How OpenAI’s o1 Series Redefines Complex Reasoning and AI Safety

What is OpenAI o1?

OpenAI released the o1 series, a new family of language models designed for complex reasoning. These models use reinforcement learning to generate long internal chains of thought before responding, allowing them to think more deeply and improve performance on difficult tasks.

How strong is o1?

In the 2024 International Olympiad in Informatics (IOI), a fine‑tuned o1 version scored 213 points with 50 attempts per problem, placing it in the top 49% of human participants. With 10,000 attempts per problem it would achieve 362.14 points, surpassing the gold‑medal threshold.

o1 also ranks in the top 89% on Codeforces competitive programming, and ranks among the top 500 U.S. students on the American Invitational Mathematics Examination (AIME) pre‑selection.

Compared with GPT‑4o, o1 shows improvements across subjects such as math, science, English, law, and economics.

Released models

o1 : Not yet publicly available.

o1‑preview : An early version accessible to ChatGPT paid users and Tier‑5 API customers.

o1‑mini : A faster, more cost‑effective model suited for tasks that require reasoning but not extensive world knowledge.

OpenAI o1 principles

o1 is trained with reinforcement learning to perform complex reasoning. Before answering, it generates a long internal chain of thought, effectively “thinking” like a human. This approach teaches the model to refine its reasoning, explore alternative strategies, and recognize its own errors.

The large‑scale reinforcement‑learning algorithm teaches the model to use its thought chain efficiently, a scaling‑law‑like effect distinct from traditional pre‑training limits.

Model evaluation

OpenAI benchmarked o1 against GPT‑4o on a variety of human exams and machine‑learning tests. The results show o1 outperforming GPT‑4o on most reasoning tasks, achieving higher scores on MMLU sub‑categories, GPQA‑Diamond, and MMMU, and matching or exceeding human expert performance on several benchmarks.

Chain of Thought

Similar to humans, o1 employs a chain‑of‑thought process to solve problems, breaking down difficult steps into simpler ones, correcting errors, and trying alternative methods, which dramatically boosts its reasoning ability.

Coding ability

After additional training, the o1‑ioi model achieved 213 points on the 2024 IOI, comparable to the top 49% of human contestants, and could reach 362.14 points with unlimited attempts. In simulated Codeforces contests, o1‑preview scored an Elo of 808 (top 11% of humans), while o1 achieved an Elo of 1807, outperforming 93% of competitors.

Human preference evaluation

Human evaluators preferred o1‑preview over GPT‑4o on reasoning‑heavy categories such as data analysis, coding, and mathematics, though GPT‑4o was favored for some natural‑language tasks.

Safety

Chain‑of‑thought reasoning provides new avenues for safety and alignment. Integrating safety policies into the model’s reasoning improves robustness, with o1‑preview showing significant gains on jailbreak and strict internal safety benchmarks.

OpenAI also conducted extensive red‑team testing, observing that chain‑of‑thought reasoning helps mitigate unsafe behavior.

Implicit Chain of Thought

OpenAI sees implicit chains as a monitoring opportunity, allowing insight into the model’s internal reasoning without exposing raw chains to users, balancing user experience, competitive advantage, and safety considerations.

OpenAI o1‑mini

o1‑mini is a smaller, faster, and cheaper model optimized for STEM reasoning. It retains most of o1’s performance on math and coding benchmarks while being 80% cheaper than o1‑preview.

On the AIME math competition, o1‑mini scored 70.0%, comparable to o1’s 74.4% and far above o1‑preview’s 44.6%.

In Codeforces, o1‑mini achieved an Elo of 1650, close to o1’s 1673 and well above o1‑preview’s 1258. It also performed well on HumanEval and CTF challenges.

On reasoning‑intensive academic benchmarks (e.g., GPQA, MATH‑500), o1‑mini outperformed GPT‑4o, though it lagged behind on tasks requiring broad world knowledge.

How to use OpenAI o1

ChatGPT Plus and Team users can select o1‑preview or o1‑mini within ChatGPT, with usage limits of 30 and 50 requests per week respectively. API access is initially granted to Tier‑5 users (spending over $1,000 on the OpenAI API) with a rate limit of 20 RPM.

Future outlook

OpenAI plans to continue iterating on the o1 series, enhancing reasoning capabilities, alignment with human values, and adding features such as web browsing, file, and image uploads to broaden applications across science, coding, mathematics, and related fields.