AI Coding Assistants May Slow Down Experienced Developers, Surprising New Study Reveals
A groundbreaking study released by the AI research nonprofit METR has challenged prevailing assumptions about the benefits of AI-powered code assistants. Contrary to the common belief that tools like Cursor can accelerate software development, the study found that experienced developers working in familiar codebases were actually 19% slower when using these AI assistants.
🚨 Key Findings from the METR Study
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Expectation vs. Reality Gap:
Developers expected AI to cut task time by 24%. Even after using the assistant, they reported a perceived 20% speedup. The reality? On average, tasks took 19% longer—a substantial slowdown. -
Experienced Developers Hit Hardest:
The productivity decline was observed among developers working with open-source projects they already knew well. Rather than helping, the AI often disrupted their mental models and workflows, introducing friction instead of flow. -
Researchers Surprised:
Lead authors Joel Becker and Nate Rush expressed genuine surprise, stating that the initial expectation was for a twofold productivity boost—a result that not only didn’t materialize but reversed entirely in key cases.
⚖️ Balancing Perspectives: When AI Helps… and When It Doesn’t
Despite the METR study’s sobering conclusions, other research paints a more optimistic view:
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Boost for Repetitive Tasks:
Tools like GitHub Copilot and Cursor can accelerate mundane coding—e.g., writing boilerplate code, generating comments, or formatting syntax—especially helpful for junior developers or during prototyping. -
Knowledge Sharing & Onboarding:
AI assistants can act as interactive documentation, helping new team members understand best practices and integrate more quickly into development workflows. -
Varied Impact Across Teams:
According to GitLab and McKinsey reports, productivity improvements of up to 45% have been noted—but context matters. Simple CRUD tasks benefit more than nuanced architecture decisions or legacy code refactoring. -
Skepticism from Engineering Leaders:
Only about 6% of tech leaders report significant productivity gains from AI tools, with many teams seeing only marginal benefits—or none at all.
đź§ Implications for the Future of Software Development
The METR study raises vital questions for teams considering broad AI adoption:
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Integration Over Imitation:
AI tools must evolve to enhance expert workflows, not mimic them. Disrupting well-honed practices can create drag rather than lift. -
Rethinking Tool Design:
AI assistants might need better contextual understanding, smarter prompting mechanisms, and deeper domain training to be effective in real-world, high-stakes environments. -
Changing Job Landscape:
While AI may slow senior developers in certain settings, it could replace or augment junior roles, shifting the structure of engineering teams and the nature of entry-level programming jobs.
📌 Final Thoughts: More Complexity Than Hype Admits
The conversation around AI in development is no longer about whether it helps, but when, how, and for whom. The METR study is a reminder that tools don’t replace experience—and that meaningful productivity gains depend on careful implementation and continuous learning.
As the industry navigates this AI-powered transition, one thing is clear: blind optimism must give way to evidence-based integration strategies.
Sources:
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METR Study (2025): https://metr.org/blog/2025-07-10-early-2025-ai-experienced-os-dev-study/
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Channel News Asia: https://www.channelnewsasia.com/business/ai-slows-down-some-experienced-software-developers-study-finds-5231866
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Full Scale Dev Team: https://fortegrp.com/insights/ai-coding-assistants
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GitLab, McKinsey, LeadDev Survey, TechRadar, Reddit discussions