Applying Signal Detection Models to Investigate the Effect of Sequential Item Presentation on the Police Lineup Task

Much research investigating the police lineup has argued that presenting items sequentially is superior to presenting them simultaneously, because sequential presentation reduces rates of innocent suspect identification, minimising the chance of false conviction. However, the research program that arrived at this conclusion was resolutely applied in focus, directing less attention to developing theories that might explain how sequential item presentation achieves this outcome. Recent research has addressed this issue by applying signal detection theory to understanding the lineup task. This mathematical modelling framework characterises observed performance on a recognition memory test, such as the police lineup, as resulting from two latent variables; discriminability, the ability to distinguish target items (guilty suspects) from non-target items, and response bias, conceptualised as willingness to choose. Research employing this framework suggests that sequential item presentation achieve its reduction in innocent suspect identifications by encouraging witnesses to choose less readily than simultaneous presentation, rather than by increasing discriminability. Some studies also find that discriminability is greater for simultaneous presentation and that, on this basis, it should be preferred. However, this body of recent research has employed analysis techniques that fail to capture the unique constraints of sequentially presented lineup tasks. This may compromise the measurement of discriminability (and response bias), leading to incorrect conclusions when comparing sequentially presented lineup tasks to the simultaneous lineup. This thesis addresses this limitation by developing signal detection models that capture the structural constraints of sequentially presented lineup tasks. These models are used in studies one and two to compare simultaneous lineup presentation to two sequentially presented lineup tasks, one on which identification of the current item terminates the task (stopping rule) and another on which two full laps of the items is completed before an identification decision is made, as used in the United Kingdom (UK). Study three develops a model for examining changes in discriminability and response bias by serial position in the sequential stopping rule lineup. Each study involved the collection of new experimental data and studies one and three also analysed previously published datasets. The results of studies one and two imply that sequential item presentation may have a small negative effect on discriminability compared to simultaneous presentation, but this effect was not consistently observed. Effects on response bias were larger and more reliable; the sequential stopping rule lineup was associated with the most conservative overall choosing, followed by the simultaneous lineup, then the UK sequential lineup. In study three, discriminability increased from serial position one to position two in the sequential stopping rule lineup, but not beyond. Changes in response bias by serial position differed depending on whether an identification was made before or after the presentation of the guilty suspect. Taken together, these results imply that there is no compelling reason for policymakers to prefer sequentially presented lineups to the simultaneous lineup. The insights generated from this thesis demonstrate the value of a formal modelling and approach and the need to consider carefully the match between model, task, and research question.Thesis (Ph.D.) -- University of Adelaide, School of Psychology, 202

Do sequential lineups impair underlying discriminability?

© 2020, The Author(s). Debate regarding the best way to test and measure eyewitness memory has dominated the eyewitness literature for more than 30 years. We argue that resolution of this debate requires the development and application of appropriate measurement models. In this study we developed models of simultaneous and sequential lineup presentations and used these to compare these procedures in terms of underlying discriminability and response bias, thereby testing a key prediction of diagnostic feature detection theory, that underlying discriminability should be greater for simultaneous than for stopping-rule sequential lineups. We fit the models to the corpus of studies originally described by Palmer and Brewer (2012, Law and Human Behavior, 36(3), 247–255), to data from a new experiment and to eight recent studies comparing simultaneous and sequential lineups. We found that although responses tended to be more conservative for sequential lineups there was little or no difference in underlying discriminability between the two procedures. We discuss the implications of these results for the diagnostic feature detection theory and other kinds of sequential lineups used in current jurisdictions

A Model of Position Effects in the Sequential Lineup

What is the effect of placing the suspect in different positions in a sequential lineup? To explore this question, we developed and applied a model called the Independent Sequential Lineup model which analyzes a sequential lineup in terms of both identification position, the position at which the witness identifies a lineup item as the target, and target position, the position at which the target or suspect appears. We conducted a large-scale online eyewitness memory experiment with 7,204 participants each of whom was tested on a 6-item sequential lineup with an explicit stopping rule. The model fit these data well and revealed systematic effects of lineup position on underlying discriminability and response criteria. We also fit the model to data from a similar pair of experiments conducted recently by Wilson, Donnelly, Christenfeld and Wixted (2019; Journal of Memory and Language, 104, 108-125) both with and without application of a stopping rule. In all data sets, if a stopping rule is applied, underlying discriminability was found to be constant, or to increase slightly, across target position. In the absence of a stopping rule, discriminability was found to decrease substantially. We also observed a substantial increase in response criteria following presentation of the target. We discuss the implications of these findings for current theories of recognition memory and current applications of the sequential lineup in different jurisdictions

R Code for Eyewitness Data

This is a repository for code presented at the SARMAC regional meeting 201

A model of position effects in the sequential lineup

What is the effect of placing the suspect in different positions in a sequential lineup? To explore this question, we developed and applied a model called the Independent Sequential Lineup model which analyzes a sequential lineup in terms of both identification position, the position at which the witness identifies a lineup item as the target, and target position, the position at which the target or suspect appears. We conducted a large-scale online eyewitness memory experiment with 7,204 participants each of whom was tested on a 6-item sequential lineup with an explicit stopping rule. The model fit these data well and revealed systematic effects of lineup position on underlying discriminability and response criteria. We also fit the model to data from a similar pair of experiments conducted recently by Wilson, Donnelly, Christenfeld and Wixted (2019; Journal of Memory and Language, 104, 108–125) both with and without application of a stopping rule. In all data sets, if a stopping rule is applied, underlying discriminability was found to be constant, or to increase slightly, across target position. In the absence of a stopping rule, discriminability was found to decrease substantially. We also observed a substantial increase in response criteria following presentation of the target. We discuss the implications of these findings for current theories of recognition memory and current applications of the sequential lineup in different jurisdictions

Do Sequential Lineups Impair Discriminability?

The debate regarding the best way to test and measure eyewitness memory has dominated the eyewitness literature for more than thirty years. We argue that to resolve this debate requires the development and application of appropriate measurement models. In this study we develop models of simultaneous and sequential lineup presentations and use these to compare the procedures in terms of discriminability and response bias. We tested a key prediction of the diagnostic feature detection hypothesis that discriminability should be greater for simultaneous than sequential lineups. We fit the models to the corpus of studies originally described by Palmer and Brewer (2012, Law and Human Behavior, 36(3), 247-255) and to data from a new experiment. The results of both investigations showed that discriminability did not differ between the two procedures, while responses were more conservative for sequential presentation compared to simultaneous presentation. We conclude that the two procedures do not differ in the efficiency with which they allow eyewitness memory to be expressed. We discuss the implications of this for the diagnostic feature detection hypothesis and other sequential lineup procedures used in current jurisdictions

Taurine: energy drink for T cells

The activation of T cells causes many cellular changes, including alterations in cell morphology, motility, and size. While all immunologists know that T cells increase their size and become "blasted" upon activation, little attention has been paid to the question of how cell size is regulated and how this process influences T-cell responses. In this issue of the European Journal of Immunology, Kaesler et al. [Eur. J. Immunol. 2012. 42: 831-841] demonstrate that the organic osmolyte taurine and its transporter Taut are instrumental in driving cell-volume regulation and therefore the T-cell response. In the absence of Taut, effector and memory T-cell responses in mice are severely impaired, mainly due to increased apoptosis of effector cells. Hence, this paper provides an important link between the regulation of cell size and effector T-cell responses