Siva Reddy

Biography

Siva Reddy is an assistant professor at the School of Computer Science and in the Department of Linguistics at McGill University. He completed a postdoc with the Stanford NLP Group in September 2019.

Reddy’s research goal is to enable machines with natural language understanding abilities in order to facilitate applications like question answering and conversational systems. His expertise includes building symbolic (linguistic and induced) and deep learning models for language.

Current Students

Vaibhav Adlakha

PhD - McGill University

Parishad BehnamGhader

Master's Research - McGill University

PhD - McGill University

Matteo Boglioni

Collaborating researcher - McGill University

Verna Dankers

Postdoctorate - University of Edinburgh

Jiaqi Deng

Collaborating researcher

Charbel El Feghali

Research Intern - McGill University

Desmond Elliott

Independent visiting researcher

Co-supervisor :

Yoshua Bengio

Jay Gala

Master's Research - McGill University

Co-supervisor :

Collaborating researcher

Collaborating Alumni

PhD - McGill University

Co-supervisor :

Timothy O'Donnell

Imene Kerboua

Collaborating researcher - INSA Lyon, France

PhD - McGill University

Principal supervisor :

Golnoosh Farnadi

Austin Kraft

PhD - McGill University

Co-supervisor :

Timothy O'Donnell

Benno Krojer

PhD - McGill University

Zichao Li

PhD - McGill University

Co-supervisor :

Jackie Cheung

Fengyuan Liu

Master's Research - McGill University

Co-supervisor :

Dzmitry Bahdanau

Xing Han Lu

PhD - McGill University

Master's Research - McGill University

Nicholas Meade

PhD - McGill University

Postdoctorate - McGill University

Marzia Nouri

Master's Research - McGill University

Arkil Patel

PhD - McGill University

Principal supervisor :

Collaborating researcher - N/A

Ben Saine

Research Intern - McGill University

Collaborating Alumni

Karolina Ewa Stańczak

Collaborating Alumni - McGill University

Ivan Titov

Collaborating researcher

Co-supervisor :

Yoshua Bengio

Ada Tur

Research Intern - McGill University

PhD - McGill University

Collaborating Alumni - McGill University

Donghao Zeng

Research Intern - McGill University

How Do We Explain AI and Ensure the Explanation Is True? Faithfulness Measurable Models Tell You How

Blog Posts

October 1, 2024

Andrea Madsen

Siva Reddy

Sarath Chandar

Read the article

Publications

When does word order matter and when doesn't it?

Xuanda Chen

Timothy John O'donnell

Language models (LMs) may appear insensitive to word order changes in natural language understanding (NLU) tasks. In this paper, we propose … (see more)that linguistic redundancy can explain this phenomenon, whereby word order and other linguistic cues such as case markers provide overlapping and thus redundant information. Our hypothesis is that models exhibit insensitivity to word order when the order provides redundant information, and the degree of insensitivity varies across tasks. We quantify how informative word order is using mutual information (MI) between unscrambled and scrambled sentences. Our results show the effect that the less informative word order is, the more consistent the model's predictions are between unscrambled and scrambled sentences. We also find that the effect varies across tasks: for some tasks, like SST-2, LMs' prediction is almost always consistent with the original one even if the Pointwise-MI (PMI) changes, while for others, like RTE, the consistency is near random when the PMI gets lower, i.e., word order is really important.

2024-02-28

ArXiv (preprint)

The Leukemoid Reaction in Severe Alcoholic Hepatitis: A Case Report

Sachin Agrawal

Sunil Kumar

Sourya Acharya

2024-02-10

Cureus (published)

