講演者: Robin Orthey先生（福山大学 特別研究員・Maastricht University）
日 時: 2017年8月1日（火） 15:30～17:00（延長する場合があります）
場 所: 関西学院大学上ケ原キャンパス （F号館 304教室）
Forced choice tests started out as a clinical malingering tool (known as the Symptom Validity Test) detecting whether psychological symptoms were fake or genuine. In deception detection the forced choice paradigm tests for hidden knowledge of crime relevant detail in suspects. In this paradigm a suspect is presented with a questions, for example “What was the murder weapon” and two equally plausible answer alternatives, such as “gun” and “knife”. The suspect is instructed to select the correct answer alternative or guess if they don’t know it. Truth tellers, who by definition are unaware of the correct response, have to guess on each question and therefore their total score falls within levels of chance. Empirical evidence suggests, that liars faced with this paradigm purposefully select incorrect answers, providing total scores lower than expected by chance. This is known as underperformance and is used to determine deception.
My talk shall begin with a brief introduction to Signal Detection Theory as a measure of Accuracy in psychological tests and then introduce my research project. It focuses on the different strategies liars adopt to defeat the test. To do so my team and I propose a new theoretical model that distinguished strategies based on the beliefs formed over the test mechanism. I will present a summary of my recent studies illustrating this model and in addition, I will present a specific experiment wherein, we address the issue of coaching and countermeasures in this test. Finally, my talk will end on a reflection on practical applications and the question how to determine cut off points.
Mr. Orthey talked about the psychological mechanism of the liar’s behavior when they did the forced choice test. In the forced choice test to detect deception, two words are simultaneously presented to participants: One relates knowledge of crime-relevant detail of suspects, the other does not relate one. Participants were asked to choose a word about knowledge of crime relevant detail in suspects. Previous studies showed that person who do not have knowledge of crime chose both word in approximately the same proportion (chance level). On the other hand, person who have knowledge of it avoided to select of word related the crime. His study also showed that liars avoided to select word related knowledge of crime relevant detail in suspects using the forced choice test. These facts indicated that the forced choice test is useful method of screening the suspect.
During and after his talk, audience asked him many questions, and active debate was held.