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Erard R.E.,Psychological Institutes of Michigan
Psychological Injury and Law | Year: 2016

Confirmatory bias is an unavoidable source of error in human judgment, which is rooted in the adaptive design of the brain for recognizing meaningful patterns. In forensic psychology, the complete elimination of confirmatory bias is worth aspiring to, but even its substantial reduction is fraught with challenges. In this brief article, I present a vignette from an actual jury trial to illustrate how a seemingly small instance of confirmatory bias led to a major blunder in expert testimony. Also, I consider how it might have been prevented. © 2016 Springer Science+Business Media New York Source


Erard R.E.,Psychological Institutes of Michigan | Meyer G.J.,University of Toledo | Viglione D.J.,Alliant International University
Psychological Injury and Law | Year: 2014

Gurley et al. (Psychological Injury and Law 7:9-17, 2014) express reservations about the admissibility of testimony based on the Rorschach Performance Assessment System (R-PAS) in court. They question whether there is sufficient evidentiary foundation in the underlying psychometrics and adequate general acceptance among psychologists for R-PAS-based testimony to meet either the Daubert or Frye criteria for admissibility and also raise doubts about how well it meets the criteria for the use of forensic tests proposed by Heilbrun (Law and Human Behavior 16:257-272, 1992). This invited comment addresses their concerns about the admissibility of R-PAS-based testimony and corrects some erroneous statements about the psychometrics of R-PAS and the pertinent empirical literature. Gurley et al. characterize R-PAS as being in competition with the established Comprehensive System (CS; Exner 2003), though we clarify that it is actually an evolutionary development from the CS and designed to be a replacement for it. We also point out how their conclusion that R-PAS-based forensic testimony may be hazardous or premature is based on an insufficient familiarity with the R-PAS scientific and professional literature, a misinterpretation of the Frye and Daubert evidentiary standards, and a mischaracterization of several of Heilbrun's (Law and Human Behavior 16:257-272, 1992) criteria for the use of tests in forensic testimony. © 2014 Springer Science+Business Media New York. Source


Erard R.E.,Psychological Institutes of Michigan
Psychological Injury and Law | Year: 2012

The Rorschach Performance Assessment System (R-PAS; Meyer et al. 2011) is a new system for administering, scoring, and interpreting the Rorschach Inkblot Test that is designed to make the best possible use of currently available scientific and clinical evidence. Many features of R-PAS are well-suited to forensic evaluation generally and to psychological evaluations in psychological injury cases in particular. Among them, R-PAS: (a) offers an alternative to self-report methods that adds incremental validity, (b) provides a useful check against exaggerated or minimized symptom presentation, (d) generates evidence concerning implicit traits and behavioral tendencies, (e) offers techniques for adjusting for abnormal response sets, (f) uses internationally applicable reference data that do not exaggerate or minimize pathology, (g) organizes results according to the strength of the evidence, and (h) presents results on which are interpretations are based in a manner easy for the intelligent layperson to grasp. Despite its recent formal introduction to the professional assessment community, R-PAS takes advantage of decades of research in peer-reviewed publications (including the insights of Rorschach critics) and builds on established validity and general acceptance for most of its procedures and features. The article describes the standards and criteria applying to expert psychological testimony in U. S. federal and state courts and applies them to Rorschach-based testimony in general and R-PAS-based testimony specifically. It is argued that when the system is properly used and applied and when such testimony is appropriately formulated, it should be found admissible in both state and federal courtrooms © 2012 Springer Science + Business Media, LLC. Source


Erard R.E.,Psychological Institutes of Michigan
Psychological Injury and Law | Year: 2015

In deciding which instrument to use in making a prediction or classification, forensic psychologists strive to use the most accurate test possible for their purpose. But accuracy in prediction or classification can be measured in many different ways. Choosing the right approach to measuring accuracy requires a basic understanding of various test accuracy statistics including, most fundamentally, sensitivity, specificity, positive predictive power, and negative predictive power. These statistics and their purposes are reviewed, along with related concepts such as base rates, cut scores, and the application of Bayes’ theorem to the use of tests in particular circumstances. The advantages of using ROC (receiver operating characteristics) curves and AUC (area under the curve) statistics in choosing tests are also briefly reviewed. © 2015, Springer Science+Business Media New York. Source

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