Papers by Tiago Pimentel
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| Challenge: | Language modeling is a core task in natural language processing. |
| Approach: | They propose to characterize leakage onto the set of infinite sequences by a measure-theoretic approach. |
| Outcome: | The proposed language model families are tight, meaning they will not leak . the proposed language models are based on the 'sequence leakage' hypothesis . |
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| Challenge: | Existing studies have found that higher quality language models provide more powerful predictors of human reading behavior, but empirical support for the QP hypothesis is mixed. |
| Approach: | They propose to test the quality–power hypothesis by using surprisal language models to test their ability to predict eye tracking data. |
| Outcome: | The proposed model is based on a set of language models with a 'quality-power' hypothesis. |
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| Challenge: | a novel model for estimating the unigram distribution is proposed for a language . the model is based on the word type and word type distributions, but does not consider contextual information. |
| Approach: | They propose a neuralization of Goldwater's (2011) model for estimating the unigram distribution in a language. |
| Outcome: | The proposed model outperforms character-level models in estimating the unigram distribution in a language. |
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| Challenge: | a recent study suggests that mode-seeking decoding methods produce unnatural language . a higher probability text is perceived as more human-like, but this is not the case with stochastic decoding . |
| Approach: | They propose to explain why higher-probability text is perceived as more human-like . they argue that human-type language should contain an amount of information close to entropy . |
| Outcome: | The proposed model produces lower-probability text, which is perceived as more human-like . elucidation of this hypothesis supports the hypothesis . |
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| Challenge: | Tokenisation is a core part of language models but can lead to less efficient training because it removes character-level information. |
| Approach: | They propose to use a tokenisation method to split a character sequence into subwords which are assigned random indices before being served to the LM. |
| Outcome: | The proposed model can generalise across duplicated subwords, but this incurs extra cost and is less data efficient. |
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| Challenge: | researchers train supervised models to extract linguistic structure from output of another model . supervised model can be used to perform tasks such as part-of-speech tags or dependency trees . |
| Approach: | They compare a structural probe to a more traditional parser with a lightweight parameterisation. |
| Outcome: | The structural probe outperforms a traditional parser on seven of nine languages . the researchers found that the model outperformed the parsers by 11.1 points . |
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| Challenge: | Scholars of human development have long debated whether these phenomena are predetermined by innately encoded developmental changes in the maturing brain or natural consequences of increased experience. |
| Approach: | They use language models to test whether CP effects are peculiar to humans . they find that LMs do not show CP when L2 exposure is delayed . scholars have long debated whether innate maturation changes predetermine CP . |
| Outcome: | The proposed model does not show CP effects when the age of exposure of L2 is delayed. |
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| Challenge: | Pre-trained language models can be used to perform a wide array of NLP tasks, but their encoding is still a mystery. |
| Approach: | They propose a usage-based probing setup to find an encoding that the model actually uses, and propose 'a use-based approach' they propose to use a behavioral task to remove the linguistic property, and to identify which encodes are used to transfer information from a noun to its head verb. |
| Outcome: | The proposed encodings are based on a behavioral task which cannot be solved without the linguistic property. |
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| Challenge: | a large body of work has examined the training dynamics of language models. |
| Approach: | They investigate the convergence of language models (LMs) trained under different random seeds . they find that larger models reconverge faster in later training stages, while smaller models never actually reconverge. |
| Outcome: | The proposed model size and training checkpoints influence convergence of language models under different seeds. |
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| Challenge: | Existing methods to detect cross-linguistic associations are not effective, but their effects are minor. |
| Approach: | They propose a method to measure cross-linguistic associations by controlling for the influence of language family and geographic proximity within a large concept-aligned, cross-lingual lexicon. |
| Outcome: | The proposed method shows that it is small, but it is unsurprisingly small (less than 0.5% on average). |
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| Challenge: | Existing theories of communication cost are based on the length of an utterance, but they are not based upon the frequency of the utterant. |
| Approach: | They propose a method to minimize CCH's cost by comparing language lengths to surprisal's expectation and variance-to-mean ratios. |
| Outcome: | The proposed method does not minimize CCH’s cost, but rather a lower bound, which we term CCH-lower. |
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| Challenge: | Existing measures of linguistic complexity are relatively coarse-see, for example, Moran and Blasi (2014) and 2 below for reviews. |
| Approach: | They propose to measure bits per phoneme using the negative log-probability of a word in a language model and a collection of 1016 basic concept words across 106 languages. |
| Outcome: | The proposed measure allows a cross-linguistic comparison of phonotactic complexity across languages. |
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| Challenge: | lexical meanings are mapped to wordforms by usage pressures and constraints on sequences of symbols. |
| Approach: | They propose a coding-theoretic view of the lexicon and a novel generative statistical model to quantify its compressibility under various constraints. |
