Learning and using knowledge about what other people do and don't know despite amnesia.

Successful communication requires keeping track of what other people do and do not know, and how this differs from our own knowledge. Here we ask how knowledge of what others know is stored in memory. We take a neuropsychological approach, comparing healthy adults to patients with severe declarative memory impairment (amnesia). We evaluate whether this memory impairment disrupts the ability to successfully acquire and use knowledge about what other people know when communicating with them. We tested participants in a referential communication task in which the participants described a series of abstract "tangram" images for a partner. Participants then repeated the task with the same partner or a new partner. Findings show that much like healthy individuals, individuals with amnesia successfully tailored their communicative language to the knowledge shared with their conversational partner-their common ground. They produced brief descriptions of the tangram images for the familiar partner and provided more descriptive, longer expressions for the new partner. These findings demonstrate remarkable sparing in amnesia of the acquisition and use of partner-specific knowledge that underlies common ground, and have important implications for understanding the memory systems that support conversational language.