Chapter Zero · Beginner FAQ

What Are "Reasoning Models" and "Deep Thinking"?

A lot of AI apps hide a Deep Thinking switch. Turn it on and the reply slows down, the bill goes up — so what are you actually buying?

One-sentence answer

A reasoning model works the problem out step by step on scratch paper, then hands in the answer. It's slower and more expensive, but it gets hard problems wrong less often. One caveat: turning on deep thinking for a simple question is using a sledgehammer to crack a nut.

What "think first, then answer" actually means

Regular mode is like a quiz-bowl buzz: the question drops, you speak from the first thing that pops into your head. Deep thinking is like a long exam question: you list the constraints on scratch paper, try a few approaches, cross out the ones that fail, and only then copy the answer onto the sheet. The so-called "thinking" is just a few extra pages of scratch work. That scratch work is generated one word at a time too — so it's slower, and it costs more.

Same puzzle · two ways to answer

Here's a small seating-logic puzzle. Tap the two buttons below and watch how each mode answers. Start with Instant mode, then try Deep-thinking mode.

Puzzle: Family dinner, one row of 5 seats. Rules: ① Grandpa hates noise, so he sits on an end; ② the two kids (Xiaoming, Xiaole) can't sit next to each other; ③ Mom sits next to Xiaoming to help with the food; ④ Dad pours the tea, so he sits dead center. How do you seat them?
Time
Cost
Which questions are worth deep thinking

The rule in one line: if the answer has to be worked out step by step, turn it on; if you can look it up or see it at a glance, leave it off. Four questions below — you judge. Tap and you'll know if you got it.

A cheap little habit: default to regular mode. When it gets something wrong, or you can feel "this one's a bit twisty," turn on deep thinking and ask again. That's the best value.

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