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title: What It Means for an LLM to Reason
seo_title: What It Means for an LLM to Reason — video
description: What reasoning means for a language model, what o1 and DeepSeek R1 added, and why evaluating reasoning requires looking at steps, cost and failure modes.
keywords: reasoning models, LLM reasoning, chain of thought, CoT, OpenAI o1, test time compute, AI reasoning, illusion of thinking, Apple reasoning paper, chains of thought
date: '2026-04-08T00:00:00+00:00'
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    <div class="s5-video-watch__crumbs"><a href="https://5sigmas.com/en/videos/">All videos</a><span>Reasoning</span><span>0:58</span></div>
    <h1>What It Means for an LLM to Reason</h1><p>What reasoning means for a language model, what o1 and DeepSeek R1 added, and why evaluating reasoning requires looking at steps, cost and failure modes.</p>
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    <div class="s5-video-watch__snippet-grid"><article><span>01</span><h2>1. What &quot;reasoning&quot; means for a human</h2><p>In cognitive psychology, reasoning is a deliberate process that allows people to solve problems outside the patterns they already know. It differs from pattern recognition—which is fast,…</p></article>
<article><span>02</span><h2>2. What LLMs can do that looks like reasoning</h2><p>LLMs can perform actions that, in practical terms, produce outputs similar to human reasoning in many contexts.</p></article>
<article><span>03</span><h2>3. The birth of reasoning models: OpenAI o1</h2><p>In September 2024, OpenAI released o1, the first model explicitly designed to &quot;think before answering.&quot; The difference from earlier models was not simply model size or training data, but…</p></article></div>
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  <section class="s5-video-watch__related" aria-labelledby="related-videos-title"><div class="s5-video-watch__section-head"><span class="s5-eyebrow">Next step</span><h2 id="related-videos-title">Related videos</h2></div><div class="s5-video-watch__related-grid"><article><a href="https://5sigmas.com/en/videos/series/modelos-razonadores/05-riesgos/"><img src="https://5sigmas.com/en/series/modelos-razonadores/05-riesgos.jpg" alt="" loading="lazy" width="1280" height="720"><span>Reasoning · 1:00</span><strong>Reasoning Risks and Production Controls</strong></a></article>
<article><a href="https://5sigmas.com/en/videos/series/modelos-razonadores/04-latencia-streaming/"><img src="https://5sigmas.com/en/series/modelos-razonadores/04-latencia-streaming.jpg" alt="" loading="lazy" width="1280" height="720"><span>Reasoning · 0:59</span><strong>Latency, Streaming and Product Design</strong></a></article>
<article><a href="https://5sigmas.com/en/videos/series/modelos-razonadores/03-test-time-compute/"><img src="https://5sigmas.com/en/series/modelos-razonadores/03-test-time-compute.jpg" alt="" loading="lazy" width="1280" height="720"><span>Reasoning · 1:00</span><strong>Test-Time Compute</strong></a></article></div></section>
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