Memory quality and misinformation for peripheral and ...

lAlgal and Cii1l1in%gical P.fJ'ch%gy (1998), 3, 273-286

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© 1998 The British Psychological Society

Memory quality and misinformation for peripheral and central objects Daniel B. Wright* and Joanne N. Stroud Department oj Experimental P.rycholo!!J, Universi!y oj Btisto~ 8 Woodland Road, Bristol BJ8 1

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UK

Purpose. The quality of memories after the presentation of misinformation was explored. Three different types of stimuli were used: a peripheral object, a characteristic of a (different) peripheral object and a central detail. These were chos!,!n in orde~ to achieve different levels of the misinformation effect. Methods. One hundred and eight university students were shown a computer displayed picture sequence of a shoplifting incident. They were then misled abaut certain aspects. Memory was assessed by forced-choice recognition, 'rememLer'/ 'know' judgments and reaction times. Results. Participants often reported 'remembering' Plis.information for the peripheral object and the characteristic. 'Remember' responses were also associated with the fastest reaction times. Conclusions. Misinformation can make people remember errant information. Implications for eyewitness testimony are discussed.

Misinformation research has demonstrated that a person's memory for an event may be altered by information encountered after the event. In" a series of studies in the 1970s, Loftus and colleagues (for example, Loftus, 1975; Loftus, Miller & Burns, 1978; Loftus & Palmer, 1974) gave people misleading information, in the form of biasing questions and/qr errant event descriptions. They found that these people were more likely to report 'the misleading post-event information, or misinformation, than were controls who were not exposed to the biasing information. For example, in the original presentation of a crime scene there might be a Coke can on a cluttered desk, but it is referred to as a 7-Up can in a misleading post-event narrative. At testing, many people report that a 7-Up can was on the desk. This research, and literally hundreds of latter studies, demonstrate beyond all doubt that presenting contradictory information affects memory reports of a previously seen event. These findings are critical for evaluating eyewitness testimony since during the time between a crime and testimony-in a police station or in a court of law-witnesses may encounter much potentially biasing information. *Requests for: reprints.

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Since the 1970s there have been two developments of relevance to the misinformation effect. The first is trying to why misinformation affects memory reports. In what has become known as the standard testing procedure, used in many of the· original misinformation participants were asked to choose the original information, Coke in the example above, and the m1Sln,tOJrm:atH)n, 7-Up. In an important paper, McCloskey & Zaragoza (1985) asked people to choose' between the original information and a foil which had not been presented. They found misled and control participants responded approximately as often with the original information. More recently, Windschltl, McCarthy & Winfrey (1992) used this modified testing procedure and found that a misinformation effect does occur) but only with longer elapsed times. In a meta-analysis of studies using this modified procedure, Payne, Toglia & Anastasi (1994) also found this. In the present study we are not directly concerned with why the misinformation effect occurs, but with the qualities of memories that result from misinforma tion. The second development is of more direct relevance. There is a growing interest by memory researchers, in general, in more than just the memory responses. This, includes response times, confidence ratings, identifying the source of a memory and introspecting about conscious awareness. These are all relevant to the misinformation paradigm. In this paper, we briefly review relevant misinformation research that goes beyond simply asking the person for a single response. By going further, these studies increase our understanding of misinformation effects. We then report our study which uses Tulving's (1985) 'remember' versus 'know' distinction.

Misinformation research: Delving deeper into the memory That misinformation affects reports is undisputed. However, there are many possible explanations for why it does. Several authors have examined different' aspects of the memories to help tease apart these and have used i variety of methods Wright, 1996, for review). These include changing the order of the items at (Bekerian & Bowers, 1983), people bet on their responses (Toland, 1990, as reported in Weingardt, Toland & Loftus, 1994), giving some kind of about the misinformation & Ochalek, 1983; 1982; Wright, 1993), having 'yes'/'no' judgments (Belli, 1989), allowing people a second guess (Loftus, 1979; Wright, Varley & 1996), and not offering the misinformation as an alternative (McCloskey & Zaragoza, 1985). This is an important area of research for understanding basic processing. However, many lawyers, judges and jurors (not to mention mental health professionals) are more concerned with what memories are like which have been created, in part, by misinformation. The studies most relevant for the present purposes are where the researchers gather information in addition to the memory report. In almost all misinformation studies, participants are told to report what they remember from the original presentation. The first set of studies we discuss go further, forcing participants to decide the source of their memories. Zaragoza & I condition and memory response (LX\2) 6.75>p = .03). This marginally significant interaction is due to the misled people who gave the incorrect answer (the misinformation), giving more remember and know responses than any of the other groups. These analyses were repeated with memory quality collapsed into remember or know versus guessing. The effect of being misled on this was still highly significant (LX\l) = 12.80, p < .001), the effect of being correct was still not significant (LX\1) 0.38, P .54), and the interaction was still in the 'marginal range' (LX2(1) 3.49, P = .06). Descriptively~ it is important to note that a quarter of the misled people who responded with the misinformation 'remembered' it and less than half were 'guessing'. '

