P300 Scalp amplitude distribution as an index of deception in a simulated cognitive deficit model

Truth-telling (Truth) and simulated malingering (Malinger) groups were test ed in a matching-to-sample procedure in which each sample three-digit numbe r was followed by a series of nine test numbers, only one of which matched the sample. P300 was recorded during test-number presentation. Group analys es revealed differences between the P300s of the groups in unsealed amplitu de, but not latency, in response to match and mismatch stimuli. P300 amplit udes at Fz, Ct, and Pt were scaled to remove possible confounding effects o f amplitude in tests of the interactions of site with other variables. Sign ificant interactions of both stimulus-type (match vs. mismatch) and group ( Truth vs. Malinger) with site were obtained. Within the Malinger group, a s ignificant interaction was obtained (scaled data) between site and response type (honest vs, dishonest). These interactions suggest that deceptive and honest responding are associated with different neurogenerator sets or dif ferent sets of P300-overlapping components. In within-individual analyses, 100% of the Truth participants and 87% of the Malinger participants were fo und to have larger P300 responses at Pt to match stimuli than to mismatch s timuli on the basis of intra-individual bootstrap tests. This represents an improvement in comparison with our related, previous report on a matching- to-sample test using only one test stimulus per sample. (C) 1999 Elsevier S cience B.V. All rights reserved.