Piotr Słowiński

Kinematic characteristics of motion in the mirror game

We present the analysis of data collected in the mirror game setting. In our set-up two players are asked to mirror each other movements (with or without a designated leader). First, we study kinematic characteristics of motion of individual players, and next we investigate how they are affected by interactions between the players. Results of the presented analysis will be used to inform the design of interactive virtual players with kinematics based on the similarity principle.

Design of a Virtual Player for Joint Improvisation with Humans in the Mirror Game.

Joint improvisation is often observed among humans performing joint action tasks. Exploring the underlying cognitive and neural mechanisms behind the emergence of joint improvisation is an open research challenge. This paper investigates jointly improvised movements between two participants in the mirror game, a paradigmatic joint task example. First, experiments involving movement coordination of different dyads of human players are performed in order to build a human benchmark. No designation of leader and follower is given beforehand. We find that joint improvisation is characterized by the lack of a leader and high levels of movement synchronization. Then, a theoretical model is proposed to capture some features of their interaction, and a set of experiments is carried out to test and validate the model ability to reproduce the experimental observations. Furthermore, the model is used to drive a computer avatar able to successfully improvise joint motion with a human participant in real time. Finally, a convergence analysis of the proposed model is carried out to confirm its ability to reproduce joint movements between the participants.

Design and Validation of a Virtual Player for Studying Interpersonal Coordination in the Mirror Game

The mirror game has been recently proposed as a simple, yet powerful paradigm for studying interpersonal interactions. It has been suggested that a virtual partner able to play the game with human subjects can be an effective tool to affect the underlying neural processes needed to establish the necessary connections between the players, and also to provide new clinical interventions for rehabilitation of patients suffering from social disorders. Inspired by the motor processes of the central nervous system (CNS) and the musculoskeletal system in the human body, in this paper we develop a novel interactive cognitive architecture based on nonlinear control theory to drive a virtual player (VP) to play the mirror game with a human player (HP) in different configurations. Specifically, we consider two cases: 1) the VP acts as leader and 2) the VP acts as follower. The crucial problem is to design a feedback control architecture capable of imitating and following or leading an HP in a joint action task. The movement of the end-effector of the VP is modeled by means of a feedback controlled Haken–Kelso–Bunz (HKB) oscillator, which is coupled with the observed motion of the HP measured in real time. To this aim, two types of control algorithms (adaptive control and optimal control) are used and implemented on the HKB model so that the VP can generate a human-like motion while satisfying certain kinematic constraints. A proof of convergence of the control algorithms is presented together with an extensive numerical and experimental validation of their effectiveness. A comparison with other existing designs is also discussed, showing the flexibility and the advantages of our control-based approach.

Unravelling socio-motor biomarkers in schizophrenia

We present novel, low-cost and non-invasive potential diagnostic biomarkers of schizophrenia. They are based on the ‘mirror-game’, a coordination task in which two partners are asked to mimic each other’s hand movements. In particular, we use the patient’s solo movement, recorded in the absence of a partner, and motion recorded during interaction with an artificial agent, a computer avatar or a humanoid robot. In order to discriminate between the patients and controls, we employ statistical learning techniques, which we apply to nonverbal synchrony and neuromotor features derived from the participants’ movement data. The proposed classifier has 93% accuracy and 100% specificity. Our results provide evidence that statistical learning techniques, nonverbal movement coordination and neuromotor characteristics could form the foundation of decision support tools aiding clinicians in cases of diagnostic uncertainty.Mirror game test could detect schizophreniaA new test of movement and social interaction could detect markers of schizophrenia, and help to diagnose and manage the condition. In an effort to establish reliable indicators of schizophrenia, Piotr Slowinski at the University of Exeter, UK and colleagues developed a test that could detect deficits in movement and social interactions, both characteristics of the disorder. They asked people to perform movements alone, and to mirror the movements of a computer avatar or a humanoid robot. Automated analysis of the movements allowed to distinguish people with schizophrenia from healthy participants with accuracy and specificity slightly better than clinical interviews and comparable to test based on much more expensive neuroimaging methods. The technique could help with diagnosis of schizophrenia and to monitor patients’ responses to treatment, but needs to be tested in clinical trials before being applied in clincal practice.

Beyond in-phase and anti-phase coordination in a model of joint action

In 1985, Haken, Kelso and Bunz proposed a system of coupled nonlinear oscillators as a model of rhythmic movement patterns in human bimanual coordination. Since then, the Haken–Kelso–Bunz (HKB) model has become a modelling paradigm applied extensively in all areas of movement science, including interpersonal motor coordination. However, all previous studies have followed a line of analysis based on slowly varying amplitudes and rotating wave approximations. These approximations lead to a reduced system, consisting of a single differential equation representing the evolution of the relative phase of the two coupled oscillators: the HKB model of the relative phase. Here we take a different approach and systematically investigate the behaviour of the HKB model in the full four-dimensional state space and for general coupling strengths. We perform detailed numerical bifurcation analyses and reveal that the HKB model supports previously unreported dynamical regimes as well as bistability between a variety of coordination patterns. Furthermore, we identify the stability boundaries of distinct coordination regimes in the model and discuss the applicability of our findings to interpersonal coordination and other joint action tasks.

