From Fast Thinking to Deliberate Reasoning: An Analysis of System 2 Cognition in Advanced AI Models

The Cognitive Blueprint: Kahneman’s Dual Process Theory of Mind

The discourse surrounding advanced artificial intelligence has increasingly adopted a powerful explanatory framework from cognitive psychology: the dual-process theory of mind, most famously articulated by Nobel laureate Daniel Kahneman. This theory posits that human cognition operates via two distinct modes, or “systems,” which govern how we think, make judgments, and solve problems.1 Understanding this cognitive blueprint is essential for contextualizing the recent paradigm shift in AI, where models are evolving from rapid, intuitive pattern-matchers into more deliberate, analytical reasoners.

premium-career-track—head-of-cybersecurity-operations By Uplatz

Defining the Two Systems

The core of Kahneman’s thesis is the differentiation between what he terms System 1 and System 2 thinking. This is not a literal description of two separate physical parts of the brain but rather a metaphorical distinction between two types of cognitive processing that exhibit fundamentally different characteristics.1

System 1 (The Intuitive Mind): This system represents our brain’s fast, automatic, unconscious, and often emotional mode of thought.1 It operates with minimal to no voluntary effort and is the engine of our daily cognitive life, handling a vast array of tasks from the mundane to the surprisingly complex. System 1 is responsible for abilities such as determining that one object is more distant than another, localizing the source of a sound, completing a common phrase like “war and…”, or displaying disgust at a gruesome image.2 Its operations are characterized by being elicited unintentionally, requiring a very small amount of cognitive resources, and being impossible to stop voluntarily.1 For a highly trained expert, such as a chess master, System 1 can even generate a strong, intuitive move without conscious deliberation.2

A classic illustration of System 1’s function—and its fallibility—is the “bat and a ball” problem: “A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost?” For most people, the number 10 cents immediately and involuntarily springs to mind.4 This answer is a product of System 1’s rapid, associative pattern matching. It is intuitive, effortless, and incorrect.

System 2 (The Deliberative Mind): In stark contrast, System 2 is the slow, effortful, infrequent, logical, and conscious mode of thought.1 It is the cognitive machinery we engage for complex problem-solving and analytical tasks that demand focused attention and consideration. System 2 is mobilized when we perform complex computations, such as multiplying 17 by 24, look for a friend in a crowded room, or determine the validity of a complex logical argument.1 Its operations are defined by being elicited intentionally, requiring a considerable amount of cognitive resources, and being subject to voluntary control.1 This high cognitive cost makes System 2 inherently “lazy”; our brains will default to the less demanding System 1 whenever possible.4 To solve the bat and ball problem correctly, one must engage System 2 to override the initial intuitive error. By deliberately constructing the algebraic steps ($bat = ball + 1$; $bat + ball = 1.10$), one can deduce that the ball costs 5 cents.5

 

The Division of Labor and Interplay

 

System 1 and System 2 are not independent agents but partners in a highly efficient, albeit imperfect, cognitive arrangement.3 Whenever we are awake, both systems are active. System 1 runs automatically, continuously generating suggestions for System 2 in the form of impressions, intuitions, intentions, and feelings.3 System 2, typically in a comfortable low-effort mode, receives these suggestions. Most of the time, when the situation is routine and the suggestions are sound, System 2 adopts them with little or no modification. We generally believe our impressions and act on our desires, and this division of labor minimizes effort and optimizes performance.3

The critical function of System 2 emerges when System 1 runs into difficulty. It is mobilized when a question arises for which System 1 has no ready answer, as with the multiplication problem, or when an event is detected that violates the model of the world that System 1 maintains—for instance, a cat barking or a lamp jumping.3 In these moments of surprise or cognitive strain, conscious attention is surged, and System 2 is called upon to provide more detailed and specific processing to resolve the anomaly. Furthermore, System 2 is responsible for the continuous monitoring of our own behavior, a function central to self-control. It is the part of our mind that overrides the impulses of System 1, allowing us to remain polite when angry or to restore control when we are about to blurt out an offensive remark.1 In essence, most of what our conscious self (System 2) thinks and does originates in the automatic activities of System 1, but System 2 has the final word when things get difficult.3

