Financial Incentive does not Affect P300 in the Complex Trial Protocol (CTP) Version in Concealed Information Test (CIT) in Malingering DetectionUninstructed Subjects

Abstract

Introduction. Well-known research showed that the skin conductance response (SCR) of the Autonomic Nervous System (ANS) in the Concealed Information Test (CIT) is typically increased in participants who are financially and motivationally incentivized to beat the CIT (the paradoxical “motivational impairment” effect). This is not what happens with Reaction Time (RT)-based CITs, P 300 CITs based on the 3-stimulus protocol, nor on the P 300 -based complex trial protocol for detection of malingering. In the Concealed Information Test (CIT), there are at least two kinds of stimuli randomly presented regarding order to participants: The (1) probes are the items expected to be remembered; they are often from a crime scene in a forensic scenario—such as, a stolen diamond necklace. The (2) irrelevant stimuli are other comparably valuable items (a watch, a bracelet, a broach, etc.) which are from the same category as the probe (jewelry), but are not identical to it, so are unrecognized by the thief as the stolen item. The probe is recognized, and therefore elicits a larger physiological response in only the knowledgeable participant. To innocent suspects, the probe is just another irrelevant so elicits a smaller or no physiological response. Purpose. To determine how financial compensation affect P 300 in the Complex Trial Protocol (CTP) Version in Concealed Information Test (CIT) in malingering detection. Methods. P 300 measured P 300 peak to the subsequent negative peak {“peak to peak”) from Fz, Cz, and Pz, was recorded, filtered, artifacted, and averaged. Signals were passed through a Mitsar 19 channel (model 201) amplifier with a.16 Hz high pass filter setting, and low pass filters at 30 Hz. Output was conveyed to a 16-bit Mitsar Analog to Digital converter sampling at 500 Hz. For analyses and displays, single sweeps and averages were digitally filtered; the filter passed frequencies from 0 to 6 Hz using a Kaiser filtering algorithm. The present report study of motivated malingerers instructed how to beat the test, with uninstructed motivated (paid and unpaid) and unmotivated (“simple malingering”) subjects, using episodic and semantic memory probes. The Test of Memory Malingering (TOMM) validated behavioral differences among groups. Results. The present reports found the lack of financially motivated influence with both episodic and semantic memory stimuli. Also semantic memory-evoked P 300 s exceeded episodic memory evoked P 300 s. An effect of specific test-beating instructions was found to enhance the CIT effect for semantic information. Originality. The “Concealed Information Test (CIT) effect” (probe-minus-irrelevant P 300 differences) did not differ among incentive groups. Conclution. P300 amplitude is associated with the amount of focused attention to stimuli. This suggests that since a financial incentive should increase attention, the incentive manipulation should also produce larger P 300 s to familiar stimuli. However, once attention is enough to assure recognition of probes within a memory type category, the resulting P 300 s consequently generated in a more all-or-none manner are no longer influenced by motivation. Apparently, in the present study, attention to stimuli was adequate to assure recognition, whose consequent P 300 s, were no longer modifiable by motivation.