title: Kinematics fingerprints of leader and follower role-taking during cooperative joint actions.
abstract: Performing online complementary motor adjustments is quintessential to joint actions since it allows interacting people to coordinate efficiently and achieve a common goal. We sought to determine whether, during dyadic interactions, signaling strategies and simulative processes are differentially implemented on the basis of the interactional role played by each partner. To this aim, we recorded the kinematics of the right hand of pairs of individuals who were asked to grasp as synchronously as possible a bottle-shaped object according to an imitative or complementary action schedule. Task requirements implied an asymmetric role assignment so that participants performed the task acting either as (1) Leader (i.e., receiving auditory information regarding the goal of the task with indications about where to grasp the object) or (2) Follower (i.e., receiving instructions to coordinate their movements with their partner's by performing imitative or complementary actions). Results showed that, when acting as Leader, participants used signaling strategies to enhance the predictability of their movements. In particular, they selectively emphasized kinematic parameters and reduced movement variability to provide the partner with implicit cues regarding the action to be jointly performed. Thus, Leaders make their movements more "communicative" even when not explicitly instructed to do so. Moreover, only when acting in the role of Follower did participants tend to imitate the Leader, even in complementary actions where imitation is detrimental to joint performance. Our results show that mimicking and signaling are implemented in joint actions according to the interactional role of the agent, which in turn is reflected in the kinematics of each partner.
authors.affiliation: Department of Psychology, University of Rome "Sapienza", Via dei Marsi 78, 00185 Rome, Italy. lucia.sacheli@uniroma1.it
authors.forename: Lucia Maria
authors.initials: LM
authors.lastname: Sacheli
authors.forename: Emmanuele
authors.initials: E
authors.lastname: Tidoni
authors.forename: Enea Francesco
authors.initials: EF
authors.lastname: Pavone
authors.forename: Salvatore Maria
authors.initials: SM
authors.lastname: Aglioti
authors.forename: Matteo
authors.initials: M
authors.lastname: Candidi
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D003299:Cooperative Behavior; D005260:Female; D005385:Fingers / Q000294:innervation*; D005556:Form Perception / Q000502:physiology; D006040:Goals; D006225:Hand / Q000294:innervation; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007100:Imitative Behavior / Q000502:physiology*; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D014953:Wrist / Q000294:innervation; D055815:Young Adult