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I urval från Stockholms universitets publikationsdatabas

• Retrieval effort and accuracy in eyewitness testimony

  2023. Philip U. Gustafsson.

  Avhandling (Dok)

  For better or worse, eyewitness testimonies make up common evidence in criminal trials. This has the benefit that it allows for guilty offenders to be convicted even in the absence of physical evidence. However, the fallibility of memory also means that eyewitnesses may be mistaken in their recall, risking wrongful, innocent convictions. This dilemma has sparked a multitude of studies on situations and factors that distort memory and make it unreliable, and consequently, situations where a testimony should be reliable. It has also sparked research into methods that attempt to distinguish between correct and incorrect memories. It is this latter research that forms the foundation for this thesis.

  In this thesis, I have attempted to improve judgments of eyewitness accuracy by examining the relationship between expressions of effort in memory retrieval, and accuracy. The thesis builds upon earlier studies demonstrating a negative relationship between retrieval effort and accuracy (easily retrieved memories are more often correct), and explores this relationship further in eyewitness testimonies, while also addressing a number of limitations. Three empirical studies were undertaken, wherein participants saw a fictitious crime and were interviewed as eyewitnesses (Study I & II), or read testimonies and judged the accuracy of statements (Study III). Study I showed that four (para)verbal markers of retrieval effort (“retrieval-effort cues”) were more common in incorrect recall compared to correct recall in eyewitness testimonies. Study I also showed that the retrieval-effort cues mediated between confidence in a memory, and accuracy. Study II replicated Study I and moreover, showed a robustness of the findings, as retrieval-effort cues predicted accuracy both directly after viewing an event, as well as two weeks later, even when witnesses had actively engaged in memory repetition. Finally, Study III showed that fact finders could be instructed to use retrieval-effort cues to predict memory accuracy, and furthermore, results suggested that this method could be superior to fact finders’ spontaneous accuracy judgments. Taken together, this thesis provides evidence that brings us closer to a working method to judge eyewitness accuracy, and illuminates important next steps to be solved, moving forward.

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• Vocal characteristics of accuracy in eyewitness testimony

  2023. Philip U. Gustafsson, Petri Laukka, Torun Lindholm. Speech Communication 146, 82-92

  Artikel

  In two studies, we examined if correct and incorrect testimony statements were produced with vocally distinct characteristics. Participants watched a staged crime film and were interviewed as eyewitnesses. Witness responses were recorded and then analysed along 16 vocal dimensions. Results from Study 1 showed six vocal characteristics of accuracy, which included dimensions of frequency, energy, spectral balance and temporality. Study 2 attempted to replicate Study 1, and also examined effects of emotion on the vocal characteristic-accuracy relationship. Although the results from Study 1 were not directly replicated in Study 2, a mega-analysis of the two datasets showed four distinct vocal characteristics of accuracy; correct responses were uttered with a higher pitch (F0 [M]), greater energy in the first formant region (F1 [amp]), higher speech rate (VoicedSegPerSec) and shorter pauses (UnvoicedSegM). Taken together, this study advances previous knowledge by showing that accuracy is not only indicated by what we say, but also by how we say it.

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• Eyewitness accuracy and retrieval effort: Effects of time and repetition

  2022. Philip U. Gustafsson, Torun Lindholm, Fredrik U. Jönsson. PLOS ONE 17 (9)

  Artikel

  An important task for the law enforcement is to assess the accuracy of eyewitness testimonies. Recent research show that indicators of effortful memory retrieval, such as pausing and hedging (e.g. “I think”, “maybe”), are more common in incorrect recall. However, a limitation in these studies is that participants are interviewed shortly after witnessing an event, as opposed to after greater retention intervals. We set out to mitigate this shortcoming by investigating the retrieval effort-accuracy relationship over time. In this study, participants watched a staged crime and were interviewed directly afterwards, and two weeks later. Half the participants also carried out a repetition task during the two-week retention interval. Results showed that the retrieval-effort cues Delays and Hedges predicted accuracy at both sessions, including after repetition. We also measured confidence, and found that confidence also predicted accuracy over time, although repetition led to increased confidence for incorrect memories. Moreover, retrieval-effort cues partially mediated between accuracy and confidence. 

