Amina Memon (1996) A Consideration of Individual Differences and. Psycoloquy: 7(24) Witness Memory (10)

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PSYCOLOQUY (ISSN 1055-0143) is sponsored by the American Psychological Association (APA).
Psycoloquy 7(24): A Consideration of Individual Differences and

Reply to Douglas on Witness-Memory

Amina Memon
School of Human Development
University of Texas at Dallas
Box 830688 (GR 4.1)
Richardson, TX 75083-0688

Sarah V Stevenage
Department of Psychology
University of Southampton
Highfield, Southampton SO17 1BJ


Douglas (1996) suggests that the individual characteristics of participants, particularly their imagery ability, should be considered. We agree with Douglas's concerns and highlight some of the practical benefits and limitations of adopting an individualistic approach.


Cognitive interview, errors, eyewitness memory, facilitated recall, police procedures, questioning, recovered memories, structured interview.
1. Douglas (1996) suggests that we look at the development of children's memory abilities and provide a theoretical explanation for the younger child's inability to effectively use some of the cognitive interview (CI) techniques. The developmental literature on this is vast and we refer interested readers to the individual papers for a detailed discussion of the issues (see Memon et al., 1993; see Weinert & Perlmutter, 1988, for a review). The general finding is that, with maturation, there is a transition from a relatively passive mode to a more active technique of memorisation. Furthermore, training studies have shown that there is a link between strategy, use, and recall; by instructing younger children to rehearse more actively, their recall can be improved (see Ornstein & Naus, 1978). It was on the basis of this literature that we attempted to "train" younger children in the use of CI techniques.

2. There are several reasons why the children had difficulty with the use of CI mnemonics in the Memon et al. (1993) and Memon et al. (1996) studies, but it is difficult to tease these apart. However, one possibility is that the children lacked metamemory information. We know there are developmental changes in a child's understanding of how memory works and in their grasp of the demands of various memory tasks (Wellman, 1983). Indeed metamemory probably plays a large part in the development of mnemonic skills and yet has been relatively unexplored. We therefore concur with Douglas that theoretical explanations for age differences in the use of CI techniques should be the subject of further investigation and that this should be placed within the context of the developmental literature on memory. We also agree that a child's knowledge-base and ease of access to stored information will influence memory performance as illustrated by Fuzzy trace theory (see also Milne, 1996). We have taken this into consideration in our analysis of schema related errors in the CI (Wark et al., 1995).

3. The situation regarding individual differences in children's ability is rather more confusing than it appears. In our CI studies with children, we did in fact look at the influence of age, gender, and verbal ability. However, because we did not find any clear differences, these effects are not detailed in the published manuscripts. This is not to say these factors are unimportant. A qualitative analysis of our transcripts show that some children are more sophisticated than others in their verbal descriptions, and Memon et al. (in press-a) noted large variations in children's linguistic styles and communication ability. Given the importance of styles of language in the courtroom, and, in particular, the reduced credibility attached to testimonies of poor linguistic sophistication, these individual differences clearly warrant further investigation (see also Schwartz-Kenney, Bottoms & Goodman, 1996).

4. In her commentary, Douglas suggests that a number of personality measures can be used to study individual differences in memory performance. As an example she cites some recent work conducted by Hyman and Billings (1995). This is an excellent example of where the "individual difference" approach may prove to be very fruitful as it may identify characteristics of persons who are most likely to be vulnerable to suggestion. This work is in its infancy, however, and in some cases it is not entirely clear what these personality tests are really measuring or what the correlates are (see below).

5. Douglas places considerable emphasis on links between imagery ability and memory performance and in doing so has raised an extremely contentious issue. First of all it is very difficult to tap into imagery ability: rather than being an undifferentiated general skill, the ability to use imagery may actually draw upon a range of sub-abilities (Kosslyn et al., 1984). The situation is further compounded by the fact that self report measures of imagery do not always correlate well with either standardised imagery tests or behavioural indices (Kaufmann, 1983; Marschark, 1988; White et al., 1977). For these reasons, our knowledge of the individual differences in imagery ability is limited. For example, we know that there are differences in the fluency and the vividness of mental images (Katz, 1983) but we do not know much about differences in the precision or the use of imagery across individuals.

