This dissertation examines whether computer-mediated, text-based conversation (chat) between friends and strangers differ in efficiency and politeness over time. Experiment 1 is a longitudinal corpus collection task, which is analyzed to see if there are differences in how efficient friend and stranger dyads are at completing collaborative tasks and whether these differences persist across the three-week study. Experiment 1 participants did an online version of a traditional referential communication task (the tangram task) every week, which became practiced over time, as well as a novel puzzle task that changed every week. (Experiment 1 analysis only analyzes the tangram task data.) Experiment 2 uses stimuli taken from both tangram and puzzle tasks and looks at how third-party ‘over-reader’ judgments on politeness evolve across three weeks. Experiment 3 expands on this by systematically manipulating the dialogue taken from Experiment 1 to demonstrate that politeness is not purely determined by a speaker’s intention, as suggested by the dominant theory of politeness by Brown and Levinson (1987). The results of Experiment 1 indicate that there were few differences between the number of unique descriptive words that friend and stranger dyads used, though friends tended to take more turns than strangers. The results of Experiment 2 show that third-party over-readers are bad at explicitly distinguishing between friend and stranger dyads in both the practiced and novel tasks, though they do rate strangers as being more polite than friends at first; this difference evaporates by the second week. The results of Experiment 3 suggest that though an obviously impolite utterance will never be considered very polite (and vice versa), an interlocutor’s response to an utterance can nonetheless influence how polite an utterance sounds. Furthermore, those dyads thought to be friends are granted more flexibility in their utterances than those thought to be strangers: impolite utterances can be judged as neutral when over-readers think they are reading the conversation of friends but remains impolite when they think they are reading the conversation of strangers.