 

Cognitive Biases and the Limits of Intuition

 

The elegant efficiency of this cognitive partnership comes with a significant vulnerability: the potential for systematic errors in judgment, known as cognitive biases.1 These biases are not random but are predictable consequences of the interplay between the two systems, particularly System 1’s reliance on heuristics, or mental shortcuts.2 Heuristics such as anchoring (relying too heavily on the first piece of information offered), availability (overestimating the likelihood of events that are more easily recalled), and framing (drawing different conclusions from the same information, depending on how it is presented) are tools of System 1 that allow for rapid decision-making.2

However, these shortcuts can lead to significant errors. The challenge is that System 2, the designated monitor, may have no clue that an error has occurred.3 Even when cues to likely errors are available, preventing them requires the enhanced monitoring and effortful activity of System 2, which is often “lazy” and disinclined to engage.3 The relationship between the systems is fundamentally governed by a principle of least effort; the brain is a “cognitive miser” that defaults to the low-energy System 1 whenever it can.4 This has a direct and profound parallel in the design of artificial intelligence. Early large language models (LLMs), much like System 1, were optimized for speed and computational efficiency, providing fast, statistically plausible answers.6 The new class of “reasoning models,” conversely, are explicitly designed to expend more computational resources at the moment of inference—a process analogous to the high metabolic cost of engaging System 2.8 The fact that these advanced models are significantly slower and more expensive to operate is not an incidental flaw but a fundamental design choice, reflecting a trade-off between “cognitive cost” and reasoning accuracy.11 This suggests that the evolution of AI is not merely a quest for greater accuracy but also a negotiation with the inherent computational costs of deliberation.

 

Emulating Deliberation: The Rise of System 2 Analogues in Artificial Intelligence

 

The dual-process theory provides a compelling lens through which to view the recent trajectory of large language model development. The industry is witnessing a deliberate engineering shift away from models that exclusively exhibit System 1-like characteristics toward a new class of models designed to emulate the slow, methodical, and analytical capabilities of System 2. This evolution marks a pivotal moment in the pursuit of more capable and reliable AI.

 

Standard LLMs as System 1 Analogues

 

Standard LLMs, particularly the feed-forward neural networks that form their architectural basis, function in a manner strikingly analogous to human System 1 cognition.5 Their core operation involves processing an input prompt and generating a response almost instantaneously. This output is not the product of conscious deliberation or logical deduction but of rapid, automatic pattern matching across the vast datasets on which they were trained.7 They excel at tasks that are intuitive and associative, such as completing a sentence, translating languages, or summarizing a document—tasks that rely on recognizing statistical regularities in language.2

However, just like System 1, this approach has inherent limitations. Standard LLMs are susceptible to replicating and amplifying biases present in their training data, leading to outputs that can be unfair or stereotypical.7 They are also prone to generating “hallucinations”—plausible-sounding but factually incorrect or nonsensical information—because they lack an intrinsic mechanism for critical self-evaluation or fact-checking.7 Their reasoning process is largely opaque, confined within a “black box” of high-dimensional correlations that are not easily interpretable, much like the unconscious operations of System 1.6

 

Reasoning Models as Nascent System 2 Analogues

 

In response to these limitations, a new category of “reasoning models,” also referred to as “long-thinking AI,” has emerged.6 The foundational principle behind these models is a departure from the paradigm of immediate response. They are explicitly designed to “spend more time thinking”—that is, to allocate additional computational resources at inference time to deconstruct and solve complex, multi-step problems.10 This deliberate, resource-intensive process is a direct analogue to the effortful and analytical nature of System 2 thinking.6

This new class of models includes OpenAI’s o-series (o1, o3), Google’s Gemini 2.0 Flash Thinking, and Anthropic’s Claude 3.7 Sonnet, which features an “extended thinking” toggle, allowing users to explicitly invoke this slower, more deliberate mode.6 The engineering goal is to translate this additional computational work into a tangible increase in accuracy and reliability, particularly on challenging tasks within the domains of mathematics, computer science, and scientific reasoning, where the intuitive, pattern-matching approach of standard LLMs consistently falls short.6

