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Nikolaos Pappas

19 accepted papers

2026

Capturing Gaze Shifts for Guidance: Cross-Modal Fusion Enhancement for VLM Hallucination Mitigation

ICML 2026poster

Vision language models (VLMs) often generate hallucination, i.e., content that cannot be substantiated by either textual or visual inputs. Prior work primarily attributes this to over-reliance on linguistic prior knowledge rather than visual inputs. Some methods attempt to mitigate hallucination by …

Cited by 0SourceScholar
2025

DeAL: Decoding-time Alignment for Large Language Models

ACL 2025long

Large Language Models (LLMs) are nowadays expected to generate content aligned with human preferences. Current work focuses on alignment at model training time, through techniques such as Reinforcement Learning with Human Feedback (RLHF). However, it is unclear if such methods are an effective choic…

Cited by 0SourcePDFScholar
2025

Rethinking LLM Uncertainty: A Multi-Agent Approach to Estimating Black-Box Model Uncertainty

EMNLP 2025

Quantifying uncertainty in black-box LLMs is vital for reliable responses and scalable oversight. Existing methods, which gauge a model’s uncertainty through evaluating self-consistency in responses to the target query, can be misleading: an LLM may confidently provide an incorrect answer to a targe

Cited by 0SourcePDFScholar
2025

Towards Long Context Hallucination Detection

NAACL 2025findings

Large Language Models (LLMs) have demonstrated remarkable performance across various tasks. However, they are prone to contextual hallucination, generating information that is either unsubstantiated or contradictory to the given context. Although many studies have investigated contextual hallucinati…

Cited by 2SourcePDFScholar
2025

Unraveling and Mitigating Safety Alignment Degradation of Vision-Language Models

ACL 2025finding

The safety alignment ability of Vision-Language Models (VLMs) is prone to be degraded by the integration of the vision module compared to its LLM backbone. We investigate this phenomenon, dubbed as “safety alignment degradation” in this paper, and show that the challenge arises from the representati…

Cited by 0SourcePDFScholar
2024

DEM: Distribution Edited Model for Training with Mixed Data Distributions

EMNLP 2024main

Training with mixed data distributions is a common and important part of creating multi-task and instruction-following models. The diversity of the data distributions and cost of joint training makes the optimization procedure extremely challenging. Data mixing methods partially address this problem…

2024

Eliciting Better Multilingual Structured Reasoning from LLMs through Code

ACL 2024long

The development of large language models (LLM) has shown progress on reasoning, though studies have largely considered either English or simple reasoning tasks. To address this, we introduce a multilingual structured reasoning and explanation dataset, termed xSTREET, that covers four tasks across si…

Cited by 8SourcePDFScholar
2024

MAGID: An Automated Pipeline for Generating Synthetic Multi-modal Datasets

NAACL 2024long

Development of multimodal interactive systems is hindered by the lack of rich, multimodal (text, images) conversational data, which is needed in large quantities for LLMs. Previous approaches augment textual dialogues with retrieved images, posing privacy, diversity, and quality constraints. In this…

2023

Measuring and Mitigating Constraint Violations of In-Context Learning for Utterance-to-API Semantic Parsing

EMNLP 2023long findings

In executable task-oriented semantic parsing, the system aims to translate users' utterances in natural language to machine-interpretable programs (API calls) that can be executed according to pre-defined API specifications. With the popularity of Large Language Models (LLMs), in-context learning of…

Cited by 0SourceScholar
2023

Pre-training Intent-Aware Encoders for Zero- and Few-Shot Intent Classification

EMNLP 2023long main

Intent classification (IC) plays an important role in task-oriented dialogue systems. However, IC models often generalize poorly when training without sufficient annotated examples for each user intent. We propose a novel pre-training method for text encoders that uses contrastive learning with inte…

Cited by 0SourcecodeScholar
2023

VCC: Scaling Transformers to 128K Tokens or More by Prioritizing Important Tokens

NeurIPS 2023poster

Transformers are central in modern natural language processing and computer vision applications. Despite recent works devoted to reducing the quadratic cost of such models with respect to sequence length, dealing with ultra long sequences (e.g., $>$16K tokens) remains challenging. Applications such…

2022

ABC: Attention with Bounded-memory Control

ACL 2022long

Transformer architectures have achieved state- of-the-art results on a variety of natural language processing (NLP) tasks. However, their attention mechanism comes with a quadratic complexity in sequence lengths, making the computational overhead prohibitive, especially for long sequences. Attention…

2022

Modeling Context With Linear Attention for Scalable Document-Level Translation

EMNLP 2022finding

Document-level machine translation leverages inter-sentence dependencies to produce more coherent and consistent translations. However, these models, predominantly based on transformers, are difficult to scale to long documents as their attention layers have quadratic complexity in the sequence leng…

2021

Deep Encoder, Shallow Decoder: Reevaluating Non-autoregressive Machine Translation

ICLR 2021poster

Much recent effort has been invested in non-autoregressive neural machine translation, which appears to be an efficient alternative to state-of-the-art autoregressive machine translation on modern GPUs. In contrast to the latter, where generation is sequential, the former allows generation to be pa…

2021

Finetuning Pretrained Transformers into RNNs

EMNLP 2021main

Transformers have outperformed recurrent neural networks (RNNs) in natural language generation. But this comes with a signifi- cant computational cost, as the attention mechanism’s complexity scales quadratically with sequence length. Efficient transformer variants have received increasing interest…

2021

Sentence Bottleneck Autoencoders from Transformer Language Models

EMNLP 2021main

Representation learning for text via pretraining a language model on a large corpus has become a standard starting point for building NLP systems. This approach stands in contrast to autoencoders, also trained on raw text, but with the objective of learning to encode each input as a vector that allo…

2020

Transformers are RNNs: Fast Autoregressive Transformers with Linear Attention

ICML 2020poster

Transformers achieve remarkable performance in several tasks but due to their quadratic complexity, with respect to the input’s length, they are prohibitively slow for very long sequences. To address this limitation, we express the self-attention as a linear dot-product of kernel feature maps and ma…