Using source cues and familiarity cues to resist imagination inflation

Acta Psychologica 120 (2005) 227–242

www.elsevier.com/locate/actpsy

Using source cues and familiarity cues to resistimagination inflation

Stefanie J. Sharman *, Maryanne Garry, Maree Hunt

Victoria University of Wellington, Wellington, New Zealand

Received 6 October 2004; received in revised form 5 April 2005; accepted 6 April 2005

Available online 20 June 2005

Abstract

To investigate whether people can resist imagination inflation—the imagination-induced

increased confidence that fictitious childhood events really happened—we gave them different

types of cues. In a three-stage procedure, participants: (1) rated their confidence that a list of

childhood events had happened to them, (2) imagined some of these events, and (3) made con-

fidence ratings a second time. Subjects received either no cues about the source of the imagined

event, an additional source cue (perspective), an additional familiarity cue (a plausibility ques-

tionnaire), or both cues. Only subjects who had both types of cues resisted imagination infla-

tion. These results suggest that additional cues can sometimes safeguard people from

becoming more confident that fictitious events were genuine experiences.

� 2005 Elsevier B.V. All rights reserved.

PsycINFO Classification: 2343

Keywords: Autobiographical memory; Imagination inflation; Source monitoring

0001-6918/$ - see front matter � 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.actpsy.2005.04.002

* Corresponding author. Present address: School of Psychology, University of New South Wales,

Sydney, NSW 2052 Australia. Tel.: +61 2 9385 3047; fax: +61 2 9385 3641.

E-mail address: [email protected] (S.J. Sharman).

228 S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242

1. Introduction

Asking people to imagine fictitious childhood events can increase their confidence

that the events really happened, an effect called imagination inflation (Garry, Man-

ning, Loftus, & Sherman, 1996; Heaps & Nash, 1999; Paddock et al., 1998; Sharman,Garry, & Beuke, 2004). In the research we present here, we asked whether giving

people certain kinds of information can help them resist imagination inflation.

Research has shown that helping people resist imagination inflation is not as easy

as merely warning them about how it can happen (Landau & Von Glahn, 2004).

Landau and Von Glahn warned subjects that imagining fictitious childhood events

could make them more confident that those events really happened, and although

the warning reduced imagination inflation, it did not eliminate it completely. Landau

and Von Glahn suggested that future research concentrate on attempts to differenti-ate between the two mechanisms thought to drive imagination inflation. We ad-

dressed this focus in the current experiment and investigated whether people given

cues based on the mechanisms behind imagination inflation helped them resist the

confidence-boosting effect. Researchers have amassed evidence suggesting that two

broad mechanisms are responsible for producing imagination inflation: source con-

fusion and familiarity (Garry et al., 1996; Garry & Polaschek, 2000; Goff & Roedi-

ger, 1998). Both of these mechanisms are part of the Source Monitoring Framework

(SMF; Johnson, Hashtroudi, & Lindsay, 1993), which describes how people attri-bute reality to their mental representations.

1.1. Source confusion

According to the SMF, an important way in which people determine the origins

of their memories—that is, whether a memory is of a real event or an internal event,

such as an imagined experience—is by using the characteristics of those memories

(Johnson et al., 1993; Mitchell & Johnson, 2000). Memories from external sourcesgenerally contain more perceptual and sensory details than memories from internal

sources, and people can use these qualitative differences to judge sources (Johnson,

Foley, Suengas, & Raye, 1988; Schooler, Gerhard, & Loftus, 1986). For example,

Johnson et al. (1988) found that externally generated recent memories contained

more details than internally generated recent memories for 16 of the 20 qualitative

characteristics on which these two types of memories differed significantly.

A source confusion account of imagination inflation suggests that people confuse

their memories of imagined events with their memories of real childhood events fortwo reasons. First, source confusionmay occur because imagining fictitious events gen-

erates perceptual and sensory details similar to that of real memories (see Johnson

et al., 1988). Second, source confusion may occur because information about the cog-

nitive processes used to generate images is reduced with repeated imaginings (see also

Finke, Johnson, & Shyi, 1988). Either of these routes alone may increase the risk of

source confusions, and both togethermay play a powerful role in imagination inflation.