Benchmarking Vision Language Models for Cultural Understanding

Sjoerd van Steenkiste

Lisa Anne Hendricks

Karolina Stanczak

Aishwarya Agrawal

Foundation models and vision-language pre-training have notably advanced Vision Language Models (VLMs), enabling multimodal processing of vi… (see more)sual and linguistic data. However, their performance has been typically assessed on general scene understanding - recognizing objects, attributes, and actions - rather than cultural comprehension. This study introduces CulturalVQA, a visual question-answering benchmark aimed at assessing VLM's geo-diverse cultural understanding. We curate a collection of 2,378 image-question pairs with 1-5 answers per question representing cultures from 11 countries across 5 continents. The questions probe understanding of various facets of culture such as clothing, food, drinks, rituals, and traditions. Benchmarking VLMs on CulturalVQA, including GPT-4V and Gemini, reveals disparity in their level of cultural understanding across regions, with strong cultural understanding capabilities for North America while significantly lower performance for Africa. We observe disparity in their performance across cultural facets too, with clothing, rituals, and traditions seeing higher performances than food and drink. These disparities help us identify areas where VLMs lack cultural understanding and demonstrate the potential of CulturalVQA as a comprehensive evaluation set for gauging VLM progress in understanding diverse cultures.

2023-12-31

EMNLP (published)

Evaluating Correctness and Faithfulness of Instruction-Following Models for Question Answering

Vaibhav Adlakha

Parishad BehnamGhader

Xing Han Lu

Nicholas Meade

Retriever-augmented instruction-following models are attractive alternatives to fine-tuned approaches for information-seeking tasks such as … (see more)question answering (QA). By simply prepending retrieved documents in its input along with an instruction, these models can be adapted to various information domains and tasks without additional fine-tuning. While the model responses tend to be natural and fluent, the additional verbosity makes traditional QA evaluation metrics such as exact match (EM) and F1 unreliable for accurately quantifying model performance. In this work, we investigate the performance of instruction-following models across three information-seeking QA tasks. We use both automatic and human evaluation to evaluate these models along two dimensions: 1) how well they satisfy the user's information need (correctness), and 2) whether they produce a response based on the provided knowledge (faithfulness). Guided by human evaluation and analysis, we highlight the shortcomings of traditional metrics for both correctness and faithfulness. We then propose simple token-overlap based and model-based metrics that reflect the true performance of these models. Our analysis reveals that instruction-following models are competitive, and sometimes even outperform fine-tuned models for correctness. However, these models struggle to stick to the provided knowledge and often hallucinate in their responses. We hope our work encourages a more holistic evaluation of instruction-following models for QA. Our code and data is available at https://github.com/McGill-NLP/instruct-qa

2023-12-31

Transactions of the Association for Computational Linguistics (published)

Reframing linguistic bootstrapping as joint inference using visually-grounded grammar induction models

Eva Portelance

Timothy J. O'Donnell

Semantic and syntactic bootstrapping posit that children use their prior knowledge of one linguistic domain, say syntactic relations, to hel… (see more)p later acquire another, such as the meanings of new words. Empirical results supporting both theories may tempt us to believe that these are different learning strategies, where one may precede the other. Here, we argue that they are instead both contingent on a more general learning strategy for language acquisition: joint learning. Using a series of neural visually-grounded grammar induction models, we demonstrate that both syntactic and semantic bootstrapping effects are strongest when syntax and semantics are learnt simultaneously. Joint learning results in better grammar induction, realistic lexical category learning, and better interpretations of novel sentence and verb meanings. Joint learning makes language acquisition easier for learners by mutually constraining the hypotheses spaces for both syntax and semantics. Studying the dynamics of joint inference over many input sources and modalities represents an important new direction for language modeling and learning research in both cognitive sciences and AI, as it may help us explain how language can be acquired in more constrained learning settings.

2023-12-31

arXiv (preprint)

Scope Ambiguities in Large Language Models

Gaurav Kamath

Sebastian Schuster

Sowmya Vajjala

Sentences containing multiple semantic operators with overlapping scope often create ambiguities in interpretation, known as scope ambiguiti… (see more)es. These ambiguities offer rich insights into the interaction between semantic structure and world knowledge in language processing. Despite this, there has been little research into how modern large language models treat them. In this paper, we investigate how different versions of certain autoregressive language models -- GPT-2, GPT-3/3.5, Llama 2 and GPT-4 -- treat scope ambiguous sentences, and compare this with human judgments. We introduce novel datasets that contain a joint total of almost 1,000 unique scope-ambiguous sentences, containing interactions between a range of semantic operators, and annotated for human judgments. Using these datasets, we find evidence that several models (i) are sensitive to the meaning ambiguity in these sentences, in a way that patterns well with human judgments, and (ii) can successfully identify human-preferred readings at a high level of accuracy (over 90% in some cases).

