Michael R. Winograd

Review of recent studies and issues regarding the P300-based complex trial protocol for detection of concealed information

In this review, the evolution of new P300-based protocols for detection of concealed information is summarized. The P300-based complex trial protocol (CTP) is described as one such countermeasure (CM)-resistant protocol. Recent lapses in diagnostic accuracy (from 90% to 75%) with CTPs applied to mock crime protocols are summarized, as well as recent enhancements to the CTP which have restored accuracy. These enhancements include 1) use of performance feedback during testing, 2) use of other ERP components such as N200 in diagnosis, 3) use of auxiliary tests, including the autobiographical implicit association test, as leading to restored diagnostic accuracy, and 4) a study of the mechanisms underlying CMs. A novel, doubly efficient version of the CTP involving presentation of two probes in one trial is described as a new way to improve accuracy to levels above 90% in mock crime situations. Finally, a thorough analysis of the legal issues surrounding use of the CTP in U.S. is given.

The role of deception in P300 memory detection

Purpose. P300 memor yd etection test is an euroscientific procedure to assess memories stored in the brain. P300 memor yd etection can and is currently applied to assess criminal suspects on recognition of critical crime information. Contrasting memor yd etection with lie detection, researchers have argued that P300 memor y detection does not involv ed eception. We empirically investigated this argument by manipulating deception between groups. Methods. Thirty-four community volunteers participated in aP 300 memor y detection test, answering either deceptively (deceptiv ec ondition) or truthfully (truth condition) to their own name. Results. P300 memor yd etection was significant in the truth condition, indicating that deceptiv er esponding is not ap rerequisite for valid P300 memor yd etection. However, there wer ec lear indications that deceptiv er esponding improve dm emor y detection. Conclusions. Deception seems involved in the P300 memor yd etection test; and deceptiv er esponding ma ya dd to test accuracy.

The effects of asymmetric vs. symmetric probability of targets following probe and irrelevant stimuli in the complex trial protocol for detection of concealed information with P300

The complex trial protocol (CTP, [J.P. Rosenfeld, E. Labkovsky, M. Winograd, M.A. Lui, C. Vandenboom & E. Chedid (2008), The complex trial protocol (CTP): a new, countermeasure-resistant, accurate P300-based method for detection of concealed information. Psychophysiology, 45, 906-919.]) is a sensitive, new, countermeasure-resistant, P300-based concealed information protocol in which a first stimulus (Probe or Irrelevant) is followed after about 1.4-1.8 s by a Target or Non-Target second stimulus within one trial. It has been previously run with a potentially confounding asymmetric conditional probability of Targets following Probes vs. Irrelevants. This present study compared asymmetric vs. symmetric conditional probability groups and found no significant differences in detection rates or Probe-minus-Irrelevant P300 differences between groups. Group differences were seen in error rates and reaction times (RT) to second stimuli. These differences were, however, not diagnostic for deception vs. truth-telling, and were attributable to response perseveration.

Assigned Versus Random Countermeasure-Like Responses in the P300-Based Complex Trial Protocol for Detection of Deception: Task Demand Effects

We recently introduced an accurate and countermeasure resistant P300-based deception detection test called the complex trial protocol (Rosenfeld et al. in Psychophysiology 45(6):906–919, 2008). When subjects use countermeasures to all irrelevant items in the test, the probe P300 is increased rather than reduced (as it was in previous P300-based deception protocols), allowing detection of countermeasure users. The current experiment examines the role of task demand on the complex trial protocol by forcing the subject to make countermeasure-like response to stimuli. Subjects made either a simple random button response to both probe and irrelevant stimuli (experiment 1) or a more complex, assigned, button response to probe and irrelevant stimuli (experiment 2). We found that an increase in task demand reduced the effectiveness of the test. Using random responses we found a simple guilty hit rate of 11/12 with no false positives, but only a 4/11 hit rate for countermeasure-users. Using assigned responses we found a simple guilty hit rate of 8/15 with no false positives, and a 7/16 hit rate for countermeasure-users. We herein suggest that the high level of task demand associated with these countermeasure-like responses causes reduced hit rates.

The impact of prior knowledge from participant instructions in a mock crime P300 Concealed Information Test.

In P300-Concealed Information Tests used with mock crime scenarios, the amount of detail revealed to a participant prior to the commission of the mock crime can have a serious impact on a studys validity. We predicted that exposure to crime details through instructions would bias detection rates toward enhanced sensitivity. In a 2 × 2 factorial design, participants were either informed (through mock crime instructions) or naïve as to the identity of a to-be-stolen item, and then either committed (guilty) or did not commit (innocent) the crime. Results showed that prior knowledge of the stolen item was sufficient to cause 69% of innocent-informed participants to be incorrectly classified as guilty. Further, we found a trend toward enhanced detection rate for guilty-informed participants over guilty-naïve participants. Results suggest that revealing details to participants through instructions biases detection rates in the P300-CIT toward enhanced sensitivity.