This development mirrors a key aspect of human cognition: the emergence of complex reasoning abilities. The capabilities unlocked by these new techniques are often described as “emergent,” meaning they appear only in models that have reached a sufficient scale in terms of parameters and training data.20 This is not merely a technical curiosity; it parallels the developmental trajectory in humans, where the capacity for abstract, multi-step reasoning—a hallmark of System 2—is not innate but develops over years as the brain matures and accumulates knowledge. This suggests that a certain threshold of underlying complexity and knowledge representation is a prerequisite for System 2-like functions to manifest, whether in biological or artificial systems. It implies that continued scaling of AI architectures may not just yield incremental improvements but could unlock qualitatively new cognitive functions, representing a significant vector of progress toward more general artificial intelligence.

 

A Critical Perspective on the Analogy

 

While the System 1/System 2 framework is a powerful and intuitive metaphor for understanding the evolution of LLMs, it is crucial to approach the analogy with nuance and intellectual rigor. A direct, literal equivalence between computational processes and human cognition is an oversimplification that can obscure important distinctions.19

First, the dual-process theory itself, despite its popularity, has faced criticism within the field of psychology regarding the strict dichotomy of the two systems and challenges in replicating some of the priming studies that supported it.19 Second, and more central to AI, the mechanisms underlying “long-thinking” models are fundamentally different from human consciousness and deliberation. While techniques like Chain-of-Thought prompting force a model to generate intermediate tokens, this process is still driven by the same underlying transformer architecture that predicts the next most probable token based on statistical patterns.14 It does not involve symbolic logic, subjective experience, or genuine comprehension in the human sense.7 The model is not “thinking” in the way a human does; it is executing a more complex, sequential pattern-matching task. Therefore, the analogy is best understood as a functional one: the AI behaves as if it is engaging in a more deliberate process, leading to outputs that resemble the products of human System 2 thought. It is a useful explanatory framework, not a precise model of the AI’s internal cognitive state.

 

The Algorithmic Toolkit for AI Reasoning

 

The leap from fast, intuitive outputs to deliberate, structured reasoning in AI is not a result of a single breakthrough but rather the development and integration of a sophisticated toolkit of algorithmic techniques. These methods, primarily centered on prompt engineering and novel inference strategies, provide the scaffolding necessary for large language models to deconstruct complex problems and articulate a methodical path to a solution.

 

Chain-of-Thought (CoT): The Foundation of Linear Reasoning

 

The foundational technique that unlocked this new paradigm is Chain-of-Thought (CoT) prompting, first detailed by researchers at Google in 2022.22 The concept is elegantly simple yet profoundly effective: instead of asking a model for a direct answer, the prompt is engineered to elicit a series of intermediate, natural-language reasoning steps that precede the final conclusion.20 In essence, it asks the model to “show its work” or “think out loud”.8

This approach dramatically improves performance on tasks requiring arithmetic, commonsense, or symbolic reasoning because it forces the model to break down a complex, multi-step problem into a sequence of simpler, more manageable sub-problems.20 For example, when faced with a math word problem, a standard LLM might incorrectly guess the answer based on superficial patterns. A CoT-prompted model, however, will first identify the initial quantities, calculate the intermediate results of each operation described, and then combine those results to arrive at the final answer, mirroring a human’s logical process.22 This technique has evolved into several variants:

  • Few-Shot CoT: This is the original method, where the prompt includes several hand-crafted examples (exemplars) that demonstrate the desired step-by-step reasoning process. The model then uses these examples as a pattern to follow for a new, unseen problem.21
  • Zero-Shot CoT: A surprisingly effective simplification discovered later, this method involves simply appending a phrase like “Let’s think step by step” to the end of a user’s prompt. For sufficiently large models, this simple instruction is enough to trigger a deliberative, step-by-step response without requiring any explicit examples.21
  • Automatic CoT (Auto-CoT): To overcome the manual effort of creating high-quality exemplars for few-shot CoT, this approach uses an LLM itself to automatically generate reasoning chains for a diverse set of questions, which are then used to construct the prompts for the main task.21

 

Advanced Reasoning Structures: Beyond Linearity

 

While CoT established the power of sequential reasoning, its linear, single-path nature is a significant limitation for problems where exploration or robustness is key. More advanced techniques have been developed to address this.

