Ryuichi Sumida

Author directory

2026

Memory systems for conversational LLMs are conventionally evaluated by direct, fact-seeking questions about prior dialogue (Direct QA): can the model recall fact X from a prior conversation? We tested whether higher Direct QA accuracy correlates with higher user satisfaction in a four-month deployment involving 40 users, 1,872 sessions, and seven memory conditions. Existing-benchmark Direct QA accuracy varies from 19.7% to 70.1% across the seven conditions, but satisfaction does not change. We hypothesize that existing benchmarks and user satisfaction measure different capabilities: benchmarks measure elicited retrieval—recall when explicitly asked—whereas natural conversation requires detecting relevance and appropriately integrating prior context into a response. To examine this distinction, we introduce MemUse, a benchmark of real user-cued memory moments drawn from the deployment and evaluated using integration-aware judgments of natural conversational responses. Holding the model and context fixed, the same system that scores 78.8% on Direct QA references only 7.9% of those facts in conversation, revealing a 71-point retrieval–integration gap. Within a small observational subset of naturally occurring memory moments, successful Natural Integration is positively associated with user satisfaction, whereas Direct QA performance is not. We release the deployment corpus and MemUse together with the associated judgments and scoring prompts.
The global deployment of Large Language Models (LLMs) underscores the urgent need to evaluate their cultural alignment. However, assessing genuine “cultural awareness” across modalities (text, vision, speech) and languages remains a significant challenge. To comprehensively investigate this domain, we propose MMAC, a systematic framework that encompasses a tri-modally aligned cultural benchmark creation pipeline and a five-dimensional evaluation protocol to assess cross-country awareness disparities, evaluate cross-lingual and cross-modal consistency, and verify cultural knowledge generalization and grounding validity. Given the prevailing Western cultural bias in current models, we focus on 8 Asian countries as our dataset foundation to more acutely reveal potential cultural deficiencies in LLMs. Our dataset, MMAC-bench, features 27,000 human-curated questions across 10 languages. Crucially, it is the first dataset aligned at the input level across text, image, and speech, enabling direct cross-modal transfer tests. Each question consists of multiple-choice options accompanied by open-ended generated explanations, where 79% require multi-step reasoning grounded in cultural context, moving beyond simple memorization. We probe the causes of modal divergence, offering insights into fostering culturally robust MLLMs.

2025

This study addresses the issue of what a Retrieval-Augmented Generation (RAG) chatbot should remember and what it should forget, based on findings from psychology. RAG retrieves relevant memories from past interactions to generate responses, and its effectiveness has been demonstrated. As conversations continue, however, the amount of stored memory keeps growing, which not only requires large storage capacity but also risks retaining unnecessary information, potentially reducing retrieval efficiency.To tackle this problem, we propose LUFY (Long-term Understanding and identiFYing key exchanges), a RAG chatbot that evaluates six distinct memory-related metrics derived from psychological models and real-world data. Instead of simply summing these metrics, it uses learned weights to account for the importance of each one. By using these weighted scores, the system can prioritize and retain relevant memories while gradually forgetting less important ones during both retrieval and memory management.To evaluate the effectiveness of LUFY in long-term conversations, we conducted experiments with human participants, who engaged in text-based conversations with three types of chatbots, each using different forgetting mechanisms, for at least two hours. The length of these conversations was more than 4.5 times longer than the longest conversations reported in previous studies. The results showed that prioritizing emotionally engaging memories while forgetting most of the conversation significantly enhanced user satisfaction.