chaTree: An oTree addon allowing face-to-face communication in online group experiments

For online group experiments, we present an oTree addon that allows to include face-to-face communication in the form of a video chat. The addon is easy to use, exhibits a lean design, and allows to record communication patterns. • Many decisions are taken by groups rather than individuals. • Online experiments are well-suited to study group behavior. • chaTree allows group members to communicate face-to-face in online experiments. • This note explains how to use chaTree in experiments programmed in oTree. • The tool is easy to use and also allows to record communication patterns.