2023-12-31

Trans. Assoc. Comput. Linguistics (published)

Can Retriever-Augmented Language Models Reason? The Blame Game Between the Retriever and the Language Model

Parishad BehnamGhader

Santiago Miret

Augmenting pretrained language models with retrievers to select the supporting documents has shown promise in effectively solving common NLP… (see more) problems, including language modeling and question answering, in an interpretable way. In this paper, we first study the strengths and weaknesses of different retriever-augmented language models (REALM,

2023-11-30

Findings of the Association for Computational Linguistics: EMNLP 2023 (published)

Using In-Context Learning to Improve Dialogue Safety

Devamanyu Hazarika

Di Jin

Yang Liu

Dilek Hakkani-Tur

2023-10-06

EMNLP/2023/Conference (published)

Are Diffusion Models Vision-And-Language Reasoners?

Christopher Pal

Text-conditioned image generation models have recently shown immense qualitative success using denoising diffusion processes. However, unlik… (see more)e discriminative vision-and-language models, it is a non-trivial task to subject these diffusion-based generative models to automatic fine-grained quantitative evaluation of high-level phenomena such as compositionality. Towards this goal, we perform two innovations. First, we transform diffusion-based models (in our case, Stable Diffusion) for any image-text matching (ITM) task using a novel method called DiffusionITM. Second, we introduce the Generative-Discriminative Evaluation Benchmark (GDBench) benchmark with 7 complex vision-and-language tasks, bias evaluation and detailed analysis. We find that Stable Diffusion + DiffusionITM is competitive on many tasks and outperforms CLIP on compositional tasks like like CLEVR and Winoground. We further boost its compositional performance with a transfer setup by fine-tuning on MS-COCO while retaining generative capabilities. We also measure the stereotypical bias in diffusion models, and find that Stable Diffusion 2.1 is, for the most part, less biased than Stable Diffusion 1.5. Overall, our results point in an exciting direction bringing discriminative and generative model evaluation closer. We will release code and benchmark setup soon.

2023-09-20

NeurIPS.cc/2023/Conference (poster)

The Impact of Positional Encoding on Length Generalization in Transformers

Amirhossein Kazemnejad

Inkit Padhi

Karthikeyan Natesan Ramamurthy

Payel Das

Length generalization, the ability to generalize from small training context sizes to larger ones, is a critical challenge in the developmen… (see more)t of Transformer-based language models. Positional encoding (PE) has been identified as a major factor influencing length generalization, but the exact impact of different PE schemes on extrapolation in downstream tasks remains unclear. In this paper, we conduct a systematic empirical study comparing the length generalization performance of decoder-only Transformers with five different position encoding approaches including Absolute Position Embedding (APE), T5's Relative PE, ALiBi, and Rotary, in addition to Transformers without positional encoding (NoPE). Our evaluation encompasses a battery of reasoning and mathematical tasks. Our findings reveal that the most commonly used positional encoding methods, such as ALiBi, Rotary, and APE, are not well suited for length generalization in downstream tasks. More importantly, NoPE outperforms other explicit positional encoding methods while requiring no additional computation. We theoretically demonstrate that NoPE can represent both absolute and relative PEs, but when trained with SGD, it mostly resembles T5's relative PE attention patterns. Finally, we find that scratchpad is not always helpful to solve length generalization and its format highly impacts the model's performance. Overall, our work suggests that explicit position embeddings are not essential for decoder-only Transformers to generalize well to longer sequences.

2023-09-20

NeurIPS.cc/2023/Conference (poster)

In-Context Learning for Text Classification with Many Labels

Aristides Milios

Dzmitry Bahdanau

2023-09-18

ArXiv (preprint)