Support for this source confusion explanation comes from Thomas, Bulevich, and

Loftus�s (2003) research. They found that subjects who repeatedly imagined fictitious

S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242 229

events showed more imagination inflation than subjects who only imagined the

events once. These results suggest that those individuals who imagined the events

multiple times generated more sensory and perceptual details about them (see also

Lampinen, Odegard, & Bullington, 2003). If so, those extra qualitative details should

have further increased the similarity between imagined and experienced actions caus-ing even more imagination inflation, supporting a source confusion mechanism in

imagination inflation.

However, one curious finding was that Thomas et al.�s (2003) read-only subjects—those who read event statements five times—showed imagination inflation. Although

the level of inflation was not as great as subjects who imagined the fictitious events

five times (18% of responses), many subjects who read the statements five times said

that the imagined events really happened (10% of responses). Such a result cannot be

easily explained by source confusion because the Thomas et al. procedure was de-signed to make it difficult for subjects to generate perceptual and sensory details.

In fact, their subjects had to circle the longest words in each statement to prevent

them from generating mental images. Instead, these results suggest that another

mechanism—one produced by reading the statements repeatedly—has a role in

imagination inflation. Put another way, these results suggest that a familiarity mech-

anism can also contribute to imagination inflation.

1.2. Familiarity

According to the SMF, people can also use the familiarity of memories—instead

of the more specific qualitative details—to judge their source (Johnson et al., 1993;

Mitchell & Johnson, 2000). A familiarity explanation of imagination inflation is

based on Jacoby and colleagues� familiarity misattribution (Jacoby, Kelley, Brown,

& Jasechko, 1989; Jacoby, Woloshyn, & Kelley, 1989). The familiarity of an event

depends on the ease with which it ‘‘pops’’ into mind: the more often an event is expe-

rienced, the more easily and fluently it is processed, and the more easily it comes tomind (Whittlesea, 1993; see also Tversky & Kahneman, 1973). People who are un-

sure whether an event happened may rely on its fluency: the more fluently an event

is processed, the more likely people are to say that they have experienced it (Whit-

tlesea, 1993; see Kelley & Jacoby, 1998, for a review).

A familiarity account of imagination inflation suggests that when people imagine

the target events, their processing of these events becomes more fluent. This increase

in processing fluency can affect people in one of two ways (Whittlesea & Leboe, 2003;

Whittlesea & Williams, 1998, 2000). First, people might compare the increased pro-cessing fluency of the imagined events to the average processing fluency of similar

events. Second, people might compare the increased processing fluency of the imag-

ined events with the processing fluency they expected for those events. This latter

process seems more likely in the imagination inflation procedure because people pre-

fer to use expected fluency rather than average fluency to make judgments, and peo-

ple are more likely to use expected fluency for meaningful stimuli, like the imagined

events (Whittlesea & Leboe, 2000, 2003). Thus, after imagining the fictitious events,

people are surprised at how easily they come to mind at post-test. The consequence,

230 S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242

according to Whittlesea and Williams (2000) is that ‘‘people unconsciously attribute

the unexplained fluency to a prior experience and consciously experience a feeling of

familiarity’’ (p. 547). This familiarity translates into increased confidence that the

childhood events really happened, which is imagination inflation.

Further support for a familiarity account of imagination inflation comes from tworecent studies that showed imagination is not necessary to produce ‘‘imagination’’

inflation (Bernstein, Whittlesea, & Loftus, 2002; Sharman et al., 2004). In both of

these experiments, instead of imagining the childhood events, subjects worked with

text puzzles that required substantial cognitive resources: they solved anagrams or

paraphrased statements containing the events. It is possible that both of these

manipulations increased the processing fluency of the target events, and subjects

misattributed the surprising familiarity at post-test to their childhoods. Overall, these

results show that imagination inflation may also be caused by a discrepancy betweenthe actual and expected processing fluency of the imagined or exposed events (see

also Sharman, Manning, & Garry, 2005, for other non-imagination based inflation).

