System variables in eyewitness identification: Control experiments and photospread evaluation

Transcription

1 lapanese Psychological Research Volume 3R. No. I Special Issue: Eyewirness Te.itimony System variables in eyewitness identification: Control experiments and photospread evaluation KAORU KUROSAWA Department of Psychology, Faculty of Letters, Chiba University, Yayoi-cho, Inage-ku, Chiba 263, Japan Abstract: An incident was staged in front of approximately 140 college students Three months later, 48 of them tried to identify the person of the incident (the target) in a nineperson photospread (Experiment 1) Assisted with a verbal description of the target, 77 less confident students similarly tried to identify him (Experiment 2) Additionally, 69 students from another class tried to choose the target with the verbal description only (Experiment 3 a mock-witness control experiment) Results of Experiment 1 showed that although more than half of the participants correctly identified the target, a similarly high proportion of control participants falsely identified a specific foil as the target. In the three experiments. correct and false identification patterns were similar, and the variables of target presence and distracter similarity independently affected probability estimates for selected photographs to be the target s The implications for actual eyewitness identification are discussed Key words: eyewitness identification, false identification, photospread, blank lineup control, mock-witness control,- Eyewitness testimony in general, and identification of a suspect as the culprit in particular, is crucial in determining the outcome of a criminal trial. In the United States, eyewitness error is probably the single largest factor leading to wrongful convictions (Wells, 1993). Not only prevention and minimization of false identification and conviction, but also correct identification and punishment of genuine criminals are in society s best interest (Loftus, 1993). In this article, some of the factors that affect eyewitness performance are experimentally examined. False identifications occur with surprising frequency in staged-crime experiments, and since false identification rates seem to vary systematically as a function of many factors (Wells, 1993), we should be asking what factors influence and determine them. In the context of eyewitness accuracy and factors affecting it, control conditions are crucially important, but not many early studies seem to have included a proper control group. Some studies merely demonstrated that false identification rates could be surprisingly high (Loftus, 1993), but otherwise proved or tested almost nothing. In early research, false identification rates were computed misleadingly as the ratio of misidentifications of distracters, who were known innocents, to the total identification attempts. However, false identification should mean the cases in which an innocent suspect is identified (Wells, 1993). Therefore, estimation of the false identification rate requires a control group. In the current research, the target in a control lineup was replaced by a special distracter, or foil. The foil is specifically designated as the innocent suspect, and foil Part of this article was presented at the 58th Annual Convention of the Japanese Psychological Association, at Nihon University, in October 1994 The author wishes to thank the students who assisted in the studies Japanese Psychological Association Published by Blackwell Publishers Ltd, 108 Cowley Road, Oxford OX4 ljf, UK and 238 Main Street, Cambridge, MA02142, USA

2 26 K. Kurosawa identification analogously constitutes false identification. The first purpose of this article is to demonstrate the utility of a foil lineup for estimation of false identification rate as well as evaluation of photospreads. The comparison of target correct identification and foil false identification rates can be an index of identification accuracy. Accuracy and confidence Loftus (1993) says that false identifications that are made with a high degree of certainty could be especially problematic. Naturally they are highly persuasive (e.g., see Wells, Ferguson, & Lindsay, 1981), because people typically believe that the more confident they are about their memory, the more likely it is to be accurate. Although postdecision confidence is more likely to correlate highly with accuracy than predecision confidence (Perfect, Watson, & Wagstaff, 1993; Sporer, 1992,1993), and withinsubject correlations might be higher than between-subject ones (Perfect et al., 1993; but see also, Smith, Kassin, & Ellsworth, 1989), most researchers seem to agree that the correlations between them are generally not very high. The correlation may become higher if the data from only choosers (who select a person from a lineup or photospread, rather than identifying no one) are used (Sporer, 1992, 1993) and, further, the correlation may differ between accurate and inaccurate choosers (Wells & Lindsay, 1985). The second purpose of the current research is to investigate the relationship between identification accuracy and eyewitness certainty in the context of the factors just mentioned. Estimator and system variables As Wells explains (1993), many factors affect identification accuracy, and should influence eyewitness confidence as well. Some are estimator variables, which are beyond the control of the criminal justice system (Wells, 1993). For instance, the amount of time that an eyewitness had the culprit in view during a crime is an estimator variable, although it too may be manipulated in a staged-crime experiment. Some others are physical environment, weapon focus or witness stress, and the problem of inter-racial identification. In short, any factor that affects how well the eyewitness encodes the incident, culprit, and situation is such a variable. People seem to underestimate their effects, and often assume an all-or-nothing approach to memory encoding: whether or not the eyewitness saw a culprit is all important, and how he or she did is not (e.g.. Tomita, 1993). Even if the witness has perceived the crime, culprit, and situation perfectly well, it is still possible for eyewitness memory to be distorted through leading questions as well as misleading information prior to or at the time of recall and recognition (Loftus, 1979). Normally, such factors are estimator variables, just like the time interval between a crime and identification attempts. However, leading questions and misleading information at the time of recall and recognition, for instance, could and should be avoided, making a sort of system variable of such factors. System variables are those that are manipulated in research, and that can also be controlled in actual cases by people in the criminal justice system (Wells, 1993). For a complete understanding of the social and cognitive processes that affect eyewitness testimony, research into both system and estimator variables is necessary. However, since, by definition, system variables are controllable, research on them can help inform the justice system about the ways to reduce eyewitness identification errors (Wells, 1993). System variables may be conceived as those affecting memory retrieval; examples are questions and instructions at the time of identification, and the structure of the lineup or photospread. The number of people in a lineup, or who are distracters in a photospread, could easily influence eyewitness performance, independently of ability. Nevertheless, people often seem to underestimate or ignore their importance; what counts most in the mind of judges and jurors seems to be whether or not 8 Japanese Psychologcat Assoclatlon 1996

