Are reasoning paradigms scale-aware? A cross-paradigm verification of prompting, retrieval, and knowledge-graph scaffolding for small language models

Recent reasoning-enhancement paradigms, including chain-based prompting, retrieval-augmented generation, and graph-guided reasoning, have substantially improved the performance of large language models on question answering and knowledge-intensive tasks. However, whether these paradigms remain effective when transferred to small language models (SLMs) is still insufficiently understood. This question is particularly important for real-world deployments, where smaller models are often preferred due to resource constraints, latency requirements, and privacy considerations. In this paper, we conduct a scale-aware comparative study of reasoning enhancement for SLMs across three major families of methods: prompting-based reasoning, retrieval-based augmentation, and knowledge graph guided scaffolding. Using a unified experimental protocol, we evaluate representative paradigms on diverse question answering benchmarks and examine their behavior from three complementary perspectives: effectiveness, efficiency, and robustness. Our results show that reasoning-enhancement strategies are not universally transferable across model scales under the evaluated settings. In particular, chain-based prompting can become unstable on ultra-small models and is associated with longer, harder-to-control reasoning traces, while simply increasing unstructured retrieved context often yields limited gains at substantially higher token and latency costs. By contrast, graph-organized and graph-guided support is associated with more stable improvements in the evaluated multi-hop and knowledge-intensive settings, although its benefit remains dependent on graph quality, task structure, query-time cost, and the specific construction choices. These observations suggest that the success of reasoning enhancement depends not only on the method itself but also on the interaction with model scale and evidence organization. Beyond benchmarking, our study offers practical guidance for designing more inspectable, traceable, and resource-aware question answering systems, while pointing to structured evidence as a promising direction for adapting reasoning support to smaller foundation models under appropriate deployment conditions.