Tiago Santos

Denis Helic, Tiago Santos

Millions of users visit Stack Overflow regularly to ask community for answers to their programming questions. However, like many other platforms, Stack Overflow consistently struggles with low user retention and declining levels of user contributions to the platform. With the introduction of ChatGPT in November 2022, these ongoing difficulties on Stack Overflow were further magnified, as many users moved toward ChatGPT for programming help. In this paper, we build upon recent research on this phenomenon by analyzing the transformation of user-generated content on Stack Overflow during the post-ChatGPT period. Specifically, we analyze two years of Stack Overflow data and fit multiple causal regression models to estimate the effect of ChatGPT on the length and difficulty of user questions and code examples. We confirm an acceleration of decline in user contributions but find that ChatGPT had a significant positive effect on question and answer length, code length, and question difficulty on Stack Overflow across programming languages. Our results suggest that ChatGPT has effectively raised the bar for questions on Stack Overflow, as users increasingly turn to crowdsourced platforms for help with more complex and challenging problems. With our work we contribute to the ongoing discussion on the impact of tools such as ChatGPT on help-seeking in programming and, more broadly, on collaborative knowledge creation. Our results provide actionable insights for platform operators to support information management and user retention in the aftermath of ChatGPT's launch.

Tiago Santos, Florian Lemmerich, Denis Helic

As a tool for capturing irregular temporal dependencies (rather than resorting to binning temporal observations to construct time series), Hawkes processes with exponential decay have seen widespread adoption across many application domains, such as predicting the occurrence time of the next earthquake or stock market spike. However, practical applications of Hawkes processes face a noteworthy challenge: There is substantial and often unquantified variance in decay parameter estimations, especially in the case of a small number of observations or when the dynamics behind the observed data suddenly change. We empirically study the cause of these practical challenges and we develop an approach to surface and thereby mitigate them. In particular, our inspections of the Hawkes process likelihood function uncover the properties of the uncertainty when fitting the decay parameter. We thus propose to explicitly capture this uncertainty within a Bayesian framework. With a series of experiments with synthetic and real-world data from domains such as "classical" earthquake modeling or the manifestation of collective emotions on Twitter, we demonstrate that our proposed approach helps to quantify uncertainty and thereby to understand and fit Hawkes processes in practice.