| Outcome: | The proposed model shows that (compositional) morphology and graphotactics can account for most of the complexity of natural codes—as measured by code length. |
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| Challenge: | Prior work has shown that the information carried by prosodic features is substantially redundant with that carried by the surrounding words. |
| Approach: | They examine the time scale of this relationship, studying how it varies with the length of past and future contexts. |
| Outcome: | The results show that prosody features show some redundancy with future words, but only with a short scale of 1-2 words, consistent with reports of incremental short-term planning in language production. |
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| Challenge: | a discrepancy in probabilistic language generators has puzzled the language generation community for years . |
| Approach: | They propose a method for local typical sampling to enforce a conditional entropy criterion for probabilistic models. |
| Outcome: | The proposed method can provide new insights into why high-probability texts can be dull or repetitive. |
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| Challenge: | The uniform information density hypothesis posits a preference among language users for utterances structured such that information is distributed uniformly across a signal. |
| Approach: | They propose to test the hypothesis by using reading time and acceptability data to examine the effect of surprisal on language comprehension and acceptabilities. |
| Outcome: | The proposed hypothesis makes predictions about language comprehension and linguistic acceptability . |
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| Challenge: | Language models estimate a probability distribution over strings in a natural language . many recent linguistic studies have been incorrectly computing word probabilities . |
| Approach: | They propose to use the correct method to compute word probabilities . they highlight issues when relying on models that use end-of-word tokenisers . |
| Outcome: | Empirically, correcting the widespread bug affects measured outcomes in sentences and lexical optimisation analyses. |
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| Challenge: | Text generation relies heavily on decoding algorithms that sample strings from a language model distribution. |
| Approach: | They propose to introduce globally-normalised versions of traditional decoding methods and propose an independent Metropolis-Hastings algorithm to approximate sampling from globally-averaged distributions without explicitly computing them. |
| Outcome: | The proposed method approximates the distributions without explicitly computing them. |
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| Challenge: | Neural networks are a pillar of modern NLP systems, but their inner workings are poorly understood. |
| Approach: | They propose a probe metric that reflects the trade-off between probe complexity and performance: the Pareto hypervolume. |
| Outcome: | The proposed probe metric conforms to accepted rankings among contextual representations, and is more complex than other probe tasks. |
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| Challenge: | We generalize the Bar-Hillel intersection construction so that the given WFSA may contain -arcs. |
| Approach: | They propose a construction that generalizes the Bar- Hillel in the case the desired automaton has -arcs and generalize the weighted extension so that the given WFSA may contain arcs. |
| Outcome: | The proposed construction can encode the structure of both the input automaton and grammar while retaining the asymptotic size of the original construction. |
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| Challenge: | A longstanding debate in semiotics centers on the relationship between linguistic signs and their corresponding semantics: is there an arbitrary relationship between word forms and their meaning, or does some systematic phenomenon pervade? |
| Approach: | They propose to quantify the systematicity of the sign using mutual information and recurrent neural networks to examine 106 languages. |
| Outcome: | The proposed model reduces entropy in a word form conditioned on its semantic representation and recovers English examples of systematic affixes. |
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| Challenge: | Existing studies evaluating generalisation performance on large language models focuses on a single out-of-distribution dataset . |
| Approach: | They examine whether OOD generalisation results generalise across multiple OOD testsets throughout a finetuning run and then evaluate the partial correlation of results . |
| Outcome: | The proposed model achieves high scores on multiple OOD testsets, regressing out in-domain performance. |
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| Challenge: | lexical studies of word processing and lexicon access provide evidence of preferred nature of word-initial versus word-final segments . conjecture that languages have evolved to provide more information earlier in words is based on existing methods . |
| Approach: | They propose to use a new method to assess the informativeness of word-initial versus word-final segments. |
| Outcome: | The proposed measures avoid the confounds found in existing methods. |
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| Challenge: | Existing methods for probing are limited and lack understanding of their limitations and weaknesses. |
| Approach: | They propose a strategy for input-level intervention on naturalistic sentences . they use morpho-syntactic features of a sentence to intervene on the rest of the sentence . |
| Outcome: | The proposed approach allows for input-level intervention on naturalistic sentences while keeping the rest of the sentence unchanged. |
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| Challenge: | a recent study has compared real and counterfactual word orders, but one functional pressure has been overlooked . a study of 10 typologically diverse languages shows that real word orders have greater uniformity than reverse word orders . |
| Approach: | They propose to test whether a pressure for UID may have influenced word order patterns cross-linguistically. |
| Outcome: | The proposed model shows that real orders have greater uniformity than reverse orders among SVO languages. |
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| Challenge: | Existing multilingual speech corpora have limited data in many languages . existing corpus is limited to a small number of languages with available data . |