3 ~ System variables in eyewitness identification 27 the suspect is identified, regardless of the structure (e.g., Tokuho, 1991). The third purpose of the current research is to study photospread structure in the system-variable approach. Functional size and mock-witness control For this third purpose, our experiments examined the effect of photospread distracter similarity. Seen differently, it is the issue of photospread functional size. To the extent that distracters do not match the culprit description, while the suspect does, the functional size approaches one, unfairly inflating the suspect s chance of identification. If no one, even among those who have not witnessed the crime, chooses anyone but the suspect, with whatever information that is available, the size becomes one. On the other hand, the upper limit of functional size is the nominal size, the actual number of people in the lineup or photospread, which seems to affect neither correct nor false identification rates (Nosworthy & Lindsay, 1990). Functional size is estimated with a control sample of mock witnesses; the photospread is shown to a set of non-witnesses, who are given only limited information about the culprit (Wells, 1993). Theoretically, mock witnesses should spread their guesses with a relatively equal frequency across the alternatives. If they tend to choose the suspect, it is possible that the same limited information alone is used by the actual eyewitness. Given a photospread and culprit description, its functional size regarding a suspect is the reciprocal of the ratio of the suspect identifications to the total attempts. The size becomes smaller as the suspect matches the description better, and the distracters more poorly, making them less similar. Therefore, it can be an index of photospread adequacy; a photospread with a size that is too small cannot be useful or reliable. The experiments and predictions In the current research, an incident was staged during a lecture, and the student witnesses attempted to identify the target 3 months later. Photospread structure as a system variable was examined, with distracters who were similar or dissimilar to the target, giving a large or small functional size. Also, in order to estimate the false identification rate, and evaluate witness performance as well, we had foil control photospreads. Both distracter-similarity and targetpresence factors should affect accuracy of identification. There should be more cases of false identification, and the target should be more easily identified, in the dissimilar condition (Lindsay & Wells, 1980). The relationship between how certain a witness is and how likely he or she is to be accurate is also examined. In addition, with mock-witness controls, frequencies of target as well as foil identification are obtained, with the same photospreads and additional information in the form of target description. The functional sizes computed from the frequencies should reflect distracter similarity. The sizes would then be used in the evaluation of actual witness performance, and of photospreads themselves as well. Incident At around 4:45 p.m. on September 1, with a video camera, the target person entered a large classroom where introductory psychology was taught. Quietly, he went from the back door to the back of the room, and began videotaping the lecturer (the current author). When the lecturer asked the intruder what he was doing, he hesitated and then walked towards him. Speaking few words, he took a name card out of his pocket, and handed it to the lecturer. Asked about permission to videotape, the target nodded and started back to the camera, and as the lecture resumed, he quietly left the room. In all, he was in the room for a little more than 4 minutes, and students attention was on him for 1 minute. A Preliminary Questionnaire Five weeks later, at another lecture, the students of the same class answered a questionnaire2 about the incident and target. Its All the materials and instructions used in the studies were in Jaoanese. 0 Japanese Psychological Association 1996

