The truth effect in relation to neuropsychological functioning in traumatic brain injury.

OBJECTIVES Individuals with traumatic brain injury may have difficulty accepting other viewpoints, but there is not yet a clinical test to measure the readiness with which one accepts new information as true. This study examined the truth effect-the tendency to rate previously seen material as being 'more true' than newly presented material-to explore whether individual differences in the truth effect can be quantified and related to memory or other neuropsychological variables, including brain injury severity. METHODS Seventy-four individuals being seen for neuropsychological assessment were asked to classify 15 semantic statements as biographical, scientific or historical and were later asked to rate 10 of the previously viewed statements and 10 new statements as either true or false. RESULTS A truth effect was clearly present in two groups which had gained familiarity with opposite sets of statements. As well, individuals with better immediate verbal memories rated more of the previously seen statements as true. CONCLUSIONS A verbal encoding factor appears to underlie the truth effect and may explain the difficulties that some TBI patients have in accepting newly presented information as true.