Human Joint Transportation in a Multi-User Virtual Environment Stephan Streuber Astros Chatziastros

06/06/20162  multisensory  visually (physical environment, social environment)  somatosensory (information source, constraint)  interesting questions:  How do humans coordinate their actions with those of others in time and space?  Which information and mechanisms are important in order to coordinate actions successfully? Joint Transportation Task

06/06/20163 Which information and mechanisms are important in order to coordinate actions successfully?  Environment (e.g. common goal g)  Sensing the interaction partner (e.g. gaze)  Communication (e.g. pushing)  Task representation (e.g. walking trajectory)

06/06/20164 Interaction via Environment:  Individuals perform the task as if they would act alone. (no integration of social information)  E.g. individuals affect each others action by creating physical constraints in the environment IF ( g < threshold ) THEN compensate; Leader (no extra); Follower (all)

06/06/20165 Interaction via Sensing:  Integration of social information during Joint Action in order to maximize performance of the dyad.  Non verbal communication: gaze, eye contact, facial expressions, gesture, tonality,…  Experiment: only limited visual information: position, orientation, velocity, gaze  Prediction: Leader (no extra); Follower (all) IF ( f(g,p) < threshold ) THEN compensate;

06/06/20166 Interaction via Communication:  Exchange of information in order to communicate the common goal  Experiment: Follower could push the stretcher!  Prediction: Leader (share); Follower (share) Broadcast g; IF (g < threshold) THEN compensate;

06/06/20167 Interaction via Task Representation:  Both individuals have a representation of the particular task. (e.g. stretcher carrying)  They plan their walking paths based on this representation without necessity of integrating social cues about the interaction partner or communicating with them anymore  Prediction: Leader (share); Follower (share)

06/06/20168 Collaborative Setup

06/06/20169 Experimental Questions:  Which of the four introduced aspects of interaction are mainly involved in joint stretcher carrying? Which information is used?  What path characteristics do humans optimize depending on whether they walk individually or jointly (connected via stretcher)?

 Individual Condition (4 Trials)  12 subjects, duration experiment ca. 1,5 hours  Predictions:  Individual Condition (4 Trials)  12 subjects, duration experiment ca. 1,5 hours  extra effort = deviation from individual walking trajectory 06/06/  Joint Condition (4 Trials) Procedure: environmentsensingcommunicationrepresentation Leader and Follower share extra effort? NO YES

06/06/ m 12 m  Variables:  path length  compliance of a power law Experimental Methods top view onto the maze 12 m C-Segment

06/06/ Experimental Methods  two third power law: Established relation between curvature and end-effector velocity  hand drawing (Lacquantini, Viviani)  locomotion (Vieilledent et al.)  Assumption: Participants will obey a power law if they are not constraint by the interaction partner (the better they act like a single entity)  correlation factor between 0 and 1 vtvt vtvt R  r=0.84  v t = k∙R1/3

06/06/ Experiment 1 _ results individualjoint Power Law Compliance

06/06/ Experiment 1 _ results individualjoint Path Length Development

06/06/ Experiment 1 _ results  How do individuals share the extra effort due to the task related- cooperation in the joint action condition? environmentsensingcommunicationrepresentation Leader and Follower share extra effort? NO YES Power Law CompliancePath Length Development

06/06/ Experiment 1 _ results  How do individuals share the extra effort due to the task related- cooperation in the joint action condition? environmentsensingcommunicationrepresentation Leader and Follower share extra effort? NO YES Power Law CompliancePath Length Development

 20 subjects,  duration experiment ca. 1,5 hours  Prediction: 06/06/  Joint Condition A (physical stretcher)  Joint Condition B (virtual stretcher) Experiment 2 _ procedure communicationrepresentation Leader and Follower share extra effort? NOYES

06/06/ Experiment 2 _ results Power Law Compliance Path Length Development Physical Stretcher Virtual Stretcher Physical Stretcher Virtual Stretcher communicationrepresentation Leader and Follower share extra effort? NOYES

06/06/ Experiment 2 _ results Power Law Compliance Path Length Development Physical Stretcher Virtual Stretcher Physical Stretcher Virtual Stretcher communicationrepresentation Leader and Follower share extra effort? NOYES

06/06/ Conclusions:  The availability of visual or haptic information about the interaction partner did not effect the joint action behavior  Subjects planed their actions based on a stable representation of the task.  We did not find indication for social learning: subjects shared extra effort due to the cooperative task evenly!  high similarity of individual behavior and stretcher “behavior”

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06/06/ Thank you for your attention!

06/06/  Subject Order Effects:  Observing the interaction partner performing the task caused an improved performance in the own action!  initial role influenced behavior of leader and follower (behavioral pattern carried over into new role) P = 0.14 joint condition P < 0.05 individual condition Experiment 1 _ results

06/06/ Experimental Methods  Velocity curvature relation in walking examined before - what's new here?  neither predefined path, nor totally free movement  no simple shape of movement (ellipse), no periodic motion  analysis of connected dyads  Interpretation:  higher level control law,  central movement planning  peripheral biomechanics  optimization strategy (related to minimum jerk / maximization of smoothness)  Calculation:  correlation coefficient log(Radius); log(Velocity)  describes how accurate any power law applies  r=0.84

06/06/ Outlook