BACKGROUND AND AIM: Gait kinematics are influenced by the emotional state [1] or the emotional context [2]. Observers recognize emotions from the whole body motion [1,3]. We investigated the influence of emotions on the kinematics of interactions between two walkers. We focused on the specific case of walking together. METHODS: 2 professional actors walked in an 8m circular area. They were first asked to walk alone in a neutral or angry emotional state. Then they walked simultaneously: individually or together. For these 2 situations, either both actors had a neutral emotional state or one or both of them experienced angriness with variations: transitive or not (Tr/NTr) and with or without talking (D/ND). Alone and individual situations were used as controlled tasks. Each task was 1' long and repeated 3 times. We focused on walking speed, relative angle and distance between actors. RESULTS: In neutral state, walking speed depended on the situation (H=8.9, p<0.05). It was slower when actors walked together: neutral gait may not be modified by the presence of another walker but by the interaction itself. No difference was observed between the 3 situations for one angry actor (NTr-ND). Nevertheless, when walking together the actor in neutral state walked faster when the other was angry NTr-ND (U=1114, p<0.001). The neutral actor may adapt his speed to follow the angry actor. For together situation, results showed that walking speed was slower when angriness was transitive (U=38472, p<0.001) or when actors spoke (U=35713, p<0.001) and faster when both actors were angry (U=36792, p<0.001). Moreover, the distance between actors was higher when angriness was transitive (U=14406, p<0.001) and when both actors were angry (U=21214, p<0.001) and lower when they spoke (U=21377, p<0.001). There was no difference between relative angles when both actors were neutral or angry NTr-ND but when only one actor was angry NTr-ND, he walked ahead. When one actor was angry, he also walked more ahead in NTr variation compared to Tr one (U=7553, p<0.001). CONCLUSIONS: This preliminary study suggests leader-follower interactions depending on emotions when two humans walk together. These interactions are expressed by relative positions and walking speed adaptations. A neutral walker accelerates to follow an angry one (NTr-ND) and this latter walks ahead as if he leads the motion. Distance between walkers is increased when both of them experience transitive angriness. This may indicate that personal spaces are adapted with respect to the perceived risk that should be enhanced with the combination of negative emotions towards the other. Future work will extend analysis to more participants and investigate the influence of other emotions and their variations on interactions while walking. ACKNOWLEDGEMENTS: This study was funded by the FP7 European project Tango. 1 Gross et al. Hum Mov Sci In press 2 Gelat et al. Neurosci Lett 497: 64-67,2011 3 Kadone et al. ISPGR2009