Understanding the low inter-rater agreement on aggressiveness on the Linux Kernel Mailing List

Communication among software developers plays an essential role in open-source software (OSS) projects. Not unexpectedly, previous studies have shown that the conversational tone and, in particular, aggressiveness influence the participation of developers in OSS projects. Therefore, we aimed at studying aggressive communication behavior on the Linux Kernel Mailing List (LKML), which is known for aggressive e-mails of some of its contributors. To that aim, we attempted to assess the extent of aggressiveness of 720 e-mails from the LKML with a human annotation study, involving multiple annotators, to select a suitable sentiment analysis tool.

The results of our annotation study revealed that there is substantial disagreement, even among humans, which uncovers a deeper methodological challenge of studying aggressiveness in the software-engineering domain. Adjusting our focus, we dug deeper and investigated why the agreement among humans is generally low, based on manual investigations of ambiguously rated e-mails. Our results illustrate that human perception is individual and context dependent, especially when it comes to technical content. Thus, when identifying aggressiveness in software-engineering texts, it is not sufficient to rely on aggregated measures of human annotations. Hence, sentiment analysis tools specifically trained on human-annotated data do not necessarily match human perception of aggressiveness, and corresponding results need to be taken with a grain of salt. By reporting our results and experience, we aim at confirming and raising additional awareness of this methodological challenge when studying aggressiveness (and sentiment, in general) in the software-engineering domain.