Abstract: Complex Trial Protocol (CTP) is a P300-based concealed information test. It proved effective and accurate with autobiographical information (Hit rate: 92-100%; Rosenfeld at al., 2008) and mock crime (Hit Rate: 83-100%) experiments. In CTP protocol, each trial contains two stimuli: 1) A “Probe” (P--a relevant to the subject item (his/her birthday) or “Irrelevant” (I--any date, NOT relevant to the subject) and later, 2) A “Target” (T, an item with “assigned significance”) or “Non-Target” (NT, item without any specific meaning) The two stimuli are separated by about 1s. First, a date is presented (“Probe” or “Irrelevant”), then after about 1s, a string of numbers(11111) is presented ,T) or one of 4 NTs. Subject responds to first stimulus with an “I saw it” response button, whether P or I. Later, S makes T or NT button press. The current study examines countermeasures use during CTP with 5-button random response testing. Subjects were to execute an extra 5-button random response as soon as they see first stimuli (P or I).This replaces the “I saw it response,” but functions similarly. Subjects were also instructed to implement mental countermeasures for different number of irrelevant stimuli. Thus, there were groups with 1, 2, 3, and 4 (of 4) countered Irrelevants, and group with 5 countermeasures (to all 4 Irrelevants and the Probe).

Elena B. Labkovsky¹, J. Peter Rosenfeld

¹Northwestern University

Keywords: ERP , P300 , Detection of Deception , Malingering