  • Tree of Thoughts (ToT): This framework represents a major conceptual advance over CoT by enabling non-linear exploration of a problem space.19 Instead of pursuing a single chain of thought, ToT allows the model to generate and consider multiple different reasoning paths at each step, creating a branching structure akin to a tree.26 Crucially, the model is equipped with a mechanism to self-evaluate the promise of each path, allowing it to look ahead, prioritize more viable branches, and backtrack from dead ends.26 This trial-and-error process is much closer to how humans tackle complex, open-ended, or strategic problems (like solving a Sudoku puzzle or planning a sequence of moves in a game) where a single, straightforward line of reasoning is unlikely to succeed.14
  • Self-Consistency: This technique focuses on improving the reliability and accuracy of CoT reasoning.29 It operates on the principle that while a complex problem may have multiple valid reasoning paths, they should all converge on the same correct answer.29 The method involves running the same CoT prompt multiple times with a higher “temperature” setting to encourage diverse outputs. This generates a set of different reasoning chains. The final answer is then determined by a majority vote among the outcomes of these chains.14 By relying on consensus, self-consistency mitigates the risk of a single flawed reasoning path leading to an incorrect result and has been shown to have a strong correlation between the level of consistency and the final accuracy of the answer.29

 

Grounding Reasoning in Fact: Retrieval-Augmented Generation (RAG)

 

A primary failure mode for all generative models, including those using CoT or ToT, is “hallucination”—the generation of information that is plausible but factually incorrect. Retrieval-Augmented Generation (RAG) is a framework designed specifically to combat this issue by connecting the LLM to external, authoritative knowledge sources.31

The RAG process involves two main stages. First, when a query is received, an information retrieval system searches a relevant knowledge base (e.g., a collection of internal documents, a technical manual, or the live internet) to find snippets of information pertinent to the query.31 Second, this retrieved information is appended to the original prompt and fed into the LLM, which then generates a response that is “grounded” in the provided factual context.31

In the context of advanced reasoning, RAG creates a powerful synergy. It can be integrated into the reasoning process to ensure that the individual steps within a Chain of Thought or the nodes within a Tree of Thoughts are based on verifiable facts rather than the model’s potentially flawed or outdated internal knowledge.32 This combination of structured reasoning (from CoT/ToT) and factual grounding (from RAG) leads to significantly more trustworthy and reliable outputs, especially for knowledge-intensive tasks.33

 

Comparative Analysis of Techniques

 

These distinct yet complementary techniques are not mutually exclusive. The frontier of AI research is increasingly focused on combining them into hybrid architectures that leverage the strengths of each. For instance, a system might use a Tree of Thoughts to explore potential solution strategies, with each step in each branch being fact-checked and augmented by a RAG call, and the final answer being validated through a self-consistency check. This convergence suggests a future where AI reasoning is not a monolithic process but a modular, multi-stage cognitive workflow. This workflow would mirror a comprehensive human approach to problem-solving: exploring multiple avenues (ToT), grounding each step in external facts (RAG), generating diverse arguments for each path (Self-Consistency), and structuring the entire process logically (CoT). This sophisticated, hybrid model of AI cognition moves far beyond the simple System 1/System 2 analogy, pointing toward a future of AI agents equipped with distinct, specialized modules for exploration, verification, and deliberation.

The following table provides a consolidated comparison of these core reasoning techniques.

