Context: Prior research has established that a few individuals generally dominate project communication and source code changes during software development, regardless of task assignments at project initiation. Objective: While this phenomenon has been noted, prior research has not sought to understand these dominant individuals. Previous work has found that core communicators are the gatekeepers of their teams' knowledge, and the performance of these members was correlated with their teams' success. Building on this work, we have employed a longitudinal approach to study the way core developers' attitudes, knowledge sharing behaviors and task performance change over the course of their project. Method: We first used Social Network Analysis (SNA) and standard statistical analysis techniques to identify and select artifacts and central practitioners from ten different software development teams. We then applied psycholinguistic analysis and directed content analysis (CA) techniques to interpret the content of these practitioners' messages. Finally, we inspected core developers' activities at various points in time during systems' development. Results: Among our findings, we observe that core developers' attitudes and knowledge sharing behaviors were linked to their involvement in actual software development and the demands of their wider project teams. However, core developers appeared to naturally possess high levels of insightful characteristics. Conclusion: Project performance would likely benefit from strategies aimed at surrounding core developers with other competent communicators. Core developers should also be supported by a wider team who are willing to ask questions and challenge their ideas. Finally, the availability of adequate communication channels would help with maintaining positive team climate especially in distributed developments.(Abridged)