Observers' decision moment in deception detection experiments: Its impact on judgment, accuracy, and confidence

Research into the nonverbal detection of deception has typically been conducted by asking observers to judge whether a number of videotaped statements are truthful or deceptive. In most cases, the behavioural segments used in this research have been very short. A typical result is that observers tend to judge the statements as truthful (truth bias). In the present experiment, observers watched a series of video clips showing senders answering three questions about an event that they had witnessed. Observers had to indicate whether each sender's statement was truthful or deceptive, their judgmental confidence, and when they had made their decision about the sender's credibility: during his or her first, second, or third answer. Competing predictions were made about the influence of the decision moment on the observers' judgments and accuracy. The results replicated most research findings reported in the US and North‐European literature, including the truth bias phenomenon. However, the proportion of judgments of truthfulness decreased as observers decided later, particularly for the deceptive statements. This yielded an increase in accuracy in judging deceptive accounts. These results are consistent with the idea that initial credibility judgments are made heuristically, either because there is not enough information available or because observers are in the first, automatic stage of current attribution and person perception models. Heuristic decision making may produce a high proportion of judgments of truthfulness. Later judgments would be made in a systematic manner. The truth bias detected in deception research may be caused by researchers having used very brief and uninformative behavioural samples. The moment when observers made their decision had only a marginal negative influence on confidence.