Technique Core Mechanism Primary Use Case Strengths Weaknesses Analogy to Human Cognition
Chain-of-Thought (CoT) Generates a linear sequence of intermediate reasoning steps before the final answer. Multi-step problems in math, logic, and commonsense reasoning. Improves accuracy on complex tasks; provides interpretability into the model’s process. Linear and inflexible; can propagate errors from one step to the next; prone to hallucination. Deliberately thinking through a problem step-by-step in a single, focused line of argument.
Tree of Thoughts (ToT) Explores multiple, branching reasoning paths simultaneously, with self-evaluation and backtracking. Complex planning, strategic, or combinatorial problems with large search spaces. More flexible and robust than CoT; can solve problems where linear reasoning fails. Computationally very expensive; more complex to implement and guide. Brainstorming multiple solutions, evaluating their pros and cons, and abandoning unpromising ideas (trial and error).
Self-Consistency Generates multiple diverse reasoning chains for the same problem and selects the final answer by majority vote. Tasks with a single, verifiable correct answer (e.g., math, multiple-choice QA). Significantly increases robustness and accuracy over a single CoT; consensus correlates with correctness. Increases computational cost by a factor of the number of paths generated; less useful for open-ended creative tasks. “Sleeping on a problem” or asking multiple experts for their opinion and trusting the consensus view.
Retrieval-Augmented Generation (RAG) Retrieves relevant information from an external knowledge base and provides it to the LLM as context for generation. Fact-intensive, knowledge-based tasks requiring up-to-date or domain-specific information. Reduces hallucinations; grounds responses in verifiable facts; allows for easy knowledge updates. Performance is highly dependent on the quality of the retrieval system; can be slow due to the retrieval step. Performing research or looking up facts in a book or on the internet to inform one’s reasoning process.

 

The Vanguard of Reasoning: OpenAI’s o-Series and the Competitive Landscape

 

The theoretical advancements in AI reasoning have been swiftly operationalized by leading research labs, resulting in a new generation of commercial and experimental models. At the forefront of this movement is OpenAI with its “o-series,” a family of models explicitly designed and trained for deliberate, multi-step problem-solving. These models, along with offerings from key competitors, represent the tangible embodiment of the “long-thinking” paradigm and are setting new benchmarks for AI capability.

 

Architectural Philosophy and Training of the o-Series

 

The superior performance of the o-series is not merely the result of increased scale but stems from a fundamental shift in architectural and training philosophy.

Core Principle: Reallocating Compute: A key differentiator of the o-series is the strategic reallocation of computational resources. While the development of previous LLMs was heavily weighted toward the pre-training phase (i.e., training on massive datasets), the o-series places a much greater emphasis on the compute expended during the training and inference phases.17 Research from OpenAI has demonstrated that model performance on complex reasoning tasks scales not just with traditional metrics like parameter count, but directly with the amount of computation dedicated to the reasoning process itself—both at “train-time” (the resources used to learn how to reason) and “test-time” (the resources used to “think” when solving a new problem).9

Training Methodology: Large-Scale Reinforcement Learning: The o-series models are trained to reason using large-scale reinforcement learning (RL).9 In this training paradigm, the model is rewarded not simply for producing a correct final answer, but for generating a valid, logical, and coherent chain of thought that leads to that answer.8 This process is guided by human feedback providers who review and “grade” the AI’s intermediate reasoning steps, reinforcing effective problem-solving methodologies.8 This approach teaches the model how to solve problems in a structured way, rather than just encouraging it to mimic the statistical patterns of correct answers found in its training data.

Internal Mechanism: The “Private Chain of Thought”: When an o-series model processes a complex query, it engages in what OpenAI describes as a “private chain of thought” or a hidden “thinking block”.8 This is an internal, multi-step process where the model decomposes the problem, explores potential solution paths, evaluates intermediate steps, and self-corrects before composing and presenting the final, polished response to the user.8 This hidden deliberation is the practical implementation of “spending more time thinking.”

 

Model Deep Dive: The OpenAI o-Series Lineup

 

The o-series comprises several models, each tailored to different points on the cost-performance spectrum.

  • o1: Released in late 2024, o1 was the first model in the series and represented a significant performance leap over its predecessor, GPT-4o, especially in technical domains.17 It served as the public’s introduction to the concept of a “reasoning model.” On the SWE-bench for software engineering, o1 scored 48.9%, and on the Codeforces competitive programming benchmark, it achieved an Elo rating of 1891.11
  • o3: As the direct successor to o1, the o3 model demonstrates a substantial improvement in reasoning capabilities across all major benchmarks. It achieves a remarkable 71.7% on SWE-bench and a Codeforces Elo of 2727.11 In mathematics, its performance on the 2024 American Invitational Mathematics Examination (AIME) reached 96.7% accuracy.8 This state-of-the-art performance, however, comes with a significant computational overhead and cost, with some estimates placing the price of a single complex task in the range of $1,000.11
  • o3-mini: To address the cost and latency issues of the full o3 model, OpenAI released o3-mini, a smaller, faster, and more efficient version.8 Its most innovative feature is the introduction of a user-configurable “reasoning effort” setting (low, medium, or high).16 This allows users to dynamically trade off between response speed and analytical depth. At its “medium” effort setting, o3-mini is designed to match the performance of the much larger o1 model while delivering responses significantly faster.41
  • o3-pro: This is a specialized version of the o3 model engineered to “think longer” and allocate even more computational resources to a problem. It is recommended for the most challenging questions where reliability and accuracy are the absolute priorities, and a longer wait time is an acceptable trade-off.16