Taken together, these experiments described above suggest that both source con-

fusion and fluency-based familiarity play a role in imagination inflation. Indeed, it is

not really surprising that both source confusion and familiarity are involved in imag-

ination inflation: people make judgments about the source of their memories by using

either specific, qualitative characteristics of memories, such as perceptual details, or

by using more general features, such as familiarity (Johnson et al., 1993; Johnson& Raye, 1998; Mitchell & Johnson, 2000). For example, task type can determine

which features—specific details or general familiarity—people rely on more to make

their memory judgments (Johnson et al., 1993; Johnson, 1997). More specifically,

people often rely on detailed information about the characteristics of their memories

to make their source monitoring judgments, such as when distinguishing between

imagined and genuine memories of childhood events. By contrast, people typically

rely on more general familiarity information to make judgments in fluency-based

priming tasks, such as when determining the truth of repeated statements. In short,the extent to which people rely on the qualitative details or familiarity of their mem-

ories to make judgments about them, should depend on the type of task they are gi-

ven: source monitoring tasks should encourage people to use more specific details,

whereas repetition tasks should encourage people to use familiarity.

In this experiment, we investigated whether giving people two types of cues would

help them to resist imagination inflation. The source cue was designed to maximise

their reliance on specific qualitative characteristics, while the familiarity cue was de-

signed to maximise their reliance on familiarity. To investigate the separate and com-bined effects of these cues, subjects received either (1) a source cue; (2) a familiarity

cue; (3) both source and familiarity cues, or (4) no cues. We discuss each of these

types of cue in more detail below.

1.3. Cues

Source cue. People use qualitative cues, such as visual details, sounds, and smells

to determine the source of their memories (Johnson et al., 1988). However, in imag-

S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242 231

ination inflation, they may confuse imagined and real childhood memories, a process

which suggests that these qualitative details are not salient enough to alert them that

the imagined events did not really happen. We gave subjects an additional source cue

in the form of a perspective to emphasise the salience of these details and to encour-

age better source monitoring.People typically recall more recent memories from a first-person perspective (how

they see in everyday life), and more distant memories from a third-person perspective

(from another person�s perspective; like watching a movie of themselves) (Lorenz &Neisser, 1985; Nigro & Neisser, 1983). Libby (2003) manipulated perspective in

imagination inflation using a three-stage procedure. In the first session, subjects com-

pleted the Life Events Inventory (LEI; Garry et al., 1996) using one of two different

formats. The LEI contains a list of events such as ‘‘kissed your boyfriend or girl-

friend at school’’ and ‘‘shook hands with the President’’; subjects rate how confidentthey are, on eight-point Likert scales, that they experienced these events. Half the

subjects rated their confidence for events phrased in the first-person: they rated

whether they ‘‘remembered doing’’ events. The other half did the same test with

instructions and events phrased in the third-person: they rated how confident they

were that the events ‘‘happened to them.’’ In a second session, subjects imagined fic-

titious childhood events from a first-person perspective or a third-person perspective.

After a five minute filler activity, they completed the post-test LEI, which was in the

same format as the pre-test LEI.When the LEI and imagination perspectives matched, more imagination inflation

occurred than when they did not match. Libby (2003) hypothesized that her results

fit with a mechanism in which subjects bring to mind the images they generated dur-

ing the imagination phase to decide whether the events really happened at post-test.

When perspectives do not match, people can use that information to decide that their

memory for that event is unreliable. Such a process would leave them unlikely to

confuse their images with real life. In short, perspectives can act as a source cue to

help subjects ward off imagination inflation.In our experiment, we examined whether when people could use perspectives as an

additional source cue to resist imagination inflation, and also whether the combina-

tion of a source cue and a familiarity cue could increase this resistance. At pre-test,

subjects completed an LEI with events worded in the third-person. In the second ses-

sion, one week later, half imagined the childhood events using a third-person per-

spective and half used a first-person perspective. Finally, in the third session, our

subjects completed the post-test LEI with events worded in the third-person.

As Libby (2003) hypothesised, the change in perspectives should act as a source cue,alerting subjects to differences between their imagined memories and their real child-

hood memories. In other words, such a process should encourage their reliance on

source monitoring, which in turn should encourage subjects to rely on the specific

qualitative details of their memories to accurately distinguish between them. The per-

spective cue should give the ‘‘first-person’’ subjects additional qualitative information,

and boost accurate source monitoring. Because the ‘‘first-person’’ subjects should

have an additional source cue to help them resist inflation, Libby�s findings lead us

to predict that the ‘‘third-person’’ subjects would show more imagination inflation.

