NDD-R1: Reinforcement Learning for Multimodal LLMs to Understand Communication in Non- and Minimally-Speaking Autistic Individuals

Siddhant Bikram Shah, Kristina T. Johnson


Abstract
Over 30% of autistic individuals are non- or minimally-speaking, relying on a complex, idiosyncratic repertoire of multimodal behaviors to communicate. Recognizing these intentional communicative acts in naturalistic environments remains a significant challenge for current multimodal large language models (MLLMs), which often struggle with the inference of subtle nonverbal cues in this domain. We introduce NDD-R1, a multi-stage reasoning framework that adapts a general-purpose MLLM for multi-view communication understanding for this population. Our approach employs a four-stage curriculum alternating between supervised finetuning and reinforcement learning (SFT1 → GRPO1 → SFT2 → GRPO2), integrating label-guided distillation, temperature-escalated self-distillation, and difficulty-tiered reward optimization. We evaluate NDD-R1 on an initial dataset collected through the Rapid Online Sample of Communication (ROSCO) protocol, comprising 2,582 caregiver-annotated multi-view videos of 27 non- and minimally-speaking autistic individuals. NDD-R1 outperforms baselines on action and joint classification tasks, achieving competitive function classification performance relative to Gemini, exhibiting strong multi-view scaling and generalization across unseen sessions. Our code is available at https://github.com/SiddhantBikram/NDD-R1.
Anthology ID:
2026.findings-emnlp.1630
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
34681–34697
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1630/
DOI:
10.18653/2026.findings-emnlp.1630
Bibkey:
Cite (ACL):
Siddhant Bikram Shah and Kristina T. Johnson. 2026. NDD-R1: Reinforcement Learning for Multimodal LLMs to Understand Communication in Non- and Minimally-Speaking Autistic Individuals. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 34681–34697, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
NDD-R1: Reinforcement Learning for Multimodal LLMs to Understand Communication in Non- and Minimally-Speaking Autistic Individuals (Shah & Johnson, Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.1630.pdf