Most research on text-based synchronous computer-mediated communication (SCMC) in language learning has used output logs as the sole data source. I review interactionist and sociocultural SCMC research, focusing in particular on the question of technological determinism, and conclude that, from whichever perspective, reliance on output logs leads to an impoverished picture of the experience of SCMC users and of phenomena relevant to learning. The assumption that output logs are an adequate data source fails to give due weight to the specificities of this form of communication, in particular the constraints and affordances of the computer interface. I examine the potential contribution of other data sources, providing by way of illustration an analysis of sample eye-tracker data from a tandem SCMC session. (Contains 1 figure, 4 tables, and 9 notes.)