PuMer: Pruning and Merging Tokens for Efficient Vision Language Models
On the map: Multimodal LLMs / vision-language models → Visual token pruning and efficiency
Abstract (arXiv)
Large-scale vision language (VL) models use Transformers to perform cross-modal interactions between the input text and image. These cross-modal interactions are computationally expensive and memory-intensive due to the quadratic complexity of processing the input image and text. We present PuMer: a token reduction framework that uses text-informed Pruning and modality-aware Merging strategies to progressively reduce the tokens of input image and text, improving model inference speed and reducing memory footprint. PuMer learns to keep salient image tokens related to the input text and merges similar textual and visual tokens by adding lightweight token reducer modules at several cross-modal layers in the VL model. Training PuMer is mostly the same as finetuning the original VL model but faster. Our evaluation for two vision language models on four downstream VL tasks shows PuMer increases inference throughput by up to 2x and reduces memory footprint by over 50% while incurring less than a 1% accuracy drop.
Key facts. Cited by 53 papers in the map (data through 14 Oct 2026). Placed in Visual token pruning and efficiency, one of 16 directions in Multimodal LLMs / vision-language models. Builds on 33 of its 45 references that are in the map. First posted on arXiv 27 May 2023.
Builds on
33 of 45 references.
References · 33
- 2017Attention Is All You Needcited by 60,361
- 2018BERT: Pre-training of Deep Bidirectional Transformers for Language Understandingcited by 40,399
- 2021Learning Transferable Visual Models From Natural Language Supervisioncited by 33,744
- 2020An Image is Worth 16x16 Words: Transformers for Image Recognition at Scalecited by 30,186
- 2014Microsoft COCO: Common Objects in Contextcited by 17,608
- 2019RoBERTa: A Robustly Optimized BERT Pretraining Approachcited by 13,372
- 2015Distilling the Knowledge in a Neural Networkcited by 10,324
- 2016Making the V in VQA Matter: Elevating the Role of Image Understanding in Visual Question Answeringcited by 2,516
- 2015A large annotated corpus for learning natural language inferencecited by 1,847
- 2021Align before Fuse: Vision and Language Representation Learning with Momentum Distillationcited by 1,619
- 2015Flickr30k Entities: Collecting Region-to-Phrase Correspondences for Richer Image-to-Sentence Modelscited by 1,362
- 2021ViLT: Vision-and-Language Transformer Without Convolution or Region Supervisioncited by 1,230
21 more
- 2022Token Merging: Your ViT But Fastercited by 1,021
- 2021DynamicViT: Efficient Vision Transformers with Dynamic Token Sparsificationcited by 864
- 2022OFA: Unifying Architectures, Tasks, and Modalities Through a Simple Sequence-to-Sequence Learning Frameworkcited by 745
- 2021SimVLM: Simple Visual Language Model Pretraining with Weak Supervisioncited by 647
- 2022GroupViT: Semantic Segmentation Emerges from Text Supervisioncited by 531
- 2021LeViT: a Vision Transformer in ConvNet's Clothing for Faster Inferencecited by 475
- 2018A Corpus for Reasoning About Natural Language Grounded in Photographscited by 459
- 2021AdaViT: Adaptive Tokens for Efficient Vision Transformercited by 362
- 2020BERT Loses Patience: Fast and Robust Inference with Early Exitcited by 273
- 2021An Empirical Study of Training End-to-End Vision-and-Language Transformerscited by 271
- 2021Multi-Grained Vision Language Pre-Training: Aligning Texts with Visual Conceptscited by 256
- 2020FastBERT: a Self-distilling BERT with Adaptive Inference Timecited by 226
- 2021Block Pruning For Faster Transformerscited by 177
- 2021TokenLearner: What Can 8 Learned Tokens Do for Images and Videos?cited by 127
- 2020The Right Tool for the Job: Matching Model and Instance Complexitiescited by 126
- 2021Compressing Visual-linguistic Model via Knowledge Distillationcited by 86
- 2022Efficient Transformers with Dynamic Token Poolingcited by 76
- 2021Token Pooling in Vision Transformerscited by 69
- 2020MiniVLM: A Smaller and Faster Vision-Language Modelcited by 51
- 2021A Unified Pruning Framework for Vision Transformerscited by 40
- 2018Visual Entailment Task for Visually-Grounded Language Learningcited by 36
Built on by
Citing papers per year: 2023: 1; 2024: 12; 2025: 27; 2026: 13.
