P300-based detection of concealed autobiographical versus incidentally acquired information in target and non-target paradigms

The basic rationale of P300-based tests of concealed information compares responses to critical (‘probe’) and non-critical (‘irrelevant’) items. Accuracy, both in the laboratory and the field, is the degree to which responding to probes exceeds that to irrelevants. The present laboratory study assessed the influence of two factors on accuracy. The first, varied between subjects, was whether the paradigm included probes, irrelevants, and target items (as is the case in most P300 preparations), or whether the paradigm included only probe and irrelevant items. The second, orthogonally varied, within-subject factor was whether the probe was an autobiographical item (the subject's name), or incidentally acquired (as in common field applications). Accuracy was greater with the subject's name as probe, perhaps because of the greater potency of autobiographical items than incidentally acquired ones, even when these are learned to a 100% accuracy. On the other hand, contrary to expectations from a work-load interpretation, the removal of the target did not affect accuracy, but rather decreased P300 magnitude to both probes and irrelevants in the non-target group.