Browsing by Author "Tredoux, Colin G"

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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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    The Dangers of Speaking a Second Language: An Investigation of Lie Bias and Cognitive Load
    (2020) Dippenaar, Andre; Tredoux, Colin G
    Today's world is an interconnected global village. Communication and business transactions are increasingly conducted in non-native languages. Literature suggests that biases are present when communicating in non-native languages; that a truth bias is present in first language communication, and a lie bias in second language communication. Less than 10% of South Africa's population identifies with English, the lingua franca of the country, as a first language. Not much research in the presence of bias in second language communication has been published in the South African multi-lingual context. This study evaluated the presences of bias within deception frameworks such as the Truth Default State and the veracity effect. This study investigated whether deception detection can be improved by modifying the conditions under which statements are given by placing statement providers under cognitive load. The accuracy of veracity judgment language profiling software, LIWC2015, using published deception language profiles was compared against the results of the participating veracity judges. Results of the study were mixed. It was consistent with extant literature in a presence of a truth bias overall, but mixed in terms of a lie bias. The results supported the Truth Default Theory and veracity effect frameworks. LIWC2015 performed marginally better than human judges in evaluating veracity.
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    The own-group bias in face processing: the effect of training on recognition performance
    (2020) Wittwer, Tania; Tredoux, Colin G; Py, Jacques
    The own-group bias in face recognition (OGB) is the greater facility to distinguish and recognize people from one's own group at the expense of people from other-groups. The OGB has been studied for many years, however, very little research focuses on finding a way to decrease or eliminate it, through training. Reporting five studies involving memory or matching tasks, the aim of the present thesis was to develop and to explore to what extent training can decrease or remove the OGB. French White participants, and South African White, Black and Coloured participants took part in different studies, using Black and White faces as stimuli. In each study, White participants from both countries presented the expected OGB prior to any intervention. However, the presence of the OGB in South African Black participants was detected only in one (matching task) study, instead recording a higher discrimination performance by Black participants for White faces in the other studies. As expected, South African Coloured participants did not display increased discrimination performance for any of the other stimuli groups, both being out-group stimuli. Results from the training studies revealed either (a) no effect of a distributed training in feature focus over 5 weeks; (b) an increase of the OGB after a focus on critical facial features; (c) a decrease of the OGB in a task-specific training using pictures whose quality had been manipulated, and; (d) an important implication of the presence/absence of the target in a field detection study. With some promising results, the present work contributes to our understanding of how training could be used to improve face-recognition, and especially other-group face recognition.
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    Utilisation and usefulness of face composites in the South African Police Service - an evaluation study
    (2006) Schmidt, Heike C; Tredoux, Colin G
    The current study investigates the degree to which face composites are utilised as an investigative tool in the South African Police Service. The article provides an overview of the conditions under which composites are produced by eyewitnesses to a crime, and points out constraints in terms of their usefulness and applicability. Composites were found to be produced after a longer delay than is recommended, and predominantly in violent and menacing crimes. Conviction rates for composite-related crimes were very low. However, more insight into actual use and case characteristics is needed before concluding on the usefulness of composites as an investigative tool or evidence. Directions for further research in this area are explored.