Unlike human reasoning in abstract conceptual spaces, large language models (LLMs) typically reason by generating discrete tokens at each step, then discard the rich semantic information contained in the output distribution. Recent work such as Soft Thinking has shown that LLMs’ latent reasoning via soft concepts is a promising direction, but LLMs are trained on discrete tokens, leaving the continuous concept space underutilized during training. To address this, we propose Soft Concept Mixing (SCM), a soft concept aware training scheme that directly exposes the model to soft representations during training. Specifically, SCM constructs a soft concept vector by forming a probability-weighted average of embeddings. Then, this vector is mixed into the model’s hidden states, which embody rich contextual information. Finally, the entire latent reasoning process is optimized with Reinforcement Learning (RL). Experiments on six reasoning benchmarks demonstrate that SCM improves the reasoning performance of LLMs, and simultaneously maintains a stable training dynamic.

Current fine-grained error analyses by LLMs gain more and more attention in machine translation, but these analyses do not ground the errors to the reasons why the annotated text spans are erroneous. If LLMs do not know such reasons, the corrections or refinements by LLMs will be untrustworthy.In this paper, we check whether LLMs know such reasons in translation error grounding task. We manually build an evaluation resource through a bi-directional grounding scheme. In the forward direction, we annotate the explanation of the reason for each error span. In the backward direction, we annotate the error span given its explanation, in which the error span is masked. If the error spans of both directions are consistent, we deem the explanation is valid. Such grounding process can regulate the explanation so as to avoid the subjective bias. The evaluation results on this resource show that LLMs perform significantly worse than human in both directions. Furthermore, we apply the error grounding for filtering false alarmed errors, and achieve significant improvement in translation error detection.