4 28 K. Kurosawa purpose was twofold: as this was a simulation of an eyewitness experience, it was appropriate for the subjects to become aware of a crime or incident shortly after it and well before any identification attempts, as this changes witness memory, accuracy and confidence; and it was also useful and necessary to find out how confident the students actually were as eyewitnesses. At both lectures, 134 students were present (101 men and 33 women). Results showed that students normally do not pay much attention to an intruder in a classroom, who for them is not particularly novel, exciting or likely to attract their attention. Accordingly, as many as onethird of the class answered that they could not remember the staged incident, although they must have seen it. Some 40% to SO% of the students were not able to say what the person did there. To the crucial question of eyewitness confidence, four were of moderate confidence (coded 3 in subsequent analyses) that they would probably be able to do the task, 13 felt it depended on the material or method of identification (coded 4), 43 thought they were perhaps unable to (S), while 32 had almost no confidence (6), and 42 admitted that they would be completely at a loss (7). Therefore, 17 were somewhat, 43 were less, and 74 (55.2%) were not confident, although more than 60% of them were somehow able to give some information on the target. Although a staged-incident experiment is generally more natural and ecologically valid than a laboratory experiment, there is always some risk that prospective participants fail to pay full attention to or fully perceive the incident. However, such a failure is not at all unexpected, not only in this kind of experiment, but also in our daily life; unless the incident is novel, exciting or otherwise likely to attract attention, we might see it but would not perceive it. Even in such a situation, one may still be called in for eyewitness identification, if one happens to be on the spot. With these issues in mind, we will now turn to the question of how well the students performed in the identification task. Because there were many who claimed that they would not be able to identify the target, it was decided that a verbal description of the target should be provided to help less confident witnesses, while more confident participants could try the identification task as a regular eyewitness would. Experiment 1: Eyewitness identification Method Twelve weeks after the incident, identification experiments began, with participants solicited during a lecture. The potential participants in Experiment 1 were the 60 students who did not choose the alternatives of almost no confidence or completely at a loss to the crucial question in the questionnaire. Photospreads. Eight photospreads were prepared in the following steps. First, 17 persons were selected so that the witnesses were not familiar with them. Two black-and-white pictures (90 mm x 130 mm) were taken of each person, including the target, one with the subject facing directly towards the camera, and the other to the right, showing his right profile, with the person s upper body in front of a wall. The pair were placed side by side on a B5 size page, with the direct-facing picture on the left. Then nine pairs of pictures for each photospread were selected, with the following 2 x 2 factorial design. Pictures of the target were among those for the experimental groups. In the photospreads for foil control, a person (the foil) who was vaguely similar to the target replaced the target. The target and foil were similar in that they both wore thick black hornrimmed glasses, but they otherwise had almost nothing in common. Two groups of distracters, eight each, were used in fixed orders of appearance. In the similar condition, the photospreads had distracters who all wore glasses. One of them wore a pair of glasses that had thin metal frames, another with thin black frames, and the other six with thick black horn-rimmed frames, like those worn by the target and foil. On the other hand, in the dissimilar condition, only one distracter wore glasses, with thin metal frames. The two factors just mentioned, target 0 Japanese Psychological Association 1996

5 System variables in eyewitness identification 29 presence and distracter similarity, formed four experimental groups, for which two photospreads each were used, making eight in all. Procedure. Since two experiments were simultaneously run in the same sessions, appropriate questionnaires were first handed to participants. They were then told that they would be trying to identify the target person of the incident that had taken place 3 months previously. Without opening the photospread that was handed to them, participants were asked two questions about the target. A. How well can you now remember about the person? B. How confident are you that you will be able to spot the person, if you see him? After the questions, participants were reminded of a lecture given earlier on experimental methodology; there should always be experimental and control groups. In this experiment, they were told, the control group photospreads did not contain the target; however, as had been explained then, participants would not be informed of which group they were in. Exactly the same information was given in print. They were also warned that the clothes the target wore in the pictures were different from those he had worn on the day. Absolute and overall judgments. First, participants made absolute judgments. For this task, participants looked at the pages of their booklet one by one, and made a judgment independently of other pictures or judgments they had made. The judgment was How likely is it that the person in the pictures was the person of September l? ; they chose a probability between 0 and 100 (%). After that, participants indicated confidence in their judgment: 1 for absolutely sure to 6 for completely no confidence. After judging nine pairs of pictures, participants made an overall judgment. At this time, they were free to look at all the pictures as much as they wanted, and tried to choose the 31n the two versions. the pictures of the target or foil appeared on the third or seventh of the nine pages Since the cells were not well balanced for a three-way ANOVA including the position factor, the factor was not used target pictures. The alternative Not present in this photospread was given first. Again, they indicated confidence in the judgment in the same way as the absolute judgments. Finally, two additional questions were asked: C. How satisfied are you that you have done well in the experimental tasks today as a whole? D. Finally, do you know any of the nine persons you saw in the photospread? The brief experimental sessions were run with fewer than eight participants at a time (including those for Experiment 2), with their number not specifically controlled. Results Forty-eight students participated, and were randomly assigned to one of the four experimental groups. The degree of confidence indicated in the preliminary questionnaire (coded 1 to 7; the lower, the more confident) and answers to question A or B were not different among the four (p >.15). Comparing of confidence at five weeks with the answer to Question B, which had the same alternatives, 9 indicated more confidence in Question B, and 22 remained the same, while 17 decreased. The change was not statistically significant, in terms of the main and interaction effects of presence, similarity, and contrast (the withinsubject factor of the two repeated measures). The correlation coefficient (df = 46) between the two confidence measures was.405 (p <.Ol), and between the answers to Questions A and B,.691 (p <,001). Overall judgment and confidence measures. The results showed that 13 out of the 24 experimental participants correctly chose the target as the intruder on September 1. However, of the same number of control participants, 10 falsely identified the foil as the target. In the dissimilar condition, 7 of the 12 correctly chose the target, but the same number falsely identified the foil. On the other hand, in the similar condition, six were successful in correct identification under the experimental condition, while only three control participants made a false identification. Although interesting, the correct and false identification pattern, with particularly fewer cases of false identification under the similar 0 Japanese Psychological Association 1996