The introduction of the “reasoning effort” dial in o3-mini is more than just a technical feature; it signals a potential paradigm shift in the business model for AI. The industry may be moving from a static model, where customers purchase access to a specific model with fixed capabilities (e.g., GPT-4o), to a more dynamic one, where customers purchase “cognitive work” as a metered service. This externalizes the fundamental trade-off between cost, speed, and quality, allowing users to make that decision on a per-query basis. In this new model, companies are no longer just selling a product (the AI model) but a process (the act of reasoning). This could lead to tiered levels of “intelligence on demand,” with pricing strategies that differentiate between a “quick thought” and a “deep analysis” from the same underlying architecture.

 

The Broader Ecosystem of Reasoning Models

 

The move toward “long-thinking” AI is an industry-wide trend, not an initiative exclusive to OpenAI. Several key competitors have developed and released their own reasoning-focused models, creating a vibrant and competitive market segment.12

  • DeepSeek: This company has released its R-series of reasoning models, including DeepSeek-R1 and DeepSeek-V3, which have shown performance comparable to OpenAI’s o1 on various math, code, and reasoning tasks.10
  • Google: Google has introduced Gemini 2.0 Flash Thinking, a version of its Gemini model specifically tuned for enhanced reasoning capabilities.10
  • Anthropic: Rather than releasing a separate model, Anthropic has integrated a “thinking mode” into its Claude 3.7 Sonnet model, allowing it to function as both a standard and a reasoning LLM.6
  • xAI: Similarly, xAI’s Grok 3 model also includes a built-in thinking mode, underscoring the convergence of the industry on this hybrid approach.12

This competitive landscape validates the importance of the reasoning paradigm and is accelerating innovation as companies vie to produce models that are not only knowledgeable but also genuinely capable of complex problem-solving.

 

Quantifying the Leap: Performance on Advanced Technical Benchmarks

 

The claims of superior capability made for this new class of reasoning models are not merely qualitative. They are substantiated by a wealth of empirical data from a suite of increasingly difficult and sophisticated technical benchmarks designed to push the limits of AI performance. The results on these evaluations demonstrate a clear and often dramatic performance gap between reasoning models and their predecessors, in some cases showing AI achieving or even surpassing the level of human experts.

 

The Proving Grounds: Modern Benchmarks for AI Reasoning

 

As LLM capabilities have advanced, many of the older benchmarks used to measure progress, such as MMLU (Massive Multitask Language Understanding), are becoming “saturated,” meaning top models are approaching perfect scores, making it difficult to differentiate between them.36 In response, the research community has developed a new set of proving grounds that test not just knowledge, but the ability to apply that knowledge in complex, multi-step reasoning scenarios.

  • Science – GPQA (Graduate-Level Q&A) Diamond: This benchmark consists of PhD-level multiple-choice questions across biology, chemistry, and physics. The questions are intentionally designed to be “Google-proof,” meaning a correct answer cannot be found through simple keyword searches and instead requires deep, domain-specific understanding and reasoning.16
  • Mathematics – AIME (American Invitational Mathematics Examination): The AIME is a highly challenging mathematics competition for high school students, serving as a qualifying exam for the USA Mathematical Olympiad. Its problems require not just knowledge of theorems but creative application and multi-step logical deduction.11
  • Coding & Software Engineering – SWE-bench and Codeforces: SWE-bench is a particularly practical benchmark that evaluates a model’s ability to perform real-world software engineering tasks. It presents the model with actual, unresolved issues from open-source GitHub repositories and tasks it with generating a code patch to fix the bug.11 Codeforces is a popular platform for competitive programming contests, where a model’s performance is measured using an Elo rating system, which reflects its ability to solve novel algorithmic challenges against other competitors.11
  • General Reasoning – ARC-AGI (Abstraction and Reasoning Corpus): Created to be a better measure of general intelligence, ARC-AGI tests an AI’s ability to solve novel abstract and logical puzzles based on only a few examples. It is designed to evaluate the core AGI-like capabilities of skill acquisition and generalization from minimal data.16

