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Why do LLMs handle causal reasoning better than temporal reasoning?

Exploring whether language models perform asymmetrically on different discourse relations and what training data patterns might explain the gap between causal and temporal reasoning abilities.

Synthesis note · 2026-02-21 · sourced from Discourses

From the same discourse relations study: ChatGPT shows strong performance on causal relations — outperforming fine-tuned RoBERTa on two out of three benchmarks — while struggling with temporal order between events.

The most plausible explanation offered by the researchers: causal reasoning difficulty in temporal tasks "could be attributed to inadequate human feedback on this feature during the model's training process" — but more fundamentally, causal language is pervasive and explicitly marked in text. Explanations, arguments, news articles, scientific writing — all of these use causal connectives ("because," "therefore," "leads to," "causes") extensively and consistently.

Temporal order, by contrast, is often implicit. We say "she went to the store and bought milk" without specifying whether the events are sequential, simultaneous, or ordered in some other way. The ordering must be inferred from context, world knowledge, and linguistic cues that are less reliable than causal connectives.

The result is a capability asymmetry that tracks training data distribution: what's frequently and explicitly marked in text, LLMs learn to handle well. What's frequently implicit, they struggle with.

This is a generalizable prediction: wherever human language uses explicit, consistent surface markers, LLMs will perform better than where the same information is conveyed implicitly. Causal > temporal is one instance of this pattern. The same logic should apply to other discourse relations, pragmatic inferences, and any semantic content that is typically left implicit in language.

Shared biases, not just relative performance: The picture becomes more complex when comparing LLM causal reasoning not just against benchmarks but against human performance on the same tasks. "Do LLMs Reason Causally Like Us?" finds that on collider network reasoning (C1 → E ← C2), LLMs exhibit the same biases as humans: Markov violations (treating independent causes as positively correlated) and weak explaining away (the effect of observing one cause on reducing the probability of the other is weaker than normatively warranted). LLMs are not categorically worse at causal reasoning — they err in the same direction, likely because training data was produced by humans with these same biases. See Do large language models make the same causal reasoning mistakes as humans?.

Inquiring lines that read this note 59

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Should AI communication design follow human conversation norms or develop distinct machine-specific principles? What mechanisms preserve shared understanding in evolving conversations? What explains language models' asymmetric difficulty with implicit versus explicit linguistic relations? What enables genuine semantic understanding in language models? Do language models develop actual world models or merely task heuristics? Do language models reason through causal mechanisms or semantic associations? Do language models learn genuine understanding or just surface patterns? Why do some clarifying approaches produce understanding while others just satisfy? How should retrieval systems handle complex multi-step reasoning? Is language model reasoning authentic and what causes models to reason? Can AI systems distinguish genuine empathy from simulated emotion? What compositional reasoning failures limit large language models despite scale? Do reasoning traces faithfully reflect actual model reasoning? Does encoded knowledge in language models actually influence their outputs? How effectively can language models perform reasoning, especially combined with symbolic methods? How do recommenders balance exploiting fresh signals against maintaining preference stability? Why do stronger reasoning capabilities create tradeoffs with instruction following? What reasoning architectures enable models to solve complex problems efficiently? Can models improve accuracy without degrading reasoning quality? How should systems decide whether to retrieve or reason alone? Can inference-time compute effectively substitute for model scale? How does decomposing tasks improve reasoning and prevent failure propagation? Why do token-level mechanisms matter for learning to reason? What structural distinctions matter in reasoning and argumentation? How does reasoning length affect model performance across different tasks? What training dynamics and scale trigger emergence of reasoning capabilities?

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Original note title

causal reasoning is stronger than temporal reasoning in llms because causal patterns dominate training data