6 30 K. Kurosawa Table 1. Mean scores on Questions A, B, and overall judgment. confidence for the correct and incorrect groups Group N Question A Question B Overall confidence Correct I 730) 4 50 (816) 3 12 I1 02) Incorrect ( 840) 5 03 ( 897) 3 91 (1 23) Overall ( ( 899) 3 65 (1 21) p = 083 p = 053 p = 034 Note The higher the number, the less memory (A) or confidence (B and Overall) condition, was not statistically significant, ~ (1, N = 48) =.84, p >.35. On the other hand, only 9 out of the 48 participants chose the alternative Not present in this photospread. Of the nine, three were among blank-control participants, and therefore correctly rejected the foil and distracters. However, the other six were among experimental participants, and therefore missed the target. Thus, we now have 16 who made a correct overall judgment (the correct group), and 32 who were wrong (the incorrect group). In terms of how well they remembered the target before the experimental tasks (Question A), the difference between the two groups (correct vs. incorrect) was marginally significant, F(1,46) = 3.14,~ =.083. The confidence in identifying the target (Question B) too was different, F(1,46) = 3.96, p =.053, as was the confidence after the overall judgment, F( 1,46) = 4.79, p =.034. The group means for the three variables are shown in Table 1. On the other hand, they were not at all different in terms of the post-task satisfaction (Question C; p > S). In addition, if only the data for choosers were used, the confidence after the overall judgment was again significantly different, F(1,37) = 5.02, p =.031; the means were 3.15 (SD = 1.14) and 4.00 (SD = l.lo), respectively, but no other variables were. Absolute judgment and confidence measures. For absolute judgments (&loo%), an average was computed for the eight distracter estimates. With the estimate for the target or foil as the other dependent variable, a repeatedmeasure ANOVA was conducted, with the two factors of presence and similarity as the between-subject factor, and contrast (the targetlfoil vs. distracters) as the within-subject repeated factor. No between-subject factors were significant (p >.35), but the main effect of contrast was, F(1,44) = 49.2, p <.001; the means were 43.2 (SD = 28.2) for the targetlfoil estimate, and 16.7 (SD = 11.5) for the distracter average. The interaction effect of contrast by presence too was significant, F(1,44) = 5.06, p <.03, and so was the interaction effect of contrast by similarity, F(1,44) = 6.06, p <.02. However, the three-way interaction effect was not, F (1,44) = 1.38, p >.2. The pattern of the means for the ANOVA model is depicted in the left panel of Figure 1. The same ANOVA was applied to another set of dependent variables: the confidence for the target/foil judgment and the average confidence in the eight distracter judgments. The only significant effect was contrast, the repeated factor, F(1,44) = 9.90, p <.01, meaning that the two indicators of confidence were different from each other. The means were 3.60 (SD = 1.11) for the targetlfoil judgment, and 3.09 (SD = 1.05) for the distracter-judgment average. It is interesting to note that the means indicate that participants were more confident in making judgments when the person was a distracter than he was either the target or foil. Correlation coefficients for the four dependent variables of the two ANOVAs were computed. Confidence for the target/foil judgment and the average confidence of the eight distracter judgments had a significant correlation, r(46) =.453, p <.001, which possibly reflected the individual differences in judgment confidence and/or tendency to openly express it. The average estimate and confidence for eight distracters too had a significant correlation, 0 Japanese Psychological Association 1996

7 System variables in eyewitness identification 31 *O 1 I I I Experiment 3 Experimental Similar: Dissimilar: Control Similar: Dissimilar: target target 0 foil H foil distracters H distracters H distracters distracters Figure 1. Probability estimates in three experiments r(46) =.436, p <.002; the more probable that the participant judged distracters to be the target, the lower was the average confidence. More important, the correlation between the targetlfoil estimate and its associated confidence was not significant, p >.3. The same analysis was repeated for experimental choosers only. The correlation between the two confidence measures was again significant, r(16) =.728, p <.001. The distracter-average estimate-confidence correlation became non-significant, p >.5, but the target estimate now had a significant correlation with both confidence measures: r(16) = -.734, p <.001, for its associated confidence; and r(16) = -.645, p <.004, for the distracter average confidence. The two correlations were not at all significant, 422) <.3, p >.18, if the six nonchoosers were included. For control participants who chose the foil or a distracter, the same two correlations as for all participants were significant. The two confidence measures for the foil and distracter judgments had an r(19) of.478 (p <.03) and the distracteraverage estimate-confidence, an r( 19) of.458 (p <.04) In terms of other correlations, for experimental choosers, the better the participant answered that helshe remembered the target (Question A), the higher the target estimate, 0 Japanese Psychological Associatlon 1996