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Table 3. The frequencies (a,nd percentages) of different memory qualities for the central object (what was stolen) Condition and responses lYIisled

Control

Remember Know Guess

Incorrect

Correct (N=53)

Incorrect (N=4)

Correct (N=50)

1 (100)

43 (81) 9 (17)

1 (25) 3 (75)

35 (70)

14 (28) 1 (2)

1 (2)

Table 4. The frequencies (and percentages) of different memory qualities for the continuous characteristics (the colour of a bystander's shirt) Condition and responses lYfisled

Control Incorrect (N=31) Remember Know Guess

Correct (N=23)

Incorrect (N=46)

Correct (N=8)

3 (13) 20 (87)

14 (30) 9 (20) 23 (50)

2 (25) 6 (75)

1 (3) 30 (97)

With the central item, we expected most of the partiClpants, regardless of whether misinformation was presented, to respond with the correct response. This is what we observed (see Table 1). Our interest was in whether presenting the misinformation affected the reported memory quality. Table 3 shows that most people 'remembered' the original item. Running a similar series of loglinear models, as we did for the peripheral item, becomes difficult because of the small number of people giving the misinformation. Therefore, we collapsed over whether people were correct or not) and combined know with guess responses. The model leaving out just the association between memory quality and being shown misinformation for this item yielded LX2 (1) - 3.12 (p = .08). This marginally significant difference is in the predicted direction, misinformation lowering the number of 'rememberers) . The continuous characteristic, the colour of the shirt, was not central. Table 4 gives the frequencies and percentages for memory guality broken down by condition and whether the person was correct. Only 8 of the 54 misinformed people reported the colour they had originally seen. Due to this, we compared the memory quality of those misinformed with those not presented with

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Table 5. The means of the logged reaction times, their 95 per cent confidence intervals and the cell frequencies for misled and control items, broken down by whether the person gave the correct answer or not Condition and responses Control

Discrete Object Central Object Continuous Object

Misled

Incorrect

Correct

Incorrect

Correct

1.79 ±0.16

1.54 ± 0.16

1.72 ± 0.15

1.74± 0.28

(N=23)

, (N=29) 1.08 ± 0.08 (N=53) 1.88 ± 0.14 (N=23)

(N=41)

(N=15)

1.69 ± 1.04

1.16 ± 0.13

1.10

(N=l) 1.95 ± 0.12

(N=31)

(N=4)

(N=50)

1.68 ± 0.13

1.74 ± 0.20

(N=46)

(N=8)

misinformation, collapsing over accuracy. Overall there are differences between the conditions (I . . X\2) 23.96, P < .001; comparing guess vs. other response: LX;\l) = 22.58, p< .001). Like the analysis of the peripheral discrete object, these figures show that misinformation acceptance can lead to a substantial number of people 'remembering' and 'knowing' the misinformation. About a quarter of the misled people 'remembered'.

=

Speed

of responding

Our choice of critical stimuli, coupled with participants' reported memory qualities, allows us to examine some particular comparisons about the way in which response times relate to misleading people. Because misleading people affected accuracy (Table 1) and self-reported memory quality (Tables 2-4), the·effects are orthogonal. We focus on the reaction time separately for these. The reaction times were highly skewed. Each was truncated at 20 s (only two times, in total, were above 20 s) and then the natural logarithms were taken. This greatly reduced the skew. The means for the conditions by accuracy are shown in Table 5. In reading this table it is important to take into account. the cell frequencies. We begin by comparing response times for items where people were mis1ed with the control items (collapsed over accuracy and memory quality). The means were non-significant fat the kitchen object (M = 1.65 (SE .06) for control, M = 1.73 (SE .07) for misled, 1(106) .90, P = .37) and for the article stolen (M 1.08 (SE .04) for control, M 1.20 (SE .07) for misled, 1(106) 1.55, P .13). However, the times for the control condition for the bystander's shirt colour were significantly longer than for the misled condition (M 1.92 (SE .04) for control, M 1.69 (SE .06) for misled, t(106) 3.22,p .002). It is worth noting that the time for the control condition is particularly long compared with the other conditions for the other items. We looked also at the relationship between accuracy

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=

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1 Daniel B. Wright and Joanne N. Stroud

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Remember

~

o

Know Guess

Kitchen Object Object Stolen

Shirt Colour

Figure 1. The mean logged reaction times and their 95% confidence intervals for each object and each memory quality response.

and response time. None of the differences were significant. 1 We also looked at interactions between condition and accuracy on response times. None of these were statistically significant. Next, we examined how times varied depending on memory quality for the three items. Figure 1 shows the means and 95 per cent confidence intervals for the logged reaction times for the three critical items. For the discrete item the overall difference was (F(2,105) 4.40,p = .01, MSE .19) and Scheffe tests showed this was to a significant difference between the guess and remember responses. There were no significant differences for the central object (only two people guessed, so the reaction time estimate for these is unreliable). The reaction times for the continuous item showed a similar pattern to discrete object (F(2,105) 10.38, p< .001, MSE .12) with the Scheffe tests showing remember different from both guess and know.

