This study explored whether learners’ head movement and interhead distance could serve as behavioral cues related to learners’ internal states in small-group collaborative discussions: understanding, willingness to participate, and psychological safety. Eighteen science and engineering university students (in six groups of three) participated in discussions. A ceiling-mounted depth camera continuously measured their head movements during 20 min sessions. After their discussions, the participants watched the video recordings and rated their internal states per 1 min segment. Two groups were excluded due to head recognition errors caused by hand gestures, so the analysis focused on data from the four remaining groups. No consistent correlations were found across all learners or groups. However, some individuals and groups showed positive or negative correlations between internal states and behavioral indicators. Additionally, spikes in head movement often coincided with movements such as laughter, posture adjustments, and gesturing. These findings highlight the potential of bodily behavior as cues for understanding discussion dynamics. Future work will address measurement and environmental issues to elucidate these relationships better, promoting the reliable estimation of internal states from bodily behavior.