Collaborative discourse facilitates efficient communication and new learning in amnesia.

In previous work we reported robust collaborative learning for referential labels in patients with hippocampal amnesia, resulting in increasingly rapid and economical communication or "common ground" with their partners [Duff, M. C., Hengst, J., Tranel, D., & Cohen, N. J. (2006). Development of shared information in communication despite hippocampal amnesia. Nature Neuroscience, 9(1), 140-146]. The current paper reports the results of discourse analysis, describing the communicative resources and practices used in extended, repeated collaborative interactions, as partners successfully referenced the target cards, managed the task itself, and engaged in non-task talk. Although amnesic pairs showed a normal rate of reduction across trials in the number of words and time-to-completion, their communicative effort was higher overall, particularly the discourse associated with task management, they exhibited a general lack of flexibility in their referential expressions, and they showed a number of striking differences in use of personal and communal knowledge and of multiple perspectives. The interactive sessions provided a potent learning environment, but also a very challenging task in the face of memory impairment. The results give insight into the acquisition of common ground and the manner in which amnesic patients accommodate their memory deficits during real-world interactions, and they have significant implications for memory intervention.