8 32 K. Kurosawa r(16) = 30, p <.04, and the higher the confidence for the estimate, r(16) =,646, p <,001. However, the pre-task confidence for target identification (Question B) was not related to the levels of estimate or confidence (p >.3). Also, for control choosers, the better the participant answered that he/she remembered the target, the lower was the distracter estimate, r(19) = -.410, p <.065, and the more confident the estimate, r(19) =.753, p <,001. And the higher the participant s pre-task confidence, the more confidence was recorded in the distracter estimate 422) = 568, p <.01. Discussion The results of the experiment were quite revealing. Although many had not been very confident that they would be able to identify the target, more than half of experimental participants correctly chose him. Without knowing the other half of the experiment, namely foilcontrol participants, many of whom falsely identified the foil for the target, we could have arrived at a wrong conclusion. The superb performance of experimental participants was not what it appeared to be, and it is misleading, to say the least, to quote their successful identification rate. They were just lucky that the target was in the photospread; otherwise, many of them too would have made a false identification. Although Figure 1 (left panel) seems to show that the similar-distracter control group was different from the other three experimental groups, the corresponding three-way interaction effect was not significant. Similarly, the xz of target/foil selection frequencies, which tests the same thing, was not significant, corroborating the result further. The pattern should be interpreted as meaning that the dissimilar experimental group had the largest within-subject difference, and the similar control group the smallest, while the other two fell evenly between. And the effects of the two interactions were additive: the distracter similarity effect was independent of the target presence effect. In other words, if distracters were similar to the target or foil, rather than dissimilar, both the choice and perceived probability of the target or foil decreased to the same degree, whichever was included. A significant three-way interaction may have been easier to interpret; nevertheless, the effect of distracter similarity was unmistakable. Our results therefore substantially replicated the findings of Lindsay and Wells (1980). Another important implication was evident in the overall judgment; the participants appeared to have performed the task as if they assumed from the outset that the target was in their photospread, and all they had to do was select the best match in their ecphoric similurity (Wells, 1993). Theirs were relative judgments, which were particularly prone to cause false identification (Wells, 1993). There are several possibilities to explain why they opted for relative judgments. First, the poor memory caused by insufficient attention and long delay in the experiment may have forced them to adopt this strategy. Also, the use of a photospread itself may facilitate the mind set of selecting the best of given alternatives. It was also possible that because the judgment followed absolute judgments in the experiment, participants understood the task to be relative, although the alternative Not present in this photospread was plainly included. Whatever the reason, the relative judgment must be the main cause of the high rate of false identification among control participants. As for the certainty/accuracy issue, the confidence of those who made a correct overall judgment was higher than those who failed in the task (see Table 1). Basically, it was postdecisional confidence that correlated with performance accuracy; however, the memory level and predecision confidence (Questions A and B) too had marginally significant correlations, although they became nonsignificant when nonchoosers were excluded from the analysis. On the other hand, the correlation between the target/foil estimate and its associated confidence in the absolute judgments was not significant, if data from all or experimental participants alone were analyzed. A higher probability that a participant assigned to the target, an index of accuracy, did not seem to mean a higher confidence. 0 Japanese Psychological Associatlon 1996

9 System variables in eyewitness identification 33 However, the correlation surprisingly and strikingly became significant when only data from experimental choosers were used. In addition, for the same group of participants, a higher pretask memory level (Question A) led to a higher estimate and confidence for the target probability, although the pretask confidence for target identification (Question B) did not mean a higher estimate or confidence level. In summary, our experiment generally replicated the findings that postdecision confidence correlated more highly with accuracy than predecision certainty (Perfect et al., 1993; Sporer, 1992, 1993). Also, the correlation was higher if only the data from choosers were used (Sporer, 1992, 1993). Experiment 2: Identification aided with verbal description Method The participants in Experiment 2 were those who had been less confident about identifying the target. In order to help their task performance, a description of the target s appearance and impression was made by a graduate student who saw him on the videotape that had been recorded just prior to the staged incident. Two more students saw the target s pictures in the photospreads and discussed the accuracy of the description. As a result, the face shape, originally square, was changed, and the following description resulted. It was also used similarly in Experiment 3. Description for identification. The hair was not kept very neat. His eyebrows made an arch, with both outsides down. The face as a whole was egg shaped, or perhaps a little longer. He wore black rimmed glasses, had sloping shoulders, and was a bit slight of body. He appeared to be reserved yet conscientious at the same time. Perhaps easily distracted, he did not look a very calm and stable person. Procedure. The questionnaire that participants in Experiment 2 received gave this description at the top. With photospreads still closed, they were asked to make an impression after reading it, and answered the following two questions. A. How well do your memory of the person and the description above match each other? B. With the help of the clues in it, how confident are you that you can correctly identify him? Again, participants were reminded of the blank control condition, and made the absolute and overall judgments in the same way as in Experiment 1. However, the judgments were not about the probability that the pictures were of the target, but how well the pictures matched the description, and which pictures were the best match for the description. Confidence too was asked about as in Experiment 1. In addition, two more questions followed: C. How dependent were you on the description above, when you made your judgments today? D. Finally, do you know any of the nine persons you saw in the photospread? Since Experiments 1 and 2 were run at the same time, the procedure and instructions were identical, except, of course, that the questionnaire had two versions. Results Seventy-seven students participated, including a few who had not seen the incident, but had completed the questionnaire, and were randomly assigned to the four groups. To Question A, concerning how well the description matched the participant s memory, 2 chose very well, 5 fairly well, and 23 more or less, while 17 thought they did not match very well, and 2 were of the opinion that the match was poor. In addition, 28 had no opinion, for they remembered too little of the target. For Question B, regarding pretask confidence in the description-aided identification, 1 participant saw no problem at all, 14 were confident that they would be able to do the task, 12 thought it depended, 24 were not very confident, 19 had almost no confidence, and 7 would be completely at a loss. For the first two questions, the four groups were not different from each other. In addition, participants in Experiment 2 were not different in terms of their pretask confidence from those in Experiment 1,p >.9, although their tasks were somewhat different. 0 Japanese Psychological Association 1996

