ABSTRACT Context: General knowledge transfer is often considered a valuable effect or side-effect of pair programming, but even more important is its role for the success of the pair programming session itself: The partners often need to explain an idea to carry the process forward. Goal: Understand the mechanisms at work when knowledge is transferred during a pair programming session; provide practical advice for constructive behavior. Method: Qualitative data analysis of recordings of actual industrial pair programming sessions. Results: Some pairs are much more efficient in their knowledge transfer than others. These pairs manage to (1) not attempt to explain multiple things at once, (2) not lose sight of a topic, (3) clarify difficult points in stages. Conclusions: Pair programming requires skill beyond software development skill. To be able to identify knowledge needs and then push such knowledge to or pull it from the partner successfully is one aspect of such skill. We characterize a number of its elements.