232 S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242

Recall, however, we also gave half our subjects a familiarity cue, reasoning that

they might be able to rely on it in some circumstances. Here, Libby�s (2003) findingsdo not help us in predicting the role of the familiarity cue, for two reasons. First, she

did not give her subjects a familiarity cue. Second, her subjects completed the post-

test LEI only five minutes after imagining the target events. Thus, regardless ofwhether subjects had imagined those target events in the first or third person perspec-

tives, there is no reason to expect that they would have experienced any perspective-

based differences in familiarity during the test. Therefore, we wondered what would

happen if we also gave half our subjects a familiarity cue: would imaginary third-per-

son subjects also be able to resist imagination inflation when they are alerted to the

familiarity of the target events?

Familiarity cue. When people have an obvious source for their feeling of familiar-

ity, they are less likely to (mis)attribute it to the wrong source (Jacoby, Kelley, et al.,1989; Jacoby & Whitehouse, 1989; Whittlesea, Jacoby, & Girard, 1990). For exam-

ple, Jacoby and Whitehouse�s subjects studied a list of words. During a later recog-

nition test, subjects received each test word immediately preceded by the same word,

a different word, or no word. When the preceding word was presented subliminally,

subjects were more likely to call the new words ‘‘old’’ when the test word and pre-

ceding word matched. However, when the preceding word was presented supralim-

inally, subjects were less likely to call the new words ‘‘old’’ when the two words

matched. These results suggest that when subjects were aware of the source of aword�s familiarity, they were less likely to misattribute it. By a similar rationale, if

our subjects were made aware of the imagined events� increased familiarity they

should be less likely to misattribute this feeling of familiarity to their childhoods,

and should show less imagination inflation.

In our experiment, we used a procedure similar to that of Jacoby and White-

house�s (1989) procedure to make half our subjects more aware of the imagined

events� familiarity at post-test and give them an obvious source to which they could

attribute the feeling. Before filling out the post-test LEI, half our subjects completeda plausibility questionnaire containing exactly the same events as on the LEI. The

other half of our subjects was not alerted to the level of the imagined events� famil-iarity and was not given an obvious source to attribute this feeling; they completed

the plausibility questionnaire after the LEI. We reasoned that a plausibility-rating

task would encourage subjects to rely on the global familiarity of their memories

to make their judgments (Johnson et al., 1993). Thus, rather than evaluating the

qualitative characteristics of their memories, subjects should make their judgments

based on the ease with which the events come to mind. We hypothesized that thequestionnaire would act as an additional familiarity cue by making subjects more

aware of the increased familiarity for imagined events. Subjects who see the target

events on the plausibility questionnaire should be more likely to judge, at post-test

LEI, that the source of the familiarity is the plausibility questionnaire. Thus, we ex-

pected that subjects who completed the plausibility questionnaire before the post-test

LEI would show less imagination inflation. By contrast, we reasoned that subjects

who completed the LEI before the plausibility questionnaire would experience a dis-

crepancy between the actual and expected processing fluency of the imagined events.

S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242 233

These subjects should attribute the resulting feeling of familiarity to their childhoods

and show imagination inflation.

1.4. Summary

We investigated whether people can resist imagination inflation, when given addi-

tional source and familiarity cues. Subjects took part in a three-stage procedure. In

Session 1, they rated their confidence about a list of childhood events using a third-

person format. In Session 2, half our subjects imagined events from a first-person

perspective, generating an additional source cue; the other half imagined them from

a third-person perspective. In Session 3, half our subjects completed a plausibility

questionnaire before the post-test LEI, which was an additional familiarity cue.

The other half completed the plausibility questionnaire after the LEI.

2. Method

2.1. Subjects

One hundred and forty-nine undergraduate psychology students completed all

three sessions in return for course credit.

2.2. Design

The design was a mixed 2 (event type: imagined or not imagined) · 2 (perspective:first-person or third-person) · 2 (post-test order: plausibility questionnaire first or

LEI first) · 2 (time: pre-test or post-test) design. The between-subjects variables wereperspective and post-test order. The within-subjects variables were time and event type.