10 34 K. Kurosawa Table 2. A summary of the three experiments the percentages of target/foil selection and the functional sizes of the photospreads Experimental group Experiment Functional size Experimental Similar 50 0 (12) 61 1 (18) 56 2 (16) 1 78 Dissimilar 583 (12) 81 8 (22) 94 4 (18) 1 06 Control Similar 25 0 (12) 11 l(18) 16 7 (18) (5 991 Dissimilar 58 3 (12) 63 2 (19) 58 8 (17) (1 70) Note. In the parentheses are the numbers of participants Table 2 summarizes the results for the overall judgment in the three experiments, showing the percentage of participants in each experimental group who chose the target or foil as the person who fitted the description best. When Experiments 1 and 2 are compared, it is apparent that the patterns are very similar; again, fewer false identifications occurred when distracters were similar to the foil. The pattern however was not significant, ~~(1, N = 77) = 1.93, p <.2. In this experiment, three participants chose the alternative Not present in this photospread, and all were in the foil control group. Together with the 29 experimental participants who chose the target, we thus have 32 who belonged to the correct group. When compared with the incorrect group, who either missed the target or chose the foil or a distracter, the correct group was more confident of their overall judgment, F(1,75) = 17.2, p <.001; their mean rating was 2.72 (SD = 1.35) as compared with 3.87 (SD = 1.08) of the incorrect group. This difference in confidence may be partially explained by the presence effect on it, F(1,75) = 4.18, p <.05, for most of the correct group were from the experimental group; the experimental group mean was 3.10 (SD = 1.32), and the control group mean 3.70 (SD = 1.27). There was no difference between correct and incorrect groups for Question A or B, or the post-task question of how dependent the participant was on the description in performing the judgmental tasks. Exactly the same procedure as in Experiment 1 was used to analyze absolute judgments and confidence. In the repeated-measure ANOVA, the main effect of presence was significant, F(1,73) = 6.28, p <.02, as was the main effect of contrast, F(1,73) = 76.0,~ <.001; the means were 57.8 (SD = 29.6) for the targetlfoil estimate, and 30.2 (SD = 17.4) for the distracter average. The interaction effect of contrast by presence too was significant, F(1,73) = 18.7, p <.001, and so was the interaction effect of contrast by similarity, F(1,73) = 16.1, p <.001. However, the three-way interaction of the ANOVA model was again not significant, F( 1,73) < 1, p >.8. The means are shown in the center panel of Figure 1. The only effect that was significant in the analysis of confidence was the interaction of contrast by similarity, F(1,73) = 3.96, p =.05. The means indicated that whether distracters were similar to the targetlfoil or not, the confidence for the targetlfoil judgment remained much the same (similar, 3.39, SD = 1.22; and dissimilar, 3.34, SD = l.ll), but the average confidence for distracter judgments was relatively low (3.55, SD =.90) when distracters were similar, and relatively high (3.08, SD = 1.02) when they were not. Experiment 3: A mock-witness control experiment Since Experiment 2 was a mixture, and not really eyewitness identification nor identification with a verbal description, a purer Q Japanese Psychological Association 1996

11 System variables in eyewitness identification 35 control experiment was conducted, with participants who had nothing to do with the initial incident, by giving an identification task with a verbal description. Method About 15 weeks after the incident, participants were solicited in another introductory psychology class for an experiment with the same photospreads. Procedure Participants were first told that the experimenter was studying how well people chose pictures of a real person, given descriptions of the person s appearance, etc. Exactly the same description as in Experiment 2 was used, and it was explained that someone who saw the person made it as accurately as possible. They were asked to carefully read and make an impression of it, and then answer the following questions, with photospreads closed. A. How well can you imagine the person? B. What type of the person is he, given your impression? (This was indicated by a number between 1, very common, and 6, very rare.) C. With the help of clues in the description, how confident are you that you can correctly identify him? Participants in this experiment too were told of the possibility of a blank control group, and made the absolute and overall judgments with confidence indicated, in the exactly same manner as before. In addition, two more questions were asked: D. How satisfied are you that you have done well in the experimental tasks? E. Finally, do you know any of the nine persons you saw in the photospread? Results There were 69 volunteers, and they were randomly assigned to the four groups. To Question A, 1 participant answered that an excellent image was made, 13 replied that a good image was possible, and 39 thought that the task was done fairly well. Only 16 said that they had a hard time imagining the person, but no one said the task was too difficult or impossible. To Question B, 1 participant thought that the person was so common that one would meet him anywhere, 16 answered that he was fairly common, while 26 thought him to be neither common nor rare. There were 23 who judged him to be a rather rare type, and 3 were of the opinion that he was a very rare type; however, none thought he was so rare as to be nonexistent. As for Question C, 6 were so confident with the description that they saw no problem identifying him, 23 thought that they would be able to do the task, and 33 said it depended. On the other hand, 5 were not so sure that they would be able to do it, and 2 had almost no confidence in their performance. In terms of answers to the questions, the four groups were not different from each other. In addition, since the alternatives were the same, whether participants of the three experiments were similar in terms of pretask confidence (Question C) was tested, and participants in Experiment 3 were found to be more confident than the others, F(1,191) = 31.0, p <.001. The means were 4.85 (SD =.899), 4.87 (SD = 1.27), and 3.62 (SD =.859), respectively. Again, the pattern in the numbers of participants who chose the target or foil as fitting the description best is similar; there were fewer false identifications when similar distracters were used. However, as in Experiments 1 and 2, the pattern was not significant, ~ ~(1, N = 69) =.20, p >.65. The functional sizes, shown in the right-most column of Table 2, were the reciprocal of selection ratios in Experiment 3, the mock-witness control experiment. The similar condition had one of 1.78, which was not very high. However, the number was almost 1 for the dissimilar condition, which means that the distracters were not at all distracting. Figure 2 shows the relationship of identification rate to functional size. The curve, the reciprocal of functional size, is the chancelevel baseline, and an identification rate, given a functional size, should be above the curve. Vertical line A, for instance, represents the experimental group with dissimilar distracters in Experiment 3. With a functional size of 1.06, the chance-level identification rate is.944. Point D is the identification rate found in Experiment 1 (.583), which in this context 0 Japanese Psychological Assoclanon 1996

