Browsing by Author "Nortje, Alicia"

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    A systematic review and meta-analysis examining the effect of stress at encoding on line-up performance
    (2022) Gering, Milton Anthony; Tredoux, Colin G; Nortje, Alicia
    Although much research has been conducted on the effect of stress on eyewitness memory, the answer to this question remains unclear. Whereas a previous meta-analysis (Deffenbacher et al., 2004) concluded that stress negatively affects eyewitness identification ability, recent studies have shown a lack of consensus. As most crimes are stressful events and eyewitness evidence is influential in courts; clarity on the effect of stress is important to legal systems around the world. It is difficult to summarise extant research as many studies use differing methods making the source of disagreement unclear. Added to that, many studies report insufficient detail needed to judge the rigour of research designs, and thus the effects of stress. The present systematic review attempts to synthesise the literature and presents an analysis using recent meta-analytic techniques that allow for the influence of moderator variables to be quantified. It shows that the effect of stress at encoding on line-up decisions is not clear, with studies reporting both positive and negative effects, and examines reasons for differences in effects found between studies. A finding of note is that sequential or simultaneous line-up presentation has a moderating effect of stress on line-up performance. Additionally, a multilevel model shows that using continuous, rather than dichotomous, measures of stress may clarify the stress-performance relationship. Recommendations for further research are made in the hope that new studies can answer the important question of whether witnesses who experience high levels of stress at encoding are likely to make better or worse line-up decisions.
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    Contribution of Role Recollection and Perpetrator Identification to the Accuracy of Multi-perpetrator Eyewitness Testimonies
    (2021) Allen, Caroline; Tredoux, Colin; Nortje, Alicia
    Eyewitness testimonies serve as heavily weighted evidence in criminal investigations. Despite this, research has demonstrated the fallibility of eyewitness memory, especially for crimes involving more than one perpetrator. The task for multi-perpetrator eyewitnesses is unique as they not only have to identify perpetrators, but describe the roles played in the crime and then assign an action to each perpetrator. This study examined factors affecting perpetrator identification, role recollection, and perpetrator-role pairing. Participants (N = 216) watched a staged video of a crime and then completed online tasks based on what they saw. At encoding, participants viewed one, two, or five perpetrators. Participants were either required to identify perpetrators from line-ups or were given images of each offender. In addition, they were either required to describe each perpetrator's role or were given this information. For methodological reasons, no perpetrator-absent line-ups were included in the current research as participants who viewed this kind of line-up had no potential for scoring along the perpetrator-role pairing measure. The results suggest that, as the number of perpetrators increases, participants made fewer correct identifications, role recollections, and pairings. However, there was no significant difference in identification accuracy between the one-and two-perpetrator conditions. The findings also show that while receiving experimenter-defined roles yields more accurate pairings, receiving photographs of the perpetrators does not. Future research is needed into the pairing process, the findings of which could be used to improve police procedure for interviewing multiperpetrator eyewitnesses.
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    Face off : automatic versus controlled processing: does a shift in processing affect facial recognition?
    (2011) Nortje, Alicia; Tredoux, Colin
    Working from the transfer-inappropriate processing shift (Schooler, 2002), this project aimed to investigate whether a shift from automatic to controlled processing would impair face recognition rates, much like the manipulated Navon letters do (Perfect, Weston, Dennis, & Snell, 2008), thus providing an alternative explanation for the mechanism underlying the verbal overshadowing effect (Schooler & Engstler-Schooler, 1990).
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    The butcher, the baker, the candlestick maker: investigating facial recognition for multiple-perpetrator crimes
    (2018) Nortje, Alicia; Tredoux, Colin; Vredeveldt, Annelies
    In the United States, 20% of all violent crime is committed by multiple perpetrators. Despite the prevalence of multiple-perpetrator crimes, most published eyewitness research uses a single-perpetrator paradigm: that is, witnesses view a crime committed by a single perpetrator whom they must recognise later. Multiple-perpetrator crimes, however, present with several problems. Police procedure for administering multiple-suspect parades is poorly defined. Furthermore, eyewitnesses must make multiple identifications, and are tasked with a unique memory problem of perpetrator-role assignment. I studied these problems in the following ways: (a) a survey among South African detectives (N = 75) to investigate how multiple suspect parades are administered in practice; (b) two face recognition experiments where the number of face-attribute pairs was manipulated at encoding to investigate the effect of set size on both item recognition (for attributes and faces), and associative memory performance (i.e., matching identity to role; N = 70, and N = 67); (c) an eyewitness experiment where participants studied a simulated crime committed by up to 10 perpetrators whom they had to recognise later (N = 200); and (d) a set of simulations testing a revised version of the Interactive Activation and Competition network proposed by Burton et al. (1990) as a computational account of the memory difficulties experienced by eyewitnesses to multiple-perpetrator crimes. Overall, the results suggest that associative memory is particularly vulnerable to the negative effects of set size, and that role-players in law and psychology should consider the implications of these difficulties in court and the laboratory.