2.3. Materials and procedure

Subjects took part in three sessions (see Fig. 1).

Session 1. All first year introductory psychology students were given the standard

Life Events Inventory (LEI; Garry et al., 1996) in a third-person format in mass test-

ing. The LEI consisted of 20 events, eight of which were critical target events and two

were ‘‘impossible’’ events, such as ‘‘Played for the All Blacks,’’ that were added to

ensure that subjects were paying attention to the items (Sharman et al., 2004). Thethird-person format was worded so that subjects rated how confident they were that

the events happened to them. Subjects rated their confidence that the events hap-

pened before the age of 10 on an 8-point Likert scale from 1 (definitely did not hap-

pen) to 8 (definitely did happen). Subjects took approximately 5 min to complete the

LEI.

Session 2. Between 2 and 7 weeks after completing the LEI—depending on their

availability—subjects were given the opportunity to participate in a seemingly unre-

lated study about dream control. In groups of between 2 and 15 people, subjects

Fig. 1. Schematic of the procedure. Note: Plaus refers to the Plausibility Questionnaire.

234 S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242

imagined four of the eight target items from the LEI. These targets were identical tothose used in previous imagination inflation research, and were selected because sub-

jects with similar characteristics typically rate their confidence at the ‘‘definitely did

not happen’’ end of the scale (Garry et al., 1996; Sharman et al., 2004; Sharman

et al., 2005). Target events were counterbalanced so that each event was imagined

and not imagined in every position equally often.

Each subject received a booklet containing the four events to be imagined and the

point of view from which to imagine the events. They were told that they would be

using the events in the booklet to practice an imagination-based dream control tech-nique. The first page of the booklet defined the point of view subjects should use to

imagine the events. Half the subjects imagined the events from a first-person perspec-

tive and the other half from a third-person perspective, as described below.

Subjects who imagined the events from a first-person perspective were told:When asked to imagine the episode from your own perspective, please imaginethe event as if you were watching it from your own point of view, out of yourfirst-person perspective, as you do in everyday life.Subjects who imagined the events from a third-person perspective were told:When asked to imagine the event from a third-person perspective, please imag-ine the event as though you were a bystander and could see yourself doingthings in the event. Imagine yourself from an outside perspective, as thoughyou were watching a movie of yourself.

Subjects were asked to make their imagined scenes as complete, vivid and realistic

as possible. They were asked to include familiar places, people and events from their

own life to help make the scenario more vivid and real.

S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242 235

After imagining each event for 1 min, subjects spent 3 min drawing the events to

ensure that they had been actively imagining them. At the end of the session—in

keeping with the dream control cover story—subjects were given a bogus event to

dream about (getting stuck in a tree), and were instructed to imagine it before going

to sleep every night.Session 3. One week later, subjects returned under the guise of evaluating the

dream control technique they had been using. They were asked to complete several

bogus tests about perceptual ability and dreaming ability, and the post-test LEI was

hidden among these tests. Subjects also completed a plausibility questionnaire. The

plausibility questionnaire consisted of the same events as the LEI, and subjects rated

‘‘how plausible it is that the typical New Zealander, who is about your age, had cer-

tain childhood experiences by age 10.’’ The ratings were made on a Likert scale from

1 (not at all plausible) to 8 (very plausible). Half our subjects completed the plausibil-ity questionnaire immediately before the post-test LEI, and half completed the post-

test LEI before the plausibility questionnaire. To prevent subjects connecting the

LEI and plausibility scale items with those presented during the mass testing session,

the measures were presented using a completely different layout. All subjects were

debriefed at the end of the session.

3. Results and discussion

Fourteen subjects failed to rate all of the items on the LEI and seven incorrectly

answered an impossible item. Their data were removed from the analysis, leaving 128

subjects. At debriefing, most subjects expressed surprise about the true nature of the

study, suggesting they had believed the study was about dream control.

