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Reasoning Models Can Be Effective Without Thinking (arxiv.org)
21 points by mfiguiere on Apr 16, 2025 | hide | past | pdf | 2 comments on HN

In plain words: The model skips step-by-step thinking, answers directly, then makes many answers and picks the best. With equal token budgets, it beat the usual thinking on seven reasoning tasks, 51.3 vs. 28.9 on a math set, and matched thinking up to 9 times slower.

Abstract

Recent LLMs have significantly improved reasoning capabilities, primarily by including an explicit, lengthy Thinking process as part of generation. In this paper, we question whether this explicit thinking is necessary. Using the state-of-the-art DeepSeek-R1-Distill-Qwen, we find that bypassing the thinking process via simple prompting, denoted as NoThinking, can be surprisingly effective. When controlling for the number of tokens, NoThinking outperforms Thinking across a diverse set of seven challenging reasoning datasets--including mathematical problem solving, formal theorem proving, and coding--especially in low-budget settings, e.g., 51.3 vs. 28.9 on ACM 23 with 700 tokens. Notably, the performance of NoThinking becomes more competitive with pass@k as k increases. Building on this observation, we demonstrate that a parallel scaling approach that uses NoThinking to generate N outputs independently and aggregates them is highly effective. For aggregation, we use task-specific verifiers when available, or we apply simple best-of-N strategies such as confidence-based selection. Our method outperforms a range of baselines with similar latency using Thinking, and is comparable to Thinking with significantly longer latency (up to 9x). Together, our research encourages a reconsideration of the necessity of lengthy thinking processes, while also establishing a competitive reference for achieving strong reasoning performance in low-budget settings or at low latency using parallel scaling.

Wenjie Ma, Jingxuan He, Charlie Snell, Tyler Griggs, Sewon Min, Matei Zaharia
arXiv:2504.09858 · cs.AI, cs.CL · submitted Apr 14, 2025
abstract · pdf · html · 33 pages, 7 main figures, 2 tables

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I'm not entirely sure how this kind of study jives well with other study, such as "Reasoning models don't always say what they think" [0], discussion [1].

To quote the article:

  We can’t be certain of either the “legibility” of the Chain-of-Thought (why, after all, should we expect that words in the English language are able to convey every single nuance of why a specific decision was made in a neural network?) or its “faithfulness”—the accuracy of its description. There’s no specific reason why the reported Chain-of-Thought must accurately reflect the true reasoning process; there might even be circumstances where a model actively hides aspects of its thought process from the user.
So if we can't trust the reasoning, then what's the point of checking whether they are "effective" or not?

[0]: https://www.anthropic.com/research/reasoning-models-dont-say...

[1]: https://news.ycombinator.com/item?id=43572374

> When controlling for the number of tokens, NoThinking outperforms Thinking across a diverse set of seven challenging reasoning datasets

Interesting. I thought the "thinking" was useful because it pulls in a lot of concepts into the context, but I guess not then?

It has also been said before that the text a model outputs during its Thinking step isn't actually a view into its inner thoughts. There are times when the model will think X but eventually answer Y.

But even so: the models _are_ better, right? So is the Thinking step then mostly useful during training?