53 papers.
Sort:
By area:
- 2024PyramidDrop: Accelerating Your Large Vision-Language Models via Pyramid Visual Redundancy Reductioncited by 294
- 2024Mobile Edge Intelligence for Large Language Models: A Contemporary Surveycited by 128
- 2025FastVGGT: Training-Free Acceleration of Visual Geometry Transformercited by 98
- 2023MobileCLIP: Fast Image-Text Models through Multi-Modal Reinforced Trainingcited by 96
- 2024Self-Introspective Decoding: Alleviating Hallucinations for Large Vision-Language Modelscited by 94
- 2025VLA-Cache: Efficient Vision-Language-Action Manipulation via Adaptive Token Cachingcited by 86
- 2025VL-JEPA: Joint Embedding Predictive Architecture for Vision-languagecited by 68
- 2025Token Reduction Should Go Beyond Efficiency in Generative Models -- From Vision, Language to Multimodalitycited by 50
- 2024SafeWatch: An Efficient Safety-Policy Following Video Guardrail Model with Transparent Explanationscited by 38
- 2025What Kind of Visual Tokens Do We Need? Training-free Visual Token Pruning for Multi-modal Large Language Models from the Perspective of Graphcited by 36
- 2024Accelerating Transformers with Spectrum-Preserving Token Mergingcited by 35
- 2025Shifting AI Efficiency From Model-Centric to Data-Centric Compressioncited by 29
38 more
- 2024ALGM: Adaptive Local-then-Global Token Merging for Efficient Semantic Segmentation with Plain Vision Transformerscited by 28
- 2025A Survey of Token Compression for Efficient Multimodal Large Language Modelscited by 25
- 2025MobileCLIP2: Improving Multi-Modal Reinforced Trainingcited by 21
- 2025Hybrid Token Compression for Vision-Language Modelscited by 20
- 2024Efficient Vision-Language Models by Summarizing Visual Tokens into Compact Registerscited by 19
- 2025LiteVGGT: Boosting Vanilla VGGT via Geometry-aware Cached Token Mergingcited by 17
- 2024Rethinking Token Reduction for State Space Modelscited by 15
- 2025Evict3R: Training-Free Token Eviction for Memory-Bounded Streaming Visual Geometry Transformerscited by 14
- 2025Accelerating Vision Transformers with Adaptive Patch Sizescited by 13
- 2025MergeVQ: A Unified Framework for Visual Generation and Representation with Disentangled Token Merging and Quantizationcited by 12
- 2026The Model Knows Which Tokens Matter: Automatic Token Selection via Noise Gatingcited by 11
- 2025Co-Me: Confidence-Guided Token Merging for Visual Geometric Transformerscited by 10
- 2024PaPr: Training-Free One-Step Patch Pruning with Lightweight ConvNets for Faster Inferencecited by 9
- 2025Grounding-Aware Token Pruning: Recovering from Drastic Performance Drops in Visual Grounding Caused by Pruningcited by 9
- 2026Attend Before Attention: Efficient and Scalable Video Understanding via Autoregressive Gazingcited by 9
- 2024Famba-V: Fast Vision Mamba with Cross-Layer Token Fusioncited by 8
- 2025A Survey on Mamba Architecture for Vision Applicationscited by 8
- 2025One Trajectory, One Token: Grounded Video Tokenization via Panoptic Sub-object Trajectorycited by 7
- 2024Deploying Foundation Model Powered Agent Services: A Surveycited by 4
- 2025Efficient Token Compression for Vision Transformer with Spatial Information Preservedcited by 4
- 2025RedVTP: Training-Free Acceleration of Diffusion Vision-Language Models Inference via Masked Token-Guided Visual Token Pruningcited by 4
- 2024Visual-Word Tokenizer: Beyond Fixed Sets of Tokens in Vision Transformerscited by 2
- 2025STAR: Stage-Wise Attention-Guided Token Reduction for Efficient Large Vision-Language Models Inferencecited by 2
- 2025QLIP: A Dynamic Quadtree Vision Prior Enhances MLLM Performance Without Retrainingcited by 2
- 2025Video, How Do Your Tokens Merge?cited by 2