Before examining whether source and familiarity cues helped subjects resist imag-

ination inflation, we determined whether simply giving subjects event statements

twice at post-test increased the familiarity of those events. The ‘‘truth effect’’ predictsthat subjects who received the LEI before the plausibility questionnaire should give

higher plausibility ratings than subjects who received the plausibility questionnaire

first (Arkes, Hackett, & Boehm, 1989; Hasher, Goldstein, & Toppino, 1977). The

truth effect is thought to occur because repeated statements are processed more flu-

ently than non-repeated statements, and people attribute the increased fluency to

validity. In our experiment, such a pattern of results would indicate that the plausi-

bility questionnaire increased the familiarity of the repeated events. Indeed, we found

that subjects who received the LEI before the plausibility questionnaire gave higherplausibility ratings for the not imagined events (M = 5.47, SD = 1.03) than subjects

who received the plausibility questionnaire first (M = 4.96, SD = 1.03),

F(1,123) = 8.59, p = .01, partial g2 = .06. Perspective did not have any effect on sub-

jects� plausibility ratings, F(1,123) = 1.58, ns, nor did the interaction between

perspective and post-test order, F(1,123) = 1.11, ns. These results suggest that expos-

ing subjects to event statements twice increased the processing fluency of those

events, and encouraged subjects to rely on the subsequent feeling of familiarity

to make plausibility ratings. In short, this finding fits with our prediction that the

Table 1

Proportion of subjects whose confidence increased

Imagined Not imagined

Perspective

First-person 0.46 (0.19) 0.60 (0.10)

Third-person 0.59 (0.08) 0.50 (0.08)

Post-test order

Plausibility questionnaire first 0.41 (0.14) 0.54 (0.13)

LEI first 0.64 (0.05) 0.55 (0.06)

Note: Standard deviations are shown in parentheses.

236 S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242

plausibility questionnaire should encourage subjects to rely on familiarity to make

their judgments.

We now turn to our main research question: what information helps people to re-

sist imagination inflation? In line with the recommendations by Garry, Sharman,

Wade, Hunt, and Smith (2001), we examined imagination inflation by calculating

the proportion of subjects whose confidence increased for imagined events compared

to not imagined events.1 Table 1 shows the proportion of subjects whose confidence

inflated for imagined and not imagined events according to perspective (top half) andpost-test order (lower half). The top half of Table 1 shows that subjects who imag-

ined the events from a third person perspective showed imagination inflation, while

subjects who imagined the events from a first person perspective did not show imag-

ination inflation; a 2 (imagination) · 2 (perspective) · 2 (post-test order) repeated

measures ANOVA revealed a significant interaction between perspective and imag-

ination, F(1,28) = 34.03, p < .01, partial g2 = .55. This pattern of results suggests that

subjects can capitalize on perspective to make more accurate source judgments, and

replicates Libby�s (2003) finding that subjects who imagined the critical events usingthe same perspective as they used to complete the LEI showed greater imagination

inflation.

Did the familiarity cue have a similar effect on imagination inflation? The lower

half of Table 1 shows that only subjects who completed the post-test LEI before

the plausibility questionnaire showed imagination inflation, while subjects who com-

pleted the plausibility questionnaire first did not show imagination inflation. In other

words, this interaction between imagination and post-test order was significant,

F(1,28) = 31.31, p < .01, partial g2 = .53. These results suggest that subjects givenan additional familiarity cue in the form of a plausibility questionnaire were able

to use the cue to resist imagination inflation.

1 Garry et al. (2001) discussed some of the statistical and conceptual problems associated with analyzing

imagination inflation data. In particular, they noted that ANOVAs conducted on mean change scores are

not always appropriate because imagination inflation data are typically skewed towards the low end of the

confidence scale at pre-test, and different events have different amounts of variance around the mean at

pre-test and post-test. They recommended the use of an analysis that treats events as cases; that is, looking

at the proportion of subjects whose confidence increased according to whether or not they imagined the

critical events.

0

0.2

0.4

0.6

0.8

First person Third person First person Third person

Prop

ortio

n of

par

ticip

ants

ImaginedNot imagined

LEI first Plausibility questionnaire first

Fig. 2. Proportion of subjects whose confidence increased for imagined and not imagined events. Note:

The error bars represent the standard error of the mean.

