribution, in which the information
is attributed to the original event instead of to post-event information. This
is not just a bias, but a set of processes in which subjective evaluations of the
status of the information (i.e., metacognitions) guide memory decisions.
Although fluency/familiarity-based models can account for many types
of memory errors, they are only two of several possible types of information,
the evaluation of which can influence memory. Subjectively evaluated item
plausibility and memorability are two other factors that have been explored
in the memory distortion literature.
Plausibility. The subjective (metacognitive) evaluation of event plausibility is crucial in determining not only the type of response (for implausible
events the decision is that they have not happened), but more crucially
whether a false belief and a false memory can be created. Some studies have
found that false memories or beliefs cannot be created when events are considered to be implausible (e.g., Pezdek, Finger, & Hodge, 1997). Others have
demonstrated that subjective plausibility can be modified, and that an increase in perceived plausibility produces an increase in false autobiographical beliefs and memories (e.g., Mazzoni et al., 2001). Recently, it was found
that subjective plausibility predicts response times for responding to questions about autobiographical beliefs, which suggests that the higher the
plausibility, the greater the amount of information evaluated in order to decide whether an event has happened (Mazzoni, in press). Research has
shown that plausibility also affects hindsight bias (Pohl, 1998; Hardt & Pohl,
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213
2003). While subjectively plausible outcomes lead to a strong hindsight bias
effect, subjectively implausible outcomes result in a reduction, elimination,
or reversal of the effect (e.g., see Ofir & Mazursky, 1997; Hoch &
Loewenstein, 1989 for the role of surprise in hindsight bias).
Memorability. Event memorability, which is the subjectively perceived
likelihood of remembering an event, is another type of metacognitive
knowledge that plays a role in the creation of false memories. According to
Strack and Bless (1994), during retrieval, a so-called memorability strategy
can give rise to false memories. When an event is perceived and evaluated as
memorable but no features are accessed in episodic memory, then one concludes that the event was not experienced (and hence did not occur). Bizarre
or salient events, such as being welcom^ed in class by an elephant, are subjectively judged as being highly memorable. In this case, if no relevant information is accessed in episodic memory, then the likely conclusion is that the
event had not happened. The role of the memorability strategy has been
demonstrated in conditions in which only the perceived memorability, but
not the objective likelihood of remembering the event, has been manipulated (e.g., Ghetti, 2003). False memories are more easily produced when an
event is deemed not memorable and more easily rejected when an event is
considered memorable.
Subjectively judged item memorability might also be at play in determining the size of the hindsight bias effect, but the effect would depend on the
accuracy of those judgments. Estimates that are correctly considered to be
highly memorable (and hence are remembered) might be less modifiable
than less memorable ones, and thus the bias would be reduced or eliminated. For example, the reasoning of a potential participant might be: "I can
remember my initial estimate very well. Hence, whatever the correct information, I know what I said before." Conversely, high levels of perceived
memorability might have an opposite effect and produce a larger bias if the
memorability judgment is not accurate and highly memorable estimates are
not remembered. In this case participants would "remember" (or reconstruct) estimates that are closer to the outcome information. This effect
would be similar to that observed in participants who are overconfident (i.e.,
they are certain that they know the height of the Eiffel Tower, but they do not
and provide a wrong estimate), who show greater bias (e.g., Schwarz &
Stahlberg, 2003) because they believe that they already knew the answer.
Social Variables. Metacognitive subjective judgments can be modified by
external information. For this reason, one can predict that social variables—which when referred to memory distortions are sometimes termed
cowitness information (Shaw, Garven, & Wood, 1997), memory conformity
(Wright, Self, & Justice, 2000), or social contagion of memory (Roediger,
Meade, & Bergman, 2001)—would affect the outcome in hindsight bias, misinformation, and false memory creation (Bless & Strack, 1998; Stahlberg,
Maass, & Frey, 1995; Walther & Blank, 2004; for an approach in which
metacognitive and social variables act independently on hindisight bias, see
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Werth et al., 2002). This has been demonstrated in the misinformation paradigm in a number of studies in which pressure to conform (Bregman &
McAllister, 1982), perceived degree of knowledge of the questioner who introduced the misinformation (Smith & Ellsworth, 1987), and answers provided by others (Wright et al., 2000; Wright, Mathews, & Skagerberg, 2005)
affected the degree of acceptance or rejection of the misinformation (i.e., the
overall accuracy of the report).
