  Deception detection in conversations is a challenging yet important task,
having pivotal applications in many fields such as credibility assessment in
business, multimedia anti-frauds, and custom security. Despite this, deception
detection research is hindered by the lack of high-quality deception datasets,
as well as the difficulties of learning multimodal features effectively. To
address this issue, we introduce DOLOS\footnote {The name ``DOLOS" comes from
Greek mythology.}, the largest gameshow deception detection dataset with rich
deceptive conversations. DOLOS includes 1,675 video clips featuring 213
subjects, and it has been labeled with audio-visual feature annotations. We
provide train-test, duration, and gender protocols to investigate the impact of
different factors. We benchmark our dataset on previously proposed deception
detection approaches. To further improve the performance by fine-tuning fewer
parameters, we propose Parameter-Efficient Crossmodal Learning (PECL), where a
Uniform Temporal Adapter (UT-Adapter) explores temporal attention in
transformer-based architectures, and a crossmodal fusion module, Plug-in
Audio-Visual Fusion (PAVF), combines crossmodal information from audio-visual
features. Based on the rich fine-grained audio-visual annotations on DOLOS, we
also exploit multi-task learning to enhance performance by concurrently
predicting deception and audio-visual features. Experimental results
demonstrate the desired quality of the DOLOS dataset and the effectiveness of
the PECL. The DOLOS dataset and the source codes are available at
https://github.com/NMS05/Audio-Visual-Deception-Detection-DOLOS-Dataset-and-Parameter-Efficient-Crossmodal-Learning/tree/main.