S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242 237

However, the pattern of results changes slightly when we look at the combined

effect of the perspective and familiarity cues. The left hand side of Fig. 2 shows thatwhen subjects completed the LEI first, perspective did not matter. That is, subjects

showed imagination inflation regardless of whether they imagined the events from

a first or third-person perspective. However, the right hand side of Fig. 2 shows that

when subjects completed the plausibility questionnaire first, they showed imagina-

tion inflation only when they used a third-person perspective. In fact, subjects

who imagined the events from a first-person perspective showed imagination defla-

tion. This three-way interaction between imagination, post-test order, and perspec-

tive was significant, F(1,28) = 16.58, p < .05, partial g2 = .37. Follow-up pairedt-tests confirmed that all subjects showed imagination inflation, t(7) = 2.37–5.66,

all ps < .05, fs = 0.82–2.70, apart from first-person plausibility subjects who showed

imagination deflation, t(7) = 5.55, p < .05.

Neither imagination nor perspective alone had a significant effect on subjects� con-fidence, Fs(1,28) = 0.71–0.75, ps > .39, both partial g2 = .03. There was a trend for

third-person subjects to show more inflation than first-person subjects when they

completed the plausibility questionnaire first. However, this interaction between

post-test order and perspective did not reach statistical significance, and was qualifiedby the above three-way interaction with imagination, F(1,28) = 3.22, p = .08, partial

g2 = .10. Although imagination and perspective had no effect on confidence, the order

in which subjects completed the questionnaires at post-test did. Subjects who com-

pleted the LEI first gave higher confidence ratings overall than subjects who com-

pleted the plausibility questionnaire first, F(1,28) = 40.97, p < .01, partial g2 = .59.

238 S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242

Considered together, our results suggest that subjects can use an additional source

cue (perspective) to resist imagination inflation when they also have an additional

familiarity cue (the plausibility questionnaire). When subjects have only one cue

or no cues, they show imagination inflation.

Why should imagining the fictitious childhood events from a first-person perspec-tive and completing a plausibility questionnaire help people resist imagination infla-

tion? In a familiarity account of imagination inflation, imagining the fictitious events

should have increased their processing fluency and made them feel more familiar to

subjects. Subjects who completed the LEI before the plausibility questionnaire

should not have been alerted to their familiar feeling, and therefore showed imagina-

tion inflation. By contrast, subjects who completed the plausibility questionnaire be-

fore the post-test LEI should have been more likely to be alerted to their familiar

feeling, and may have wondered about its source. First-person/plausibility subjectswho had an additional perspective cue may have subsequently been able to use this

cue to realize that they had simply imagined the events. As a result, they did not

attribute these events to their childhoods, and did not show imagination inflation.

By contrast, third-person/plausibility subjects who did not have the additional per-

spective cue might not have been able to reject the fictitious events so easily.

Although they should have been alerted to the familiarity of the imagined events,

the cue was not enough for them to resist imagination inflation.

Not only did first-person/plausibility subjects resist imagination inflation, theyactually became less confident that the imagined events really happened. It is possi-

ble that first-person/plausibility subjects used the source and familiarity cues to

recollect the imagination exercise, and knew that they had simply imagined the

events. If so, at post-test they should have rated the target events at the ‘‘definitely

did not happen’’ end of the scale. If subjects� post-test ratings were lower than their

pre-test ratings, it could account for our imagination deflation pattern of results.

Our finding that people given source and familiarity cues could resist imagination

inflation fits with similar research in the recognition literature. The literature showsthat subjects are more likely to rely on the familiarity of an event when they are un-

able to recall the true source of that familiarity (Jacoby & Whitehouse, 1989; Jacoby,

Kelley, et al., 1989; Jacoby, Woloshyn, et al., 1989). For example, Jacoby, Woloshyn

and Kelley�s subjects read aloud a list of nonfamous names in the first phase of the

study. Subjects were then told that all the names they had read were nonfamous. In

phase 2, subjects were given a fame judgment test, which contained old nonfamous

names from the first phase as well as new nonfamous and famous names. Half the

subjects completed this test under conditions of divided attention (listening for par-ticular sequences of numbers) and half completed it with full attention. Subjects were

more likely to show the false fame effect—that is, call old nonfamous names fa-

mous—if their attention was divided at test. These results suggest that repeating

the nonfamous names made their processing more fluent and made them feel more

familiar, and subjects used this familiarity to judge fame. However, when subjects

had information about the source of the familiarity—that is, when they completed

the test with full attention and could recollect the nonfamous names from the first

phase—they were less likely to misattribute this familiarity. Similarly, when our

S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242 239

first-person/plausibility subjects had information about the source of the imagined

events and could recollect the imagination exercise, they were less likely to misattrib-

ute the familiarity and qualitative details generated by imagining the fictitious events

to their childhoods.