12 36 K. Kurosawa Figure 2. A B C c Functional size Functional size and identification rate. cannot be termed a good performance level at all, because it is far below the chance level. The reason it is far lower than the chance level is that the average eyewitness memory was far poorer than the verbal description used in Experiment 3. Vertical line B stands for the experimental group with similar distracters. In this case, the identification rate, here represented by Point E, was around the chance level. Vertical line C is for the control group with similar distracters, which had a functional size of Although the target was not in it, and therefore the size was not meaningful, the low chance level associated with it tells us that a large functional size is a desirable characteristic. Point F represents the foil false identification rate of experiment 1; it is near the chance-level baseline. There were four who chose the alternative Not present in this photospread, and two of them were among foil control participants. The correct group therefore comprised 28 subjects, including the 26 experimental participants who chose the target. In a comparison of the correct versus the incorrect groups, none of the pretask questions had answers that were different. However, the confidence for the overall judgment was different for the two groups, F(1,67) = 9.45,~ < 005. The means were 2.32 (SD = 1.09) and 3.32 (SD = 1.36), respectively. The difference may be explained by the presence effect on it, which too was significant, F(1,67) = 9.68, p <.005, because almost all correct participants were from the experimental group. The experimental group had a mean of 2.41 (SD = 1.08), and the control group 3.40 (SD = 1.52). No difference was found on the post-task satisfaction (Question D, p > 3. The same pattern of results was found for absolute judgments. The main effect of contrast was significant, F(1,65) = 96.0, p <.001; the means were 60.0 (SD = 28.2) for the target/foil estimate, and 25.4 (SD = 16.6) for the distracter estimate. The contrast by presence interaction effect too was significant, F(1,65) = 6.92, p <.02, and so was the contrast by similarity interaction effect, F(1,65) = 7.26,~ <.01. However, the three-way interaction again was not significant, F(1,65) < 1, p >.3. The means for the ANOVA model are shown in the right panel of Figure 1. The only significant factor in the analysis of confidence for the absolute judgments was contrast, F(1,65) = 6.36,~ <.02. The means indicate that participants were more confident when they made judgments for the distracters (2.36; SD =.759) than for the target or foil (2.65; SD = 1.04). Discussion With regard to the overall and absolute judgments, the results of the last two experiments were so similar that we can discuss them together. Not only were they similar, they also replicated the pattern of the results from Experiment 1. Although participants of Experiment 2 were asked to rate how well the pictures matched the description, they were implicitly made to choose the target. The similarity in the results illuminated the implicit demand of the experiment, and it thus could be considered as a mixture of the other two. Seen this way, the results of the three experiments may be compared meaningfully with each other. From the similarities in the results, we may be justified in concluding that the influence of photospread structure on eyewitness identification performance is clearly demonstrated. 0 Japanese Psychological Association 1996.

13 System variables in eyewitness identification 37 Independent of the effect of presence, the effect of similarity was found in all the experiments. Were we to conduct an identification experiment with only a photospread that had the target among dissimilar distracters, we would completely confound the two effects. The implication for actual eyewitness identification is grave but simple: a suspect could be made to appear to be the culprit if dissimilar distracters were used, which any person with common sense should already know. As for eyewitness certainty, in both experiments, the correct participants (who mostly were in the experimental rather than the control group) were more confident about their task performance. However, there was no difference in terms of pretask confidence between the two groups. Therefore, the higher post-task confidence resulted from a superior performance, which was possible when the target was in the photospread. Again, if we conduct an identification experiment with only photospreads that have the target, and use no control photospreads, the accuracy effect is completely confounded with the presence effect on confidence. For absolute judgments, the general tendency was that the more similar the pictures were judged to be to the target s, the less confident the participant felt. General Discussion From the results of the experiments, we learned that people could identify the target even when they were not very confident that they would be able to. They might feel more certain after the task, for it would be likely for them to feel that they had not performed very poorly, given their surprisingly good results. However, the foil control results showed that false identifications were almost as numerous as correct ones, and that performance was not better than chance. Therefore, the impressive performance of experimental participants was not what it appeared to be, and their certainty was illusory. The results suggest that a control group is essential if we want to evaluate eyewitness accuracy, and false identification rates must be included in any discussion of accuracy. For these purposes, the proposed foil-control method should be especially useful. The results concerning distracter similarity should surprise no one. If distracters were dissimilar to the suspect (or the target in our experiment), an especially high false identification rate was obtained. If they were similar, the rate became quite low, although apparently the similar distracters in our experiments were not very similar. An index of distracter dissimilarity is functional size, and the smaller the size, the more dissimilar the distracters. An objective measure like it should be used to decide whether a photospread is fair. It would be difficult, if not impossible, to judge whether an investigator intentionally compiled a photospread with dissimilar distracters; anyway, such a judgment is beside the point, as Tomita has argued (1993). Instead, a mock-witness control should be used more often and regularly for photospread evaluation. In summary, our experiments from the system-variable approach have shown that the act of witnessing alone does not produce reliable identification results and that photospread structure critically affects outcome. For that reason, comparison of experimental and control groups is crucial, for it is the difference between them, and not performance of the experimental group or actual witness alone, that reflects the act of witnessing. We must have a photospread that maximizes the difference. If a photospread cannot produce a difference that is sufficiently large, it is poor and unreliable, and should not be used for identification. It is also suggested that a figure like Figure 2 be used for evaluation of eyewitness performance. When we have computed the functional size, we want to know whether the experimental-group identification rate is any better than chance. The target and foil identification rates can be plotted in the figure, represented by points on lines corresponding to appropriate functional sizes. Such graphical representation should help in such evaluations. Our data would not allow us to discuss the comparison of between- versus within-subject 0 Japanese Psychological Association 1996

