Meaning-infused grammar: Gradient Acceptability Shapes the Geometric Representations of Constructions in LLMs

The usage-based constructionist (UCx) approach posits that language comprises a network of learned form-meaning pairings (constructions) whose use is largely determined by their meanings or functions, requiring them to be graded and probabilistic. This study investigates whether the internal representations in Large Language Models (LLMs) reflect the proposed function-infused gradience. We analyze the neural representations of the English dative constructions (Double Object and Prepositional Object) in Pythia-$1.4$B, using a dataset of $5000$ sentence pairs systematically varied for human-rated preference strength. A macro-level geometric analysis finds that the separability between construction representations, as measured by Energy Distance or Jensen-Shannon Divergence, is systematically modulated by gradient preference strength. More prototypical exemplars of each construction occupy more distinct regions in the activation space of LLMs. These results provide strong evidence that LLMs learn rich, meaning-infused, graded representations of constructions and offer support for geometric measures of basic constructionist principles in LLMs.