Joint Attention and Dynamics Repertoire in Coupled Dynamical Recognizers Takashi Ikegami and Hiroyuki Iizuka Department of General Systems Sciences, Graduate School of Arts and Sciences, University of Tokyo 3-8-1 Komaba, Tokyo 153-8902 {ikeg,ezca}@sacral.c.u-tokyo.ac.jp Abstract A coupled dynamical recognizer is proposed as a model for simulating turn-taking behavior. An agent is modeled as a mobile robot with two wheels. A recurrent neural network is used to produce the motor outputs. By controlling this, agents compete to take turns on a two dimensional arena. By using the genetic algorithm technique, we show that turn-taking behavior is developed between two agents. It is worth noting that turn- taking is established with a variety of dynamics. A coupling between agents is sensitive to the dynamics and we discuss the sensitivity by referring to Trevarthen’s double monitor experiments. 1 Intersubjectivity and Joint Atten- tion Here in this paper, we propose a simulation study of joint attention via coupled dynamical recognizers. There are many ways to understand psychological phenomena not directly by studying human behavior but by computer simulations and robot experiments (e.g. B.Scassellati (1999), K. Dautenhahn (1999)). To bridge between sim- ulation studies and psychology, we think it worth dis- cussing some key concepts such as joint attention and in- tersubjectivity as a Rosetta stone. 1)Joint attention: Joint attention requires a coordinated preverbal behav- ior among 2 or more persons. A simple example is a chil- dren’s pointing under the attention of the mother. It is a process of sharing one’s experience of observing an ob- ject or events with others by following pointing gestures or eye gazing. We distinguish two types of joint attention (R.Uno and T.Ikegami (2002)). If a person uses joint attention as a tool to achieve a goal (e.g. establishing the joint attention to let your dog pick up a ball), we call it ”instrumental joint attention”. But if a person takes joint attention it- self as a goal, we call it ”participatory joint attention”. For example, two looking at the same sunset establish the participatory joint attention as it doesn’t require further achievements. 2)Intersubjectivity: Intersubjectivity is to share mental states and intentions with others. Trevarthen , who first noticed its importance, classified two types of intersubjectivity. A primary inter- subjectivity is found in between an infant and a caretaker. It is thought that there exists an innate ability to orangize intersubjectivity. From around 7 months old, a secondary intersubjectivity develops. It starts to involve a third ob- ject or event besides person-person relationship. This sec- ondary intersubjectivity is thus close to instrumental joint attention in many ways. It is clear from the above definitions that intersubjec- tivity is a close concept of joint attention. Here we re- alize that to study turn-taking as objective realization of those concepts. We see that intersubjectivity can be taken as a form of interaction between subjects without ex- plicitly referring to sensory-motor coordination. On the other hand, turn-taking behavior is often taken as a mere sensory-motor coordination between subjects without re- ferring to its intersubjectivity. A glue between intersub- jectivity and turn-taking is given by joint attention. In par- ticular, behavior of participatory joint attention has both aspects of sensory-motor coordination and intersubjectiv- ity. We also think that the synchrony in preverbal interac- tion (i.e. turn-taking) triggers the emergence of intersub- jectivity via joint attention. In order to clarify the interrelation between joint atten- tion, intersubjectivity and turn-takings, we introduce an- other notion, i.e. novelty. Joint attention is, not always but, something to do with surprise and expectation. A kind of “novelty” attracts other person to engage in com- munication. It is known and used in developmental stud- ies that infants watch longer at the new/surprising events (M.Legerstee (2001)). Namely, novelty also attracts in- fants to the new event and thus interaction between in- fants and event is established. We use such novelty as un- predictability as a necessary factor to start and maintain interaction.