6. The purported link between source monitoring and imagery is however, an interesting one and Dobson and Markham provide us with some relevant data. Dobson and Markham (1993) were interested in the effect of self reported vividness of visual imagery on the ability of eyewitnesses to discriminate between memories derived from two external sources. Participants were classified as "high" or "low" imagers on the basis of Mark's (1973) scale of vividness of visual imagery (VVIQ). All participants then watched a film of a crime. They were later given a written account of the crime that included information not seen in the film. At a subsequent test the high imagers were poorer than the low imagers at discriminating the source of items from the written description. This fits with Douglas's hypothesis that high imagers are more likely to make source confusion errors. Unfortunately we were unable to replicate Dobson and Markham's findings in our laboratory (Johnson & Memon, 1995 unpublished undergraduate project, University of Southampton). As indicated in the target paper, however, the link between imagery and source confusion errors is worth pursuing. Douglas noted that there is increasing evidence from research conducted by Ceci and colleagues suggesting that imagery can lead to confabulated recall. We would however urge readers to read the individual papers published from this laboratory (e.g., Leichtman & Ceci, 1995; Ceci et al., 1994) so that they can be clear about the conditions under which errors and intrusions occur.

7. With respect to eyewitness suggestibility, we wish to reiterate and expand upon the point made earlier about adopting an individual difference approach. In a recent study of the CI conducted in our laboratory (Memon et al., in press-b) we examined individual differences in vulnerability to suggestion and found that we could easily classify children into "high" and "low" vulnerability groups based on their responses to pre-interview suggestions. A more systematic way of measuring suggestibility would be to use something like the Gudjonsson Suggestibility Scale (GSS). This has been used with adults and more recently, children to assess responses to misleading questions and reactions to negative feedback in eyewitness simulation studies and forensic contexts (see Gudjonsson, 1987; 1992; Gudjonsson & Clare, in press for description of the GSS and review). The GSS is an interesting measure because it tries to tap into the witness's expectations about (a) how they will perform in an interview and (b) the general coping strategies that they enter an interview with (e.g., willingness to accept the interviewer's hypotheses). Gudjonsson et al.'s work appears particularly useful in examining the individual differences amongst interviewees, however, it could be developed further to take account of the specific experimental conditions that we know affect suggestibility (see Schooler & Loftus, 1986).

8. The question remains as to how we can reduce suggestibility effects and errors in the CI. Douglas suggests that we avoid use of the mental imagery component of the CI. However, as we argue in our target paper, it is in the question phase of the CI (where imagery instructions are employed) that we get the most significant gains in information (Memon et al., in press-a). This comes back to what has now become an old chestnut: do we sacrifice the gains in correct details in order to reduce errors or do we try to maximise the amount of correct information that can be recalled? Rather than reiterate our thoughts here, we refer interested readers back to the target article where this issue is discussed fully. However, it may be useful here to consider the strategies that have been implemented to reduce suggestibility in the CI. In the child witness area some innovative techniques have been used by Saywitz and colleagues (Saywitz & Snyder, 1993). For example, children listen to a story about a child who went along with the suggestions of an adult interviewer and the unanticipated negative consequences are spelled out and discussed. Children are then trained in appropriate response strategies. With adult witnesses, a warning has been found to induce resistance to misleading information (Greene et al., 1982). Interviewer behaviour has also been found to influence responses to misleading questions: children interviewed by a warm supportive interviewer may be more resistant to misleading questions about the event than children interviewed in an intimidating manner (Carter et al., 1996). This again highlights the importance of the social elements of the CI and the value of conducting a good quality interview.

9. Douglas has raised some important theoretical issues and concerns about the suggestibility of child witnesses and we have elaborated upon some of the points she has raised. We agree that an individual difference approach is called for. As indicated by Schooler and Loftus (1986) "Experimentalists often appear to forget that the performance of the average subject is a convenient summary statement but may reflect the performance of few. The individual difference approach appreciates that people come into a situation with varying backgrounds and abilities." (p.111)


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