- 2026Temporal Aware Pruning for Efficient Diffusion-based Video Generationcited by 2
- 2025NEURAL: Attention-Guided Pruning for Unified Multimodal Resource-Constrained Clinical Evaluationcited by 1
- 2025AttAnchor: Guiding Cross-Modal Token Alignment in VLMs with Attention Anchorscited by 1
- 2025AdaTok: Adaptive Token Compression with Object-Aware Representations for Efficient Multimodal LLMscited by 1
- 2026Learning to Accelerate Vision-Language-Action Models through Adaptive Visual Token Cachingcited by 1
- 2026ASAP: Attention-Shift-Aware Pruning for Efficient LVLM Inferencecited by 1
- 2026LookWhen? Fast Video Recognition by Learning When, Where, and What to Computecited by 1
- 2026OTT-Vid: Optimal Transport Temporal Token Compression for Video Large Language Modelscited by 1
- 2026Fast Enough to Act: Spatio-Temporal Visual Token Merging for Low-Latency Robotic VLMs and VLAscited by 1
- 2025Dynamic Pyramid Network for Efficient Multimodal Large Language Modelcited by 0
- 2025Improving MLLM Training Efficiency via Stage-Aware Sparsitycited by 0
- 2026Taking Shortcuts for Categorical VQA Using Super Neuronscited by 0
- 2026Towards Efficient Large Vision-Language Models: A Comprehensive Survey on Inference Strategiescited by 0
50 most cited of 53 All 53 (JSON)
- 2026When Text Matters: Design Principles for Visual Token Pruning in Vision-Language Model28 Sep 2026
- 2026BrainFocus: EEG-Guided ROI Selection for Efficient Vision-Language Models15 Sep 2026
- 2026StepPrune: Adaptive Sequential Visual Token Selection across Multimodal Large Language Models12 Sep 2026
- 2026Fast Enough to Act: Spatio-Temporal Visual Token Merging for Low-Latency Robotic VLMs and VLAs28 Jun 2026
- 2026Temporal Aware Pruning for Efficient Diffusion-based Video Generation18 May 2026
- 2026OTT-Vid: Optimal Transport Temporal Token Compression for Video Large Language Models12 May 2026
- 2026LookWhen? Fast Video Recognition by Learning When, Where, and What to Compute7 May 2026
- 2026Towards Efficient Large Vision-Language Models: A Comprehensive Survey on Inference Strategies30 Mar 2026
- 2026ASAP: Attention-Shift-Aware Pruning for Efficient LVLM Inference15 Mar 2026
- 2026Attend Before Attention: Efficient and Scalable Video Understanding via Autoregressive Gazing12 Mar 2026
- 2026Taking Shortcuts for Categorical VQA Using Super Neurons11 Mar 2026
- 2026The Model Knows Which Tokens Matter: Automatic Token Selection via Noise Gating7 Mar 2026
38 more
- 2026Learning to Accelerate Vision-Language-Action Models through Adaptive Visual Token Caching31 Jan 2026
- 2025VL-JEPA: Joint Embedding Predictive Architecture for Vision-language11 Dec 2025
- 2025Hybrid Token Compression for Vision-Language Models9 Dec 2025
- 2025LiteVGGT: Boosting Vanilla VGGT via Geometry-aware Cached Token Merging4 Dec 2025
- 2025Co-Me: Confidence-Guided Token Merging for Visual Geometric Transformers18 Nov 2025
- 2025AdaTok: Adaptive Token Compression with Object-Aware Representations for Efficient Multimodal LLMs18 Nov 2025
- 2025RedVTP: Training-Free Acceleration of Diffusion Vision-Language Models Inference via Masked Token-Guided Visual Token Pruning16 Nov 2025
- 2025Accelerating Vision Transformers with Adaptive Patch Sizes20 Oct 2025
- 2025AttAnchor: Guiding Cross-Modal Token Alignment in VLMs with Attention Anchors27 Sep 2025
- 2025Evict3R: Training-Free Token Eviction for Memory-Bounded Streaming Visual Geometry Transformers22 Sep 2025
- 2025Improving MLLM Training Efficiency via Stage-Aware Sparsity16 Sep 2025
- 2025FastVGGT: Training-Free Acceleration of Visual Geometry Transformer2 Sep 2025
- 2025MobileCLIP2: Improving Multi-Modal Reinforced Training28 Aug 2025
