Prosodic characteristics of deceptive picture descriptions in Finnish: Acoustics, beliefs, self-evaluations, and deception theories

• The purpose of this study was to compare the prosody of lies and truths in spoken Finnish. • The more nervous the participant was while lying, the lower the average pitch was, and their pitch range was narrower. • In deceptive speech, increased nervousness was correlated with an increase in number of pauses, while perceived success correlated negatively. • Those participants who thought they succeeded in deception produced fewer filled pauses and hesitations. Psycholinguistic research has sought to find reliable cues of deception in speech, but the results have been mixed. Prosody varies between individuals, situations, and languages, which makes comparisons difficult, and research designs also differ considerably. We examined vocal cues that distinguish deceptive from truthful speech in Finnish by analyzing acoustic-prosodic features collected from 20 native Finnish speakers in a neutral, low-stakes picture description setting. Using a within-subject design, participants were randomly assigned to start with either the deceptive or truthful task. Additionally, we studied whether acoustic-prosodic features correlated with participants’ beliefs about deception cues and their experiences of motivation, success, and nervousness during the deceptive task. We found that lying increased pitch range and mean intensity, and there was a higher number of repetitions in addition to a decrease in minimum pitch and response latency. Participants who believed speech variability would increase in deceptive speech exhibited an increase. Further, the average pitch was positively correlated with self-reported success but inversely correlated with nervousness. However, filled pauses showed opposite results. Our findings support some aspects of both attempted control and cognitive load theories. Contradictory to some previous studies, we did not find a consistent increase in pitch and response latency in deceptive speech. Instead, individual variations in speech prosody were linked to subjective perceptions of nervousness and success. Additionally, neither attempted control nor cognitive load theory offers a comprehensive explanation of changes we observed. We conclude that further research is needed in different contexts and languages.