From Tokens to Thoughts

LLMs do form broad conceptual categories that align well with human groupings. Adjusted Mutual Information scores show LLM clusters consistently outperform random baselines, with even small encoder models like BERT matching or beating larger decoder-only models on this alignment task.

However, LLMs struggle with fine-grained semantics. When tested on their ability to mirror human notions of item typicality (e.g., robin as a more typical bird than penguin), correlations between LLM embedding similarity and human ratings were weak and inconsistent. Most models failed to capture graded prototype structures evident in human cognition.

Using their unified loss function L (balancing information complexity and semantic distortion), the authors find that LLMs produce statistically efficient clusters with lower entropy and distortion, while human conceptual clusters are less compact but preserve richer nuance. This suggests LLMs over-optimize for compression at the expense of meaning, unlike humans, who tolerate inefficiency to retain adaptive, flexible structure.

The paper concludes that while LLMs can mimic surface-level categorization, they diverge fundamentally in how they represent meaning, highlighting a core gap between artificial and human semantic systems and offering a quantitative tool for improving human-aligned conceptual representations.