- 2025NEURAL: Attention-Guided Pruning for Unified Multimodal Resource-Constrained Clinical Evaluation13 Aug 2025
- 2025A Survey of Token Compression for Efficient Multimodal Large Language Models27 Jul 2025
- 2025Grounding-Aware Token Pruning: Recovering from Drastic Performance Drops in Visual Grounding Caused by Pruning27 Jun 2025
- 2025Video, How Do Your Tokens Merge?4 Jun 2025
- 2025One Trajectory, One Token: Grounded Video Tokenization via Panoptic Sub-object Trajectory29 May 2025
- 2025QLIP: A Dynamic Quadtree Vision Prior Enhances MLLM Performance Without Retraining29 May 2025
- 2025Shifting AI Efficiency From Model-Centric to Data-Centric Compression25 May 2025
- 2025Token Reduction Should Go Beyond Efficiency in Generative Models -- From Vision, Language to Multimodality23 May 2025
- 2025STAR: Stage-Wise Attention-Guided Token Reduction for Efficient Large Vision-Language Models Inference18 May 2025
- 2025MergeVQ: A Unified Framework for Visual Generation and Representation with Disentangled Token Merging and Quantization1 Apr 2025
- 2025Efficient Token Compression for Vision Transformer with Spatial Information Preserved30 Mar 2025
- 2025Dynamic Pyramid Network for Efficient Multimodal Large Language Model26 Mar 2025
- 2025A Survey on Mamba Architecture for Vision Applications11 Feb 2025
- 2025VLA-Cache: Efficient Vision-Language-Action Manipulation via Adaptive Token Caching4 Feb 2025
- 2025What Kind of Visual Tokens Do We Need? Training-free Visual Token Pruning for Multi-modal Large Language Models from the Perspective of Graph4 Jan 2025
- 2024Deploying Foundation Model Powered Agent Services: A Survey18 Dec 2024
- 2024SafeWatch: An Efficient Safety-Policy Following Video Guardrail Model with Transparent Explanations9 Dec 2024
- 2024Visual-Word Tokenizer: Beyond Fixed Sets of Tokens in Vision Transformers23 Nov 2024
- 2024PyramidDrop: Accelerating Your Large Vision-Language Models via Pyramid Visual Redundancy Reduction22 Oct 2024
- 2024Efficient Vision-Language Models by Summarizing Visual Tokens into Compact Registers17 Oct 2024
- 2024Rethinking Token Reduction for State Space Models16 Oct 2024
- 2024Famba-V: Fast Vision Mamba with Cross-Layer Token Fusion15 Sep 2024
- 2024Self-Introspective Decoding: Alleviating Hallucinations for Large Vision-Language Models4 Aug 2024
- 2024Mobile Edge Intelligence for Large Language Models: A Contemporary Survey9 Jul 2024
- 2024ALGM: Adaptive Local-then-Global Token Merging for Efficient Semantic Segmentation with Plain Vision Transformers14 Jun 2024
50 newest of 53 All 53 (JSON)
- 2024PyramidDrop: Accelerating Your Large Vision-Language Models via Pyramid Visual Redundancy Reductioncited by 294
- 2024Self-Introspective Decoding: Alleviating Hallucinations for Large Vision-Language Modelscited by 94
- 2025VL-JEPA: Joint Embedding Predictive Architecture for Vision-languagecited by 68
- 2025What Kind of Visual Tokens Do We Need? Training-free Visual Token Pruning for Multi-modal Large Language Models from the Perspective of Graphcited by 36
- 2025Shifting AI Efficiency From Model-Centric to Data-Centric Compressioncited by 29
- 2025A Survey of Token Compression for Efficient Multimodal Large Language Modelscited by 25
- 2025Hybrid Token Compression for Vision-Language Modelscited by 20
- 2024Efficient Vision-Language Models by Summarizing Visual Tokens into Compact Registerscited by 19
- 2026The Model Knows Which Tokens Matter: Automatic Token Selection via Noise Gatingcited by 11
- 2025Grounding-Aware Token Pruning: Recovering from Drastic Performance Drops in Visual Grounding Caused by Pruningcited by 9
- 2026Attend Before Attention: Efficient and Scalable Video Understanding via Autoregressive Gazingcited by 9