 

Performance Analysis and Insights

 

The performance of reasoning models on these demanding benchmarks reveals a quantum leap in capability. The data shows a clear shift from models that are merely knowledgeable to models that are skillful.

On the 2024 AIME exams, OpenAI’s GPT-4o, a highly capable standard LLM, solved an average of only 12% of the problems. In contrast, the o1 reasoning model solved 74% on its first attempt, a figure that rose to 93% with advanced sampling techniques.36 The subsequent o3 model pushed this even higher, achieving 96.7% accuracy.11 This is not an incremental improvement; it is a transformative one.

A similar trend is evident in software engineering. On SWE-bench, o1 achieved a score of 48.9%, which was already a significant feat. Its successor, o3, improved this to 71.7%.11 This demonstrates a rapidly growing ability to understand complex codebases and perform genuine debugging tasks.

Perhaps the most significant finding is the point at which AI performance crosses the threshold of human expertise. On the GPQA Diamond benchmark, OpenAI’s o1 became the first model to surpass the accuracy of human experts holding PhDs in the relevant scientific fields.17 Similarly, on the ARC-AGI benchmark, o3 achieved a score of 87.5% on high compute, which is comparable to, and slightly exceeds, the human baseline performance of 85%.42

This pattern of results reveals a fundamental evolution. The benchmarks where reasoning models show the most profound gains are not tests of factual recall but of procedural skill—the ability to apply rules, execute algorithms, and generalize from abstract patterns to solve novel problems. This signifies a critical transition in AI from being primarily “knowledge engines,” adept at retrieving and reformulating information from their training data, to becoming “skill engines,” capable of using knowledge to perform complex tasks. This shift from knowing what to knowing how represents a much more significant step toward the long-term goal of artificial general intelligence.

The table below summarizes the performance of OpenAI’s o3 model against other state-of-the-art models on these key reasoning benchmarks.

Benchmark Metric OpenAI o3 Grok 4 Gemini 2.5 Pro GPT-5
GPQA Diamond (Science) Accuracy (%) 83.3 87.5 86.4 87.3
AIME 2025 (Math) Accuracy (%) 98.4 N/A N/A 100
SWE Bench (Coding) Accuracy (%) N/A 75.0 N/A 74.9
Humanity’s Last Exam (Overall) Score 20.32 25.4 21.6 35.2

Note: Data as of late 2024/early 2025 from model providers and independent evaluations. “N/A” indicates data was not available in the provided sources for that specific model-benchmark combination. SWE Bench scores are for top agentic models, where o3 was not listed in the direct comparison table.48

 

Governance and Foresight: The Ethics and Safety of Deliberative AI

 

The emergence of AI systems with advanced, human-like reasoning capabilities represents a profound technological inflection point. While these models unlock unprecedented opportunities for scientific discovery, industrial innovation, and complex problem-solving, they also introduce a new and more complex landscape of ethical and safety challenges. As AI transitions from a tool that provides information to one that performs autonomous, multi-step reasoning, the frameworks for its governance and the foresight required to manage its risks must evolve in tandem.

