6️⃣Our results show that surprise is used to communicate in novel interaction, reflected in behavior, physiology, and neural activity. This suggests a cognitive mechanism shaping how we develop new communication systems and has implications for human communication, AI, and human-machine interaction.

5️⃣We thought that If Receivers recognize goals through surprise, we should see neural markers of expectation violations. Indeed, EEG data shows surprise is encoded in fronto-central brain regions, linking it to cognitive processes of detecting unexpected events.

4. To provide the physiological evidence of the model, we conducted model-based analysis of receive’s PDR data. Receivers’ PDR strongly correlates with model-derived surprise—suggesting that unexpected movements grab attention and influence cognitive processing.

3️⃣The Surprise Model accurately predicts Sender’s message design and participant behavior across different samples. It outperforms models using only movement or state priors, showing that all components are essential to capture human communication!

2️⃣TCG is a two-player game where the Sender moves on a grid-creating a message, while the Receiver must infer their hidden goal based on the observed message. After analyzing hundreds of messages, we identified three distinct message types senders used to communicate.

1️⃣To test this, we built a Surprise Model with two key components. The movement component assumes motion continues in a straight line, so deviations create surprise. The state prior encodes Sender’s goal information. We tested this model in the Tacit Communication Game (TCG).

Here we proposed that without a common language, people rely on universal physical principles to build shared understanding. Once a system is established, Senders strategically defy expectations to create meaning—making surprise a powerful communicative tool.