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• Judging the accuracy of eyewitness testimonies using retrieval effort cues

  2021. Philip U. Gustafsson, Torun Lindholm, Fredrik U. Jönsson. Applied Cognitive Psychology 35 (5), 1224-1235

  Artikel

  Recent research has shown that incorrect statements in eyewitness testimonies contain more cues to effortful memory retrieval than correct statements. In two experiments, we attempted to improve judgments of testimony accuracy by informing participants about these effort cues. Participants read eyewitness testimony transcripts and judged statement accuracy. Performance was above chance in both experiments, but there was only a significant effect of the effort-cue instruction in Experiment 2. In Experiment 1, we also compared judgment accuracy between police detectives, police students and laypersons, and found no significant difference, in contrast to previous studies. Moreover, the current study corroborates previous findings that (a) judging testimony accuracy is a difficult task and (b) people spontaneously rely on effort cues to some extent when judging accuracy. However, a complete reliance on effort cues showed substantially better performance than relying on one's own judgments skills at best, and offered equal performance at worst.

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• 'He was...uhm...bald'

  2019. Philip Gustafsson, Torun Lindholm, Fredrik Jönsson. Book of Abstracts, 327-327

  Konferens

  Evaluating eyewitness testimonies has proven a difficult task. We investigated if incorrect memories are more effortful to retrieve than correct memories. Participants watched a simulated crime and were interviewed as eyewitnesses. We then analysed retrieval effort cues in witness responses. Results showed that incorrect memories included more “effort cues” than correct memories, and also partially mediated the relationship between confidence and accuracy.

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• Effort in Memory Retrieval Predicts Accuracy in Eyewitness Testimonies

  2019. Philip Gustafsson, Torun Lindholm, Fredrik U. Jönsson.

  Konferens

  Do sincere eyewitness testimonies contain objective markers of accuracy? We show that expressions of effort in memory retrieval predict eyewitness accuracy. Incorrect memories are recalled with greater effort than correct memories.

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• Effort in Memory Retrieval Predicts Accuracy in Eyewitness Testimonies

  2019. Philip Gustafsson, Torun Lindholm, Fredrik Jönsson.

  Konferens

  Do sincere eyewitness testimonies contain objective markers of accuracy? Despite the importance of evaluating the accuracy of verbal eyewitness testimonies, the evidence for objective measures are scarce, and current accuracy measures unsatisfactory. We demonstrate that expressed effort during memory retrieval can predict accuracy in honest eyewitnesses. Incorrect memories are recalled with greater effort (e.g. more delays and disfluencies) than correct memories.

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• Predicting Accuracy in Eyewitness Testimonies With Memory Retrieval Effort and Confidence

  2019. Philip U. Gustafsson, Torun Lindholm, Fredrik U. Jönsson. Frontiers in Psychology 10

  Artikel

  Evaluating eyewitness testimonies has proven a difficult task. Recent research, however, suggests that incorrect memories are more effortful to retrieve than correct memories, and confidence in a memory is based on retrieval effort. We aimed to replicate and extend these findings, adding retrieval latency as a predictor of memory accuracy. Participants watched a film sequence with a staged crime and were interviewed about its content. We then analyzed retrieval effort cues in witness responses. Results showed that incorrect memories included more “effort cues” than correct memories. While correct responses were produced faster than incorrect responses, delays in responses proved a better predictor of accuracy than response latency. Furthermore, participants were more confident in correct than incorrect responses, and the effort cues partially mediated this confidence-accuracy relation. In sum, the results support previous findings of a relationship between memory accuracy and objectively verifiable cues to retrieval effort.

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