 

Built-in Safeguards: The Concept of Deliberative Alignment

 

In recognition of these elevated risks, developers of reasoning models are engineering novel safety paradigms directly into the models’ architecture. A leading example is OpenAI’s “deliberative alignment,” a technique specifically designed for the o-series.11

Unlike previous safety methods that primarily focused on training a model to refuse to answer prompts that violate safety policies, deliberative alignment leverages the model’s core reasoning ability for safety itself. When presented with a potentially problematic prompt, the model is trained to first engage in an internal chain-of-thought process where it explicitly reasons about its human-written safety specifications and how they apply to the user’s request.11 Only after this internal deliberation does it generate a response. This process of “reasoning about the rules before acting” has made the o-series models significantly more robust against sophisticated “jailbreak” attempts designed to circumvent safety filters, showing marked improvements over predecessors like GPT-4o.11

However, this very mechanism introduces a subtle paradox. The transparency that makes these models’ reasoning interpretable and allows for techniques like deliberative alignment also creates a new potential attack surface. While an explicit chain of thought provides a window into the model’s process for developers to debug and align 22, it also exposes that process to malicious actors. A sophisticated adversary could potentially analyze the model’s safety deliberations to identify logical flaws, biases, or loopholes in its application of the safety policy. This represents a higher-order attack, targeting not the model’s final output but the reasoning process that governs it. This creates a fundamental tension between interpretability for the purpose of safety and security against adversarial analysis, a challenge that will be central to the field of AI safety going forward.

 

The Evolving Risk Landscape

 

The increased autonomy and capability of reasoning models amplify existing AI risks and introduce new ones.

  • Accountability and Liability: When a standard LLM produces a factual error, the consequences are often limited. But when a reasoning model autonomously executes a complex, multi-step task—such as writing and deploying code, conducting a scientific analysis, or providing detailed legal or medical advice—the potential for harm is far greater. If such a system makes a critical error, determining responsibility becomes a complex legal and ethical problem. This creates a potential “accountability gap” where it is unclear whether the user, the developer, or the deploying organization is liable for the AI’s actions.15
  • Malicious Use: The same capabilities that allow these models to solve legitimate software engineering problems could be turned toward developing novel malware or identifying and exploiting security vulnerabilities on a massive scale. Their advanced reasoning could be used to devise more sophisticated and personalized disinformation campaigns or to plan complex criminal activities.54
  • Unforeseen Consequences and Control: As these systems become more complex, their behavior can become less predictable. The risk of “emergent” capabilities—abilities that were not explicitly programmed or anticipated by the developers—grows, which could lead to unintended and potentially harmful outcomes.15 The fundamental “black box” nature of neural networks remains a challenge; even with an explicit chain of thought, the underlying reasons for why the model chose one reasoning step over another can remain opaque, making full control and trust elusive.6
  • Broader Societal Harms: The immense computational power required for “long-thinking” raises significant environmental concerns due to high energy consumption.53 Issues of data privacy, the potential for hyper-personalization to create social polarization, and the economic disruption caused by the automation of high-skill cognitive labor are also magnified by these more capable systems.15

 

The Trajectory Towards AGI and Future Impact

 

The development of robust System 2-like reasoning is widely seen as a critical milestone on the path toward Artificial General Intelligence (AGI)—a hypothetical future AI with human-level cognitive abilities across a wide range of domains.11 While current reasoning models are still narrow and specialized, they demonstrate a foundational capacity for the kind of flexible, multi-step problem-solving that is a prerequisite for more general intelligence.

The continued advancement of this technology promises to have a transformative impact across numerous sectors:

  • Science and Research: AI reasoners will become indispensable partners in scientific discovery. They can accelerate research by generating novel hypotheses, analyzing vast and complex datasets, designing experiments, and even writing the code to execute them, dramatically shortening the cycle of discovery.18
  • Healthcare: In medicine, these models can assist clinicians with complex diagnostics by synthesizing and reasoning over a patient’s entire medical history, including medical records, lab reports, and radiological images, to identify patterns and suggest potential diagnoses that a human might miss.18
  • Finance: The finance industry will leverage advanced reasoning for more sophisticated risk assessment models, real-time fraud detection that can understand complex transactional patterns, and strategic planning that can simulate and evaluate the potential outcomes of different market scenarios.18

In conclusion, the advent of reasoning models marks the beginning of a new chapter in artificial intelligence. By emulating the deliberate, analytical processes of human System 2 thinking, these systems are transcending the limitations of their pattern-matching predecessors. While this leap in capability brings with it a host of complex ethical and safety challenges that demand urgent and ongoing attention, it also opens the door to a future where AI can serve as a powerful tool to help solve some of humanity’s most complex and pressing problems.