| Approach: | They propose a large-scale phonetic typology corpus with phoneme-level labels and phoneme alignments in 690 readings spanning 635 languages. |
| Outcome: | The proposed corpus covers 635 languages and includes acoustic-phonetic measures of vowels and sibilants. |
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| Challenge: | lexical identity and prosody are well-studied parameters of linguistic variation, but they are difficult to predict in tonal languages. |
| Approach: | They propose to characterize the relationship between lexical identity and prosody using information theory to estimate mutual information between the text and pitch curves. |
| Outcome: | The proposed hypothesis supports perspectives that view linguistic typology as gradient, rather than categorical. |
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| Challenge: | Existing studies suggest partial redundancy between prosody and linguistic information. |
| Approach: | They use large language models to estimate how much information is redundant between prosody and the words themselves. |
| Outcome: | The proposed model can predict prosodic features across prosodic features, including intensity, duration, pauses, and pitch contours. |
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| Challenge: | phonological form and meaning of nouns can provide imperfect clues, but they can also be indicative of grammatical gender. |
| Approach: | They propose a method to measure how much information can be gleamed from knowing the form and/or meaning of nouns. |
| Outcome: | The proposed method provides additional quantitative support for a classic linguistic finding that form and meaning are relevant for the classification of nouns into declensions. |
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| Challenge: | Throughout human evolution, countless languages have evolved, each with unique features. |
| Approach: | They analysed a corpus of 600 languages to find strong evidence for a surprisal–duration trade-off between languages and languages. |
| Outcome: | The proposed model shows that phones are produced faster in languages where they are less surprising and vice versa. |
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| Challenge: | Tokenisation is the first step required to use a language model. |
| Approach: | They propose to find tokenisers which maximise the compression of a text by either finding a vocabulary directly or selecting a sequence of merge operations. |
| Outcome: | The proposed tokenisation methods are able to find tokenisers that maximise compression of a text. |
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| Challenge: | Prosody—the melody of speech—conveys critical information often not captured by the words or text of a message. |
| Approach: | They propose an information-theoretic approach to quantify how much is conveyed by prosody that is not recoverable from text alone. |
| Outcome: | The proposed framework can quantify how much is conveyed by prosody that is not recoverable from text alone and crucially, what prosody conveys. |
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| Challenge: | a recent paper suggests that probing should be seen as approximating a mutual information. |
| Approach: | They propose a Bayesian mutual information framework that probes probing representations from the perspective of Bayes' agents. |
| Outcome: | The proposed framework allows for more intuitive results in scenarios with finite data. |
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| Challenge: | Modern language models define probabilities over character-strings, but in practice, it does . Ideally, the choice of the tokeniser should not affect the probability assigned to the underlying character- string. |
| Approach: | They quantify a type of tokenisation bias by framing it as a causal effect and estimating it using the regression discontinuity design. |
| Outcome: | The proposed model can estimate tokenisation bias by comparing subwords around arbitrary cutoff points. |
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| Challenge: | Existing studies have shown that surprisal theory ignores the possibility of similarity between words and treats them as distinct entities. |
| Approach: | They propose a new measure of comprehension effort called information value that accounts for communicative equivalences between possible continuations. |
| Outcome: | The proposed measure of comprehension effort is based on the diversity index of the diversity of communicative units. |
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| Challenge: | Neural networks are the backbone of modern stateof-the-art natural language processing systems. |
| Approach: | They propose an information-theoretic operationalization of probing as estimating mutual information that contradicts received wisdom . they evaluate on a set of ten typologically diverse languages often underrepresented in NLP research—plus English—totalling eleven languages. |
| Outcome: | The proposed model outperforms existing models on ten typologically diverse languages and English on 11 languages. |
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| Challenge: | a recent study examined how much information a model's representations contain . a new approach to probing is to look exactly like the component . |
| Approach: | They propose a new probing principle that aims to estimate how much information a model could extract from its representations. |
| Outcome: | The proposed probes extract syntactic information from the representations of a neural network . the proposed probe is based on the architectural bottleneck principle . |
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| Challenge: | The Universal Morphology project provides broad-coverage instantiated morphological inflection tables for hundreds of diverse languages. |
| Approach: | They propose a language-independent feature schema for rich morphological annotation and a type-level resource of annotated data in diverse languages realizing that schema. |
| Outcome: | The proposed schema has added 66 new languages, including 24 endangered languages. |
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| Challenge: | Fig. 1 shows how left-corner transformations remove left recursion from context-free grammars . a common use case is to remove left-recursed grammars, which is necessary for top-down parsing . |
| Approach: | They generalize left-corner transformations to support semiring-weighted production rules . they also provide finer-grained control over which left corners may be moved . |
| Outcome: | The proposed transformation removes