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=

=

Discussion After witnessing a criminal activity, and before reporting a memory to a police investigator or in a court of law, people are going to encounter much information. lIt is perhaps worth noting that the mean 1.12 (SE .04) for the correct responses. Its depends on the assumptions and tests used. Given that N = 5 in one condition, we chose to use the more conse1'Yative statistic.

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They are likely to talk with friends and family about their experience, and possibly even other witnesses. They will also think about the event and their memory of it. The integration of the memory system with our processing of stereotypes, of filling in inferential details as remembered, and allowing any biasing external information into the memorial judgments are all well documented. The result of these effects, that- the videotape metaphor of memory is wrong, has been poignandy argued in law courts by cognitive psychologists to try to errant folk notions of memory (for example, see Loftus, 1986). One of the best demonstrations of the reconstructive nature of memory is the misinformation effect. It demonstrates how information from other sources infiltrates our memory system. Much of the misinformation research has shown under what conditions people are likely to be misled. We used this information, in particular that more people are misled for peripheral items than central ones, so that we could explore what post-event memories are like in different situations. The first was when the original item is not well encoded. The person accepts the information s/he receives, or fills in what slhe expects. The second is when the item is much more centraL As expected) fewer people were misled by our narrative. Out qu.estion was, does the misinformation plant a seed of doubt which is evident in the reported memory qualities and reaction times? For the first situation, the peripheral information is not well encoded, so the participant, or a witness, has little reason to doubt the post-event information. As Loftus (1993, p. 530) argues, 'the new information invades us, like a Trojan horse, precisely because we do not detect its influence'. About 80 per cent of the people misled on peripheral items in this study accepted the misinformation because, without a good memory for the original information, they were unaware that they were being misled. Almost half of these were simply guessing. This might correspond to them having some vague notion of seeing the item somewhere, but not 'knowing' it or 'remembering' it. Some participants said that they 'knew' it was the answer. This may be misplaced trust in the experimenter when the participant has no memory for the original. It is worrying that nearly 30 per cent of these people 'remembered' the misinformation. For these people, the misinformation has become part of their memory. It could be argued that altering a trivial aspect of the memory presents few forensic problems. However, often the details that may seem irrelevant at encoding can become central to the investigation: what was the colour of a parked car, later to be used in a child abduction? Other details are minute on their own but can be used by investigators to piece together criminal profiles. The data presented here offer another worrying forensic implication. It is difficult to conceive of how having a blender rather than a coffee-maker in a kitchen will directly influence criminal investigation. However, Bell & Loftus (1989) have found reporting details can increase the weight jurors give to the overall testimony of the witness. A police investigator could innocendy describe some minute and uncontested detail of a murder scene, possibly in order to help cue the witness to recall substantial aspects, and this could influence the overall credibility placed in the witness's testimony. The investigator might not be suggesting errant information) but it could still affect the recall. .

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Previous research (Loftus. et al., 1989) found that misled participants who reported the misinformation did so quickly. Overall, this is what we found for the peripheral items. However, here the 'remember' responses were much more common for the misled pa-rticipants (Tables 2 and 4). We examined response times broken down by condition and memory quality. It was found that 'remembering' was associated with the fastest reaction times. Because in studies with peripheral items it is likely that' more misled than control people will 'remember', overall, misled people's times will be shorter. The second situation is where the misinformation concerns a central item. Here, over 90 per cent of people reported the original information. Our interest was in whether the misinformation planted a seed of doubt which affected memory quality. There were no statistically significant differences between those people reporting the original information in the control conclition and those in the misled condition. The results were, however, in the expected direction. There was a drop from approximately 80 per cent 'remembering' to 70 per cent. Perhaps a single errant suggestion in a short narrative is not enough to implant a seed of doubt strong enough to be detectable (statistically) with the sample size used. Perhaps, also, a is-minute delay was not enough elapsed time to allow the original memory to decay to the point where it could be manipulated. These questions are clearly also important for the recovered memory debate, in which the therapy can last years and it is often decades since the alleged events occurred. Similarly, repeated questioning by a police investigator is likely to have more impact than a brief narrative. Misinformation research has been one of the most debated topics of applied memory research and the results have influenced theories of memory. It has been a central aspect of eyewitness testimony research and was a focus of debate on expert testimony about whether eyewitness memory should be accepted (see Loftus, 1986; McCloskey & Zaragoza, 1985) for viewpoints; see Falgman, 199 Sj for discussion given recent legal developments). It is important to understand what misinformed memories are like, both for advancing our knowledge of memory and for assisting in legal procedures.

Acknowledgements We would like to thank Hamid Rehman and Marie-Claude Gervais for acting in the shoplifting sequence, John Gardiner and the rest of the Cognitive Workshop at City University for useful discussion, and John Fildes for writing the computer program. Thanks also to Elizabeth Loftus and an anonymous reviewer for helpful comments on a previous draft. We ate grateful to the British Academy who funded this study through a research grant to the first author, and for a Post-Doctoral Research Fellowship to the first author, and to the ESRC for funding the second author (R004296344244). An earHer version of this paper was presented at the International Conference on Memory, Padua, Italy, 1996.

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