In this paper, we describe the influence of physical proximity on the development of collaborative relationships between scientific researchers and on the execution of their work. Our evidence is drawn from our own studies of scientific collaborators, as well as from observations of research and development activities collected by other investigators. These descriptions provide the foundation for a discussion of the actual and potential role of communications technology in professional work, especially for collaborations carried out at a distance.

In conversation speakers design their utterances to be understood against the common ground they share with their addressees-their common experience, expertise, dialect, and culture. That ordinarily gives addressees an advantage over overhearers in understanding. Addressees have an additional advantage, we pro-pose, because they can actively collaborate with speakers in reaching the mutual belief that they have understood what was said, whereas overhearers cannot. As evidence for the proposal, we looked at triples of people in which one person told another person in conversation how to arrange 12 complex figures while an over-hearer tried to arrange them too. All three began as strangers with the same background information. As predicted, addressees were more accurate at arrang-ing the figures than overhearers even when the overhearers heard every word. Other evidence suggests that the very process of understanding is different for addressees and overhearers. 8 1989 Acadermc Press, Inc. People understand each other in conversations by gathering evidence about each other’s intentions. How do they do that? The traditional view, which we will call the autonom&s view, is that they listen to the words uttered, decode them, and interpret them against what they take to be the common ground of the participants in the conversation (e.g., Anderson,

In conversation, two people inevitably know different amounts about the topic of discussion, yet to make their references understood, they need to draw on knowledge and beliefs that they share. An expert and a novice talking with each other, therefore, must assess each other's expertise and accommodate to their differences. They do this in part, it is proposed, by assessing, supplying, and acquiring expertise as they collaborate in completing their references. In a study of this accommodation, pairs of people who were or were not familiar with New York City were asked to work together to arrange pictures of New York City landmarks by talking about them. They were able to assess each other's level of expertise almost immediately and to adjust their choice of proper names, descriptions, and perspectives accordingly. In doing so, experts supplied, and novices acquired, specialized knowledge that made referring more efficient. For success in conversation, people must continually appeal to their common ground—their mutual knowledge, beliefs, and

Appelt, D. 1985c. Some pragmatic issues in the planning of definite and indefinite noun