Walther and Blank (2004) have proposed an interesting theoretical model
in which social and metacognitive variables interact in producing the misinformation effect. Among other metacognitive judgments, plausibility and
saliency of the information are postulated as necessary to moderate the effects of social variables (e.g., information credibility and group size). The interaction between the two sets of variables determines whether socially
induced false information is accepted or rejected.
The effect of social variables on memory has not been systematically explored in the false autobiographical memory arena. However, the fact that
changes in memory are easily obtained when relatives report about events
that had not occurred (Loftus & Pickerell, 1995), when a "clinical psychologist" interprets dreams (Mazzoni et al., 1999), or when people read reports
from authoritative, reliable sources (Mazzoni et al., 2001) converge to indicate that social variables are important in creating rich false memories. Further studies should address not just the influence of single social variables
on memory distortions, but examine more in-depth how social variables
and metacognitive variables interact in the creation of memory errors, as
suggested by the Walther and Blank (2004) model.
CONCLUSIONS
It is proposed here that metacognitive judgments and evaluations represent
an important component in the creation of distorted memories. The importance of taking into account subjective metacognitive judgments has been
underlined in research on the psychology of memory accuracy (Koriat &
Goldsmith, 1998), which stresses the importance of subjective experiences in
determining memory reports and their correspondence with reality. We
agree with Koriat and collaborators' claim that the quality of subjective experience may represent a crucial factor in leading the rememberer to decide
whether to accept a memory as true or reject it as false (Koriat et al., 2000).
Metacognitive evaluations involved in the reconstruction of a memory (or
in the construction of a new memory) can include, but are not limited to,
variables such as fluency, familiarity, memorability, and plausibility.
Whereas the role of perceived familiarity andfluencyjudgments in memory
has been extensively studied, the other variables, for the moment, have received less attention. Nevertheless, they all have been shown to influence to
various degrees the effect that newly provided information has on memory.
Several studies have shown that these subjective evaluations of mental con-
HINDSIGHT BIAS AND FALSE MEMORIES
215
tents control or guide cognitive and attributional processes, which in turn
might distort memory, either by producing an erroneous reconstruction of
an original event or by creating a novel one.
Hindsight bias, misinformation, and more complex false autobiographical memories might all derive from the interaction of mental contents,
metacognitive judgments, and inferential processes. In other words, for all
three paradigms it is possible to claim, borrowing the words of Koriat et al.
(2000), that in remembering, individuals face "the challenge of interpreting
an ambiguous mental record, applying heuristics that are of limited validity,
and engaging in a variety of fallible inferential processes" (p. 513).
This more general reconstructive approach represents a promising direction for future research in all three areas. Fluency- and familiarity-based
models, as well as other metacognitive variables, might provide a clearer
picture of the mechanisms involved in biased reconstructions. Additional
work in this direction might include the direct assessment of the role of perceived fluency of outcome information in verbal hindsight bias and in the
creation of false memories. The role of memorability and plausibility also
represents a promising topic of investigation. They may have the potential
to block the creation of false memories or increase significantly their rejection and block or reverse hindsight bias and misinformation effects. Other
metacognitive factors—for example, the perceived difficulty of the task, and
judgments and attributions about lack of memory—might also moderate
the effect of new information. How social irifluence interacts with these variables is also worth exploring. Direct tests of how social variables affect
metacognitive judgments and attributional decisions could reflect more
closely the processes that intervene in creating memory distortions in
real-life situations.
In this article, we have focused on the similarities among the three types of
memory distortions examined here (see also Bradfield & Wells, 2005;
Brainerd & Reyna, 2002). However, it is equally if not more important to imderstand the crucial differences among them. It might well be that despite
sharing some basic processes (e.g., metacognitive evaluations), different
types of memory distortions are created by different mechanisms (Mazzoni,
2002; Pezdek et al, in press). Future studies more directly comparing hindsight bias and other forms of memory distortions are necessary to better
understand the differences.
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