Abstract: Theory of mind (ToM) refers to understanding other's mental states, such as beliefs, intentions, emotions, and thoughts, to predict other's behaviors. ToM gradually became one of the areas of much interest among developmental psychology and cognitive neuroscience. The concept of attribution of intentions to others is a central element of ToM. In the daily life, we not only need to understand the private intention of a single person, but also have to understand the communicative intention among two or multiple persons. Understanding the communicative intention is more complex than understanding the private intention. In the current study, the event related potentials (ERPs) technology was employed to explore the dissociative electrophysiological correlates for understanding private versus communicative intention while the subjects observing three types of comic strips: 1) private intention; 2) communicative intention; 3) physical intention. We report the ERP study to investigate the time course of understanding the private intention and understanding the communicative intention. Electrophysiological results showed a significantly larger amplitude peak of N250 over the parietal sites for private intention compared to communicative and physical intentions in the 200-300 ms epoch. At a later stage (i.e., from 300-600 ms), the mean amplitudes of the late positive component (LPC) for communicative intention were more positive than those for the private and physical intentions. Furthermore, the mean amplitudes of the LPC were also significantly larger for private intention compared to the physical intention from 400-600 ms. Our data provide a direct comparison between the electrophysiological correlates for understanding the private intention as well as understanding the communicative intention. Our findings show that understanding the communicative intention overlaps the neural system capable of understanding private intention but requires the involvement of an additional system. Individuals are first able to understand a single person’s intention, and understanding the communicative intention builds on that earlier understanding by involving the same mental-state processing characteristic of understanding private intention plus an additional communicative intention processing system as well. We believe that understanding private intention and understanding the communicative intention are two different levels of ToM. Understanding the private intention is the basis for understanding the communicative intention and the level of understanding the communicative intention is higher than the level of understanding the private intention.

Key words: Theory of mind, private intention, communicative intention, social cognition, ERP