Definition
AI reasoning is when an AI model works through a problem step by step before giving an answer, rather than producing a response in a single instant pass.
At a glance
- A standard model answers in one quick pass; a reasoning model first works through hidden steps, then answers[5].
- The hidden working is called chain-of-thought; the extra effort per question is test-time compute[1].
- It helps most on multi-step tasks (math, planning, analysis) and little on simple lookups[3].
- The cost is real: answers can run 20 to 80 percent slower and pricier per query.
How it works
A standard model blurts out a plausible answer in one fast pass. A reasoning model pauses to break the problem into steps, weigh options, and check itself first[2]. More thinking generally means better answers on hard problems.
When to use it
Use reasoning for genuinely complex work; keep a fast standard model for quick facts and short replies. Models vary hugely in price and speed, so a common pattern is routing: cheap model for the easy majority, reasoning model only for the few hard questions[4].
Bottom line
Reasoning buys accuracy on hard problems with extra time and money; use it only where the task earns it.