Towards Language Acquisition by an Attention-Sharing Robot

II I! II II II Towards Language Acquisition by an Attention-Sharing Robot Hideki Kozima Akira Ito Communications Research Laboratory 588-2, Iwaoka-cho, Iwaoka, Nishi-ku, Kobe 651-2401, Japan {xkozima, ai}@crl, go. jp Abstract This paper describes our preliminary research on "attention-sharing" in infants' language ac- quisition. Attention-sharing is the activity of paying one's attention to someone else's atten- tional target. This enables one to observe oth- ers' sensory-input (what they are perceiving from the target) and motor-output (what they are doing in response to the target). Being inspired by lack of attention-sharing in autis- tic children, we assumed that observation of others' behavior by attention-sharing plays an indispensable role in symbol acquisition. As a test-bed for attention-sharing, we are de- veloping a robot that can follow people's at- tentional targets by means of monitoring their gaze-direction. 1 Introduction Machine acquisition of natural language is one of the most challenging targets of cognitive science. As a basis for language acquisition, we deal with acqui- sition of a symbol system, which articulates things and events in the world into categories and gives phonological labels to the categories. The relation- ships between the categories and labels are arbitrary conventions shared by people, so that infants have to learn them through interaction with people. This paper describes the role of "attention-shar- ing" (Baron-Cohen, 1995), especially that based on gaze, in infants' symbol acquisition. Figure 1 il- lustrates how attention-sharing is achieved: self (S) captures gaze-direction of an agent (A), then the self searches in the direction and identifies the target (T). Shared attention spotlights things and events being mentioned and makes the communication co- herent about the same target. 2 Attention-Sharing and Symbol Acquisition Observation of others' verbal behavior provides in- fants with learning data for symbol acquisition. Let us consider that an agent, looking at a cat, says "cat", as illustrated in Figure 2. In order to mimic this verbal behavior, the self has to observe the (1) capture gaze Figure 1. (2) identify the target Attention-sharing based on gaze. 0 = "cat" o'1/z' ® Figure 2. Observing other's verbal behavior. I' O' I' O' Figure 3. Introducing mediators between I/O. agent's sensory-input I (stimulus from the cat) and motor-output O (verbal response) and to make the association between them. Attention-sharing enables us to observe someone else's input and output, as also shown in Figure 2. Attention-sharing guarantees that I' (the self's in- put) resembles I, since both are paying attention to the same target. At the gaze-capturing stage (Fig- ure 1, left), the self can observe the agent's output O and map it onto the self's motor image Oq (We assume an innate mapping mechanism like imitation of facial gestures by neonates.) Although thus observed relationships between in- put space and output space may vary in many ways (size, color, tone, volume, etc.), one can construct an efficient mediator between these spaces. As illus- trated in Figure 3, the complex relationships (left) Kozima and 1to 245 Language Acquisition by an Attention-Sharing Robot Hideki Kozima …

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