More Code, Less Understanding? On the Impact of AI Assistants on Developers’ Productivity and Code Ownership

Artificial Intelligence (AI) is transforming many domains, including software engineering. AI-based tools are gaining popularity and are increasingly being integrated into software development workflows, automating complex tasks such as code writing and reviewing. When it comes to coding tasks, some evidence suggests that tools like Copilot boost developers’ productivity (e.g.,developers can handle a larger number of pull requests per week). However, it remains unclear whether this comes at the expense of code ownership (i.e.,the developer’ ability to argue about their implementation choices). To partially address this gap, we present an experiment aimed at investigating the impact of AI-based assistants on developers’ productivity and behavior in the context of code writing (e.g.,developing a program from scratch or evolving an existing code). Our focus is on the interplay between productivity and code ownership. We asked 69 participants (34 BSc and 13 MSc students, 8 researchers, and 14 professional developers) to perform two code writing tasks, one with the support of AI and one without. Then, we compared the two treatments in terms of: (i) time spent on the coding task and percentage of the task completeness—both being productivity proxies; and (ii) ability of the participants to answer questions about the code they implemented—code ownership proxy. While the time-based analyses did not provide strong evidence on the impact of AI on the investigated dependent variables, participants using AI achieved a much higher task completeness (>2× in terms of median), confirming a positive impact on their productivity. However, such a boost did not come for free. Indeed, we also observed a loss in code ownership when participants used AI, with lower ability to answer technical questions (–12.5%).