The face of illusory truth: Repetition of information elicits affective facial reactions predicting judgments of truth

People tend to judge repeated information as more likely true compared with new information. A key explanation for this phenomenon, called the illusory truth effect, is that repeated information can be processed more fluently, causing it to appear more familiar and trustworthy. To consider the function of time in investigating its underlying cognitive and affective mechanisms, our design comprised two retention intervals. Seventy-five participants rated the truth of new and repeated statements 10 min, as well as 1 week after first exposure while spontaneous facial expressions were assessed via electromyography. Our data demonstrate that repetition results not only in an increased probability of judging information as true (illusory truth effect) but also in specific facial reactions indicating increased positive affect, reduced mental effort, and increased familiarity (i.e., relaxations of musculus corrugator supercilii and frontalis) during the evaluation of information. The results moreover highlight the relevance of time: both the repetition-induced truth effect as well as EMG activities, indicating increased positive affect and reduced mental effort, decrease significantly after a longer interval.