- 2025STAR: Stage-Wise Attention-Guided Token Reduction for Efficient Large Vision-Language Models Inferencecited by 2
12 most cited of 22 All 22 (JSON)
- 2026When Text Matters: Design Principles for Visual Token Pruning in Vision-Language Model28 Sep 2026
- 2026BrainFocus: EEG-Guided ROI Selection for Efficient Vision-Language Models15 Sep 2026
- 2026StepPrune: Adaptive Sequential Visual Token Selection across Multimodal Large Language Models12 Sep 2026
- 2026Fast Enough to Act: Spatio-Temporal Visual Token Merging for Low-Latency Robotic VLMs and VLAs28 Jun 2026
- 2026ASAP: Attention-Shift-Aware Pruning for Efficient LVLM Inference15 Mar 2026
- 2026Attend Before Attention: Efficient and Scalable Video Understanding via Autoregressive Gazing12 Mar 2026
- 2026Taking Shortcuts for Categorical VQA Using Super Neurons11 Mar 2026
- 2026The Model Knows Which Tokens Matter: Automatic Token Selection via Noise Gating7 Mar 2026
- 2025VL-JEPA: Joint Embedding Predictive Architecture for Vision-language11 Dec 2025
- 2025Hybrid Token Compression for Vision-Language Models9 Dec 2025
- 2025AdaTok: Adaptive Token Compression with Object-Aware Representations for Efficient Multimodal LLMs18 Nov 2025
- 2025Improving MLLM Training Efficiency via Stage-Aware Sparsity16 Sep 2025
12 newest of 22 All 22 (JSON)
- 2025FastVGGT: Training-Free Acceleration of Visual Geometry Transformercited by 98
- 2025Token Reduction Should Go Beyond Efficiency in Generative Models -- From Vision, Language to Multimodalitycited by 50
- 2024Accelerating Transformers with Spectrum-Preserving Token Mergingcited by 35
- 2024ALGM: Adaptive Local-then-Global Token Merging for Efficient Semantic Segmentation with Plain Vision Transformerscited by 28
- 2025LiteVGGT: Boosting Vanilla VGGT via Geometry-aware Cached Token Mergingcited by 17
- 2025Evict3R: Training-Free Token Eviction for Memory-Bounded Streaming Visual Geometry Transformerscited by 14
- 2025MergeVQ: A Unified Framework for Visual Generation and Representation with Disentangled Token Merging and Quantizationcited by 12
- 2025Co-Me: Confidence-Guided Token Merging for Visual Geometric Transformerscited by 10
- 2025Efficient Token Compression for Vision Transformer with Spatial Information Preservedcited by 4
- 2026OTT-Vid: Optimal Transport Temporal Token Compression for Video Large Language Modelscited by 1
- 2026OTT-Vid: Optimal Transport Temporal Token Compression for Video Large Language Models12 May 2026
- 2025LiteVGGT: Boosting Vanilla VGGT via Geometry-aware Cached Token Merging4 Dec 2025
- 2025Co-Me: Confidence-Guided Token Merging for Visual Geometric Transformers18 Nov 2025
- 2025Evict3R: Training-Free Token Eviction for Memory-Bounded Streaming Visual Geometry Transformers22 Sep 2025
- 2025FastVGGT: Training-Free Acceleration of Visual Geometry Transformer2 Sep 2025
- 2025Token Reduction Should Go Beyond Efficiency in Generative Models -- From Vision, Language to Multimodality23 May 2025
- 2025MergeVQ: A Unified Framework for Visual Generation and Representation with Disentangled Token Merging and Quantization1 Apr 2025
- 2025Efficient Token Compression for Vision Transformer with Spatial Information Preserved30 Mar 2025
- 2024ALGM: Adaptive Local-then-Global Token Merging for Efficient Semantic Segmentation with Plain Vision Transformers14 Jun 2024
- 2024Accelerating Transformers with Spectrum-Preserving Token Merging25 May 2024
- 2025VLA-Cache: Efficient Vision-Language-Action Manipulation via Adaptive Token Cachingcited by 86
- 2024Rethinking Token Reduction for State Space Modelscited by 15
- 2025RedVTP: Training-Free Acceleration of Diffusion Vision-Language Models Inference via Masked Token-Guided Visual Token Pruningcited by 4