14 38 K. Kurosawa correlations (cf., Perfect et al., 1993), or that of accurate versus inaccurate choosers (cf., Wells & Lindsay, 1985), because we had only one target, and there were too few nonchoosers or inaccurate choosers. However, we learned that postdecision confidence in general was related to performance accuracy, as already reported (Perfect et al., 1993; Sporer, 1992, 1993). In some cases, data from choosers showed strong correlations between confidence and accuracy, which supported previous claims (Sporer, 1992, 1993). As already noted, however, the confidenceaccuracy correlation could be illusory, for an unexpectedly easy task should boost both accuracy and postdecision confidence. In the process, both the similarity effect on accuracy and the presence effect on confidence contribute to the correlation. For these reasons, the accuracy-confidence relation should be examined in the context of experimental and control groups. Also, predecision confidence is free of the similarity and presence confounds, but we found that the correlation associated with it was consistently low or nonexistent. As for choosers versus nonchoosers, we have to realize that the meaning of confidence could be ambiguous, for someone may not choose a person in a lineup or photospread if helshe has no confidence, or is completely sure that the target is not there. Because this ambiguity is eliminated, the accuracy-confidence relation may be stronger among choosers. Finally, an area in eyewitness research needs to be studied more, namely naive psychology. We do not know enough about the beliefs people have about eyewitnesses, and rely mostly on anecdotal knowledge for our discussion. What people believe about the ability or other characteristics of an eyewitness is important, because it could affect eyewitness performance itself. An eyewitness after all is not very likely to be a psychologist. Also, judges and jurors tend to judge an eyewitness and hislher testimony in the general public's framework. Psychologists should study more about naive psychology, in order to better understand eyewitness performance, and also to become better able to educate the general public about shortcomings, problems, and failures in performance. References Lindsay, R. C., & Wells, G. L. (1980). What price justice? Exploring the relationship of lineup fairness to identification accuracy. Law and Human Behavior, 4, Loftus, E. F. (1979). Eyewitness testimony. Cambridge, MA: Harvard University Press. Loftus, E. F. (1993). Psychologists in the eyewitness world. American Psychologist, 48, Nosworthy, G. J.,,& Lindsay, R. C. (1990). Does nominal lineup size matter? Journal of Applied Psychology, 75, Perfect, T. J., Watson, E. L., & Wagstaff, G. F. (1993). Accuracy of confidence ratings associated with general knowledge and eyewitness memory. Journal of Applied Psychology, 78, Smith, V. L., Kassin, S. M., & Ellsworth, F'. C. (1989). Eyewitness accuracy and confidence: Withinversus between-subjects correlations. Journal of Applied Psychology, 74, Sporer, S. L. (1992). Post-dicting eyewitness accuracy: Confidence, decision-times and person descriptions of choosers and non-choosers. European Journal of Social Psychology, 22, Sporer, S. L. (1993). Eyewitness identification accuracy, confidence, and decision times in simultaneous and sequential lineups. Journal of Applied Psychology, 78, Tokuho: Jiminto honbu houka jiken daiisshin hanketsu. (1991). Hanrei Times, 763, (October 1, 1991) (in Japanese). Tomita, T. (1993). Experiment on memory versus eyewitness identification. Gakujutu Kenkyu, School of Education, Waseda University, Series of Educational Psychology, 41,55-71 (in Japanese). Wells, G. L. (1993). What do we know about eyewitness identification? American Psychologist, 48, Wells, G. L., & Lindsay, R. C. (1985). Methodological notes on the accuracy-confidence relation in eyewitness identification. Journal of Applied Psychology, 670, Wells, G. L., Ferguson, T. J., & Lindsay, R. C. (1981). The tractability of eyewitness confidence and its implications for triers of fact. Journal of Applied Psychology, 66, (Received April 20,1995; accepted Sept. 9, 1995) 0 Japanese Psychological Association 1996