Mode structure of a semiconductor laser with feedback from two external filters

We study a semiconductor laser subject to filtered optical feedback from two separate filters. This work is motivated by an application where two fiber gratings are used to stabilize the output of a laser source. Specifically, we consider the structure of the external filtered modes (EFMs), which are the basic cw-states of the system. The system is modelled by a set of four delay differential equations with two delays that are due to the travel times of the light in each of the external cavities. Here, each filter is approximated by a Lorentzian and we assume that there is no interaction between the two filters. We derive a transcendental equation for the EFMs as a function of the widths, detunings and the feedback strengths of the two filters. With continuation techniques we investigate how the number of EFMs changes with parameters. In particular, we consider the equation for its envelope. This allows us to determine regions in the plane of the two detunings that correspond to one, two or three EFM components - disjoint closed curves that are traced out by the EFMs as a function of the feedback phase.

Influence of Facial Feedback and Mind Perception During a Cooperative Human-Robot Task in Schizophrenia

Rapid progress in the area of humanoid robots offers tremendous possibilities for investigating and improving social competences in people with social deficits, but remains yet unexplored in schizophrenia. In this study, we examined the influence of social feedbacks elicited by a humanoid robot on motor coordination during a human-robot interaction. Twenty-two schizophrenia patients and twenty-two matched healthy controls underwent a collaborative motor synchrony task with the iCub humanoid robot. Results revealed that positive social feedback had a facilitatory effect on motor coordination in the control participants compared to non-social positive feedback. This facilitatory effect was not present in schizophrenia patients, whose social-motor coordination was similarly impaired in social and non-social feedback conditions. Furthermore, patients’ cognitive flexibility impairment and antipsychotic dosing were negatively correlated with patients’ ability to synchronize hand movements with iCub. Overall, our findings reveal that patients have marked difficulties to exploit facial social cues elicited by a humanoid robot to modulate their motor coordination during human-robot interaction, partly accounted for by cognitive deficits and medication. This study opens new perspectives for comprehension of social deficits in this mental disorder.

Solution structure and dynamics of a semiconductor laser subject to feedback from two external filters

We present an analysis of a semiconductor laser subject to filtered optical feedback from two filtering elements (2FOF). The motivation for this study comes from applications where two filters are used to control and stabilise the laser output. Compared to a laser with a single filtered optical feedback loop, the introduction of the second filter significantly influences the structure of the basic continuous-wave solutions, which are also known as external filtered modes (EFMs). We compute and represent the EFMs of the underlying delay differential equation model as surfaces in the space of frequency ωs and inversion level Ns of the laser, and feedback phase difference dCp. The quantity dCp is a key parameter since it is associated with interference between the two filter fields and, hence, controls the effective feedback strength. We further show how the EFM surface in (ωs, dCp, Ns)-space changes upon variation of other filter parameters, in particular, the two delay times. Overall, the investigation of the EFM-surface provides a geometric approach to the multi-parameter analysis of the 2FOF laser, which allows for comprehensive insight into the solution structure and dynamics of the system.

Percolation Operators and Related Models

Here we review the theory and methods of the two basic stochastic models with absorbing states: percolation operators and contact processes. We explore connections between them by studying discrete-time approximations of a continuous-time contact processes. In particular, we look at the approximations based on both synchronous and asynchronous updating schemes. Additionally, we go on to discuss several individual-based models, which are commonly used to model different biological phenomena. Specifically, we focused on models with absorbing states that, have spatially non-homogenous stationary states, or that have shown to be bi-stable. More generally, we aim to demonstrate the challenges associated with reconciling different mathematical descriptions of natural phenomena.

Effects of time-delay in a model of intra- and inter-personal motor coordination

Abstract Motor coordination is an important feature of intra- and inter-personal interactions, and several scenarios — from finger tapping to human-computer interfaces — have been investigated experimentally. In the 1980s, Haken, Kelso and Bunz formulated a coupled nonlinear two-oscillator model, which has been shown to describe many observed aspects of coordination tasks. We present here a bifurcation study of this model, where we consider a delay in the coupling. The delay is shown to have a significant effect on the observed dynamics. In particular, we find a much larger degree of bistablility between in-phase and anti-phase oscillations in the presence of a frequency detuning.