- 2026Towards Efficient Large Vision-Language Models: A Comprehensive Survey on Inference Strategiescited by 0
- 2026Towards Efficient Large Vision-Language Models: A Comprehensive Survey on Inference Strategies30 Mar 2026
- 2025RedVTP: Training-Free Acceleration of Diffusion Vision-Language Models Inference via Masked Token-Guided Visual Token Pruning16 Nov 2025
- 2025VLA-Cache: Efficient Vision-Language-Action Manipulation via Adaptive Token Caching4 Feb 2025
- 2024Rethinking Token Reduction for State Space Models16 Oct 2024
- 2024Famba-V: Fast Vision Mamba with Cross-Layer Token Fusioncited by 8
- 2025A Survey on Mamba Architecture for Vision Applicationscited by 8
- 2025A Survey on Mamba Architecture for Vision Applications11 Feb 2025
- 2024Famba-V: Fast Vision Mamba with Cross-Layer Token Fusion15 Sep 2024
- 2024Deploying Foundation Model Powered Agent Services: A Survey18 Dec 2024
- 2025MobileCLIP2: Improving Multi-Modal Reinforced Trainingcited by 21
- 2025MobileCLIP2: Improving Multi-Modal Reinforced Training28 Aug 2025
- 2024Mobile Edge Intelligence for Large Language Models: A Contemporary Surveycited by 128
- 2023MobileCLIP: Fast Image-Text Models through Multi-Modal Reinforced Trainingcited by 96
- 2025Accelerating Vision Transformers with Adaptive Patch Sizescited by 13
- 2024PaPr: Training-Free One-Step Patch Pruning with Lightweight ConvNets for Faster Inferencecited by 9
- 2025One Trajectory, One Token: Grounded Video Tokenization via Panoptic Sub-object Trajectorycited by 7
- 2024Visual-Word Tokenizer: Beyond Fixed Sets of Tokens in Vision Transformerscited by 2
- 2025Video, How Do Your Tokens Merge?cited by 2
- 2025NEURAL: Attention-Guided Pruning for Unified Multimodal Resource-Constrained Clinical Evaluationcited by 1
- 2025AttAnchor: Guiding Cross-Modal Token Alignment in VLMs with Attention Anchorscited by 1
- 2026LookWhen? Fast Video Recognition by Learning When, Where, and What to Computecited by 1
- 2026LookWhen? Fast Video Recognition by Learning When, Where, and What to Compute7 May 2026
- 2025Accelerating Vision Transformers with Adaptive Patch Sizes20 Oct 2025
- 2025AttAnchor: Guiding Cross-Modal Token Alignment in VLMs with Attention Anchors27 Sep 2025
- 2025NEURAL: Attention-Guided Pruning for Unified Multimodal Resource-Constrained Clinical Evaluation13 Aug 2025
- 2025Video, How Do Your Tokens Merge?4 Jun 2025
- 2025One Trajectory, One Token: Grounded Video Tokenization via Panoptic Sub-object Trajectory29 May 2025
- 2024Visual-Word Tokenizer: Beyond Fixed Sets of Tokens in Vision Transformers23 Nov 2024
- 2024Mobile Edge Intelligence for Large Language Models: A Contemporary Survey9 Jul 2024
- 2024PaPr: Training-Free One-Step Patch Pruning with Lightweight ConvNets for Faster Inference24 Mar 2024
- 2023MobileCLIP: Fast Image-Text Models through Multi-Modal Reinforced Training28 Nov 2023
Similar, not cited
Close in wording, no citation either way
- 2026SwiftVLM: Efficient Vision-Language Model Inference via Cross-Layer Token Bypass
- 2026From Patching to Pruning Visual Computation in Vision Language Models
- 2025LVPruning: An Effective yet Simple Language-Guided Vision Token Pruning Approach for Multi-modal Large Language Models
- 2025Balanced Token Pruning: Accelerating Vision Language Models Beyond Local Optimization
- 2025Object-Centric Vision Token Pruning for Vision Language Models
- 2025Efficient Vision-Language Reasoning via Adaptive Token Pruning
- 2022EfficientVLM: Fast and Accurate Vision-Language Models via Knowledge Distillation and Modal-adaptive Pruning
- 2025VScan: Rethinking Visual Token Reduction for Efficient Large Vision-Language Models