Our results are also consistent with Libby�s (2003) results. Recall that her subjectsimagined the fictitious events and completed the post-test LEI five minutes later.

This relatively short delay between the imagination exercise and the LEI should have

made the target events feel familiar at post-test. Subjects should have been able to

use this familiarity in conjunction with the perspective information they had to resist

imagination inflation. Similarly, in our experiment, completing the plausibility ques-

tionnaire immediately before the post-test LEI should have made the target events

feel familiar at post-test for our first-person/plausibility subjects. First-person/plau-

sibility subjects should have been able to use this familiarity in conjunction with theperspective information to resist imagination inflation.

Our results also fit with those in a related memory paradigm: the misinformation

effect (Belli, 1989; Loftus, Miller, & Burns, 1978; Vornik, Sharman, & Garry, 2003).2

The misinformation effect occurs when subjects are exposed to misleading informa-

tion after experiencing an event. Subjects are less accurate at recalling information

targeted by the misleading information than by neutral information. In our experi-

ment, subjects can be said to have generated misleading post-event information when

they imagine the fictitious childhood events. This post-event information should in-crease their confidence these events happened, and decrease their recall accuracy for

the original events. Consequently, it follows that the many manipulations that de-

crease the size of the misinformation effect—such as increasing individuals� abilitiesto discriminate between the original information and the post-event information

(Lindsay, 1990; Tousignant, Hall, & Loftus, 1986)—may also reduce the size of

imagination inflation. Indeed, our results show that when we give people cues to help

them discriminate between the imagined events and their real childhood events, they

are less likely to show imagination inflation. Future research could further manipu-late the differences between the original event (childhood memories) and the imag-

ined events (post-event information) on people�s ability to resist imagination

inflation.

Theoretically, our results are important because they add to the growing number

of studies that suggest both increased processing fluency and a source confusion

underlie imagination inflation (Garry et al., 1996; Goff & Roediger, 1998; Libby,

2003; Thomas et al., 2003). Indeed, recent research has shown that many types of

exposure to fictitious events can increase their processing fluency—through explain-ing, paraphrasing, or solving anagrams (Bernstein et al., 2002; Sharman et al., 2004;

Sharman et al., 2005). Once this processing fluency has increased and subjects expe-

rience a source confusion, their beliefs about the past may change. This increase in

confidence can be the first step down the road to a false memory (Hyman & Kleinkn-

echt, 1999; Mazzoni, Loftus, & Kirsch, 2001). In particular, our results suggest that

2 We thank an anonymous reviewer for pointing out this parallel.

240 S.J. Sharman et al. / Acta Psychologica 120 (2005) 227–242

not only do these mechanisms play a role in imagination inflation, they can also help

people to resist imagination inflation. In fact, our research shows the importance of

the combined effort of both mechanisms: only when individuals had both a familiar-

ity and a source cue could they resist changing their beliefs about the past.

Practically, our results are important because they show that though it is relativelyeasy to increase people�s confidence that an event really happened, it is just as easy toprevent the increase from happening. When people have extra information about the

source of an event�s familiarity, they are less likely to misattribute that familiarity

than people who do not have such information. This additional source and familiar-

ity information could be particularly useful in the context of therapy. For example,

therapists who use guided imagery could help the client make the source of imagined

information distinct so this information is not confused with real events. Indeed,

Arbuthnott, Arbuthnott, and Rossiter (2001) warn that ‘‘clients not. . .use imageryexperience as the only source of information for deciding on their actions’’ (p.

130). Specifically, clients should have additional source and familiarity cues to pre-

vent them confusing experiences they have only imagined with real life events.

Acknowledgments

The authors wish to thank Dan Bernstein and two anonymous reviewers for com-ments on an earlier draft of this manuscript.

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