Impacts of Human Robot Proxemics on Human Concentration-Training Games with Humanoid Robots

The use of humanoid robots within a therapeutic role, that is, helping individuals with social disorders, is an emerging field, but it remains unexplored in terms of concentration training. To seamlessly integrate humanoid robots into concentration games, an investigation into the impacts of human robot interactive proxemics on concentration-training games is particularly important. In the case of an epidemic diffusion especially—for example, during the COVID-19 pandemic—HRI games may help in the therapeutic phase, significantly reducing the risk of contagion. In this paper, concentration games were designed by action imitation involving 120 participants to verify the hypothesis. Action-imitation accuracy, the assessment of emotional expression, and a questionnaire were compared with analysis of variance (ANOVA). Experimental results showed that a 2 m distance and left-front orientation for a human and a robot are optimal for human robot interactive concentration training. In addition, females worked better than males did in HRI imitation games. This work supports some valuable suggestions for the development of HRI concentration-training technology, involving the designs of friendlier and more useful robots, and HRI game scenarios.

The role of social signals in segmenting observed actions in eighteen-month-old children

Learning about actions requires children to identify the boundaries of an action and its units. Whereas some action units are easily identified, parents can support children’s action learning by adjusting the presentation and using social signals. However, currently little is understood regarding how children use these signals to learn actions.In the current study we investigate the possibility that communicative signals are a particularly suitable cue for segmenting events. We investigated this hypothesis by presenting 18-month-old children (N=60) with short action sequences consisting of toy animals either hopping or sliding across a board into a house, but interrupting this two-step sequence either(a) using an ostensive signals as a segmentation cue, (b) using a non-ostensive segmentation cue, and (c) without additional segmentation information between the actions.Marking the boundary using communicative signals increased children’s imitation of the less salient sliding action. Imitation of the hopping action remained unaffected. Crucially, marking the boundary of both actions using a non-communicative control condition did not increase imitation of either action. Communicative signals might be particularly suitable in segmenting non-salient actions that would otherwise be perceived as part of another action or as non-intentional. These results provide evidence of the importance of ostensive signals at event boundaries in scaffolding children’s learning.

Action imitation via trajectory-based or posture-based planning

Movement imitation is a significant daily activity involved in social interaction and motor learning. Although imitation remains poorly understood, recent research suggests that it may be achieved in two distinct ways. In posture-based imitation, movements reproduce how the body should look and feel, and are sensitive to the relative positioning of body parts. In trajectory imitation, movements mimic the spatiotemporal motion path of the end effector. We hypothesized that people can imitate via either mechanism. If true, we would expect to see a switch cost when individuals change from one mechanism to the other. To test this, twenty-five healthy young adults performed a sequential multitasking imitation task. Participants were first instructed to pay attention to the limb postures or the hand path of a video-recorded model. They next performed an intervening motor task that was neutral, congruent, or incongruent with the instructed imitation type. Finally, participants imitated the modeled movement. Spatiotemporal imitation accuracy was greatest after a neutral intervening task, and worst after posture matching. When the primary task involved imitating trajectories, we observed a switch cost: movements following the posture-matching intervening task were less consistent with baseline (neutral) performance, suggesting performance was disrupted by the incongruence. Incongruent primary and intervening tasks also reduced cross-subject consistency. Such effects were not observed when imitating limb postures. In summary, we observed a partial dissociation between posture matching and trajectory imitation as a result of instructions and intervening tasks that is nevertheless consistent with the existence of two computationally distinct imitation mechanisms.

Inhibitory Theta Burst Stimulation Highlights the Role of Left aIPS and Right TPJ during Complementary and Imitative Human–Avatar Interactions in Cooperative and Competitive Scenarios

Competitive and cooperative interactions are based on anticipation or synchronization with the partner’s actions. Both forms of interaction may either require performing imitative or complementary movements with respect to those performed by our partner. We explored how parietal regions involved in the control of imitative behavior (temporo-parietal junction, TPJ), goal coding and visuo-motor integration (anterior intraparietal sulcus, aIPS) contribute to the execution of imitative and complementary movements during cooperative and competitive interactions. To this aim, we delivered off-line non-invasive inhibitory brain stimulation to healthy individuals’ left aIPS and right TPJ before they were asked to reach and grasp an object together with a virtual partner by either performing imitative or complementary interactions. In different blocks, participants were asked to compete or cooperate with the virtual partner that varied its behavior according to cooperative or competitive contexts. Left aIPS and right TPJ inhibition impaired individuals’ performance (i.e., synchrony in cooperative task and anticipation in competition) during complementary and imitative interactions, respectively, in both cooperative and competitive contexts, indicating that aIPS and TPJ inhibition affects own-other action integration and action imitation (that are different in complementary vs imitative interactions) more than action synchronization or anticipation (that are different in cooperative vs competitive contexts).

The left ventral premotor cortex is involved in hand shaping for intransitive gestures: evidence from a two-person imitation experiment

The ventral premotor cortex (PMv) is involved in grasping and object manipulation, while the dorsal premotor cortex (PMd) has been suggested to play a role in reaching and action selection. These areas have also been associated with action imitation, but their relative roles in different types of action imitation are unclear. We examined the role of the left PMv and PMd in meaningful and meaningless action imitation by using repetitive transcranial magnetic stimulation (rTMS). Participants imitated meaningful and meaningless actions performed by a confederate actor while both individuals were motion-tracked. rTMS was applied over the left PMv, left PMd or a vertex control site during action observation or imitation. Digit velocity was significantly greater following stimulation over the PMv during imitation compared with stimulation over the PMv during observation, regardless of action meaning. Similar effects were not observed over the PMd or vertex. In addition, stimulation over the PMv increased finger movement speed in a (non-imitative) finger–thumb opposition task. We suggest that claims regarding the role of the PMv in object-directed hand shaping may stem from the prevalence of object-directed designs in motor control research. Our results indicate that the PMv may have a broader role in ‘target-directed’ hand shaping, whereby different areas of the hand are considered targets to act upon during intransitive gesturing.

Pantomime and imitation in great apes

This paper assesses great apes’ abilities for pantomime and action imitation, two communicative abilities proposed as key contributors to language evolution. Modern great apes, the only surviving nonhuman hominids, are important living models of the communicative platform upon which language evolved. This assessment is based on 62 great ape pantomimes identified via data mining plus published reports of great ape action imitation. Most pantomimes were simple, imperative, and scaffolded by partners’ relationship and scripts; some resemble declaratives, some were sequences of several inter-related elements. Imitation research consistently shows great apes perform action imitation at low fidelity, but also that action imitation may not represent a distinct process or function. Discussion focuses on how findings may advance reconstruction of the evolution of language, including what great apes may contribute to understanding ‘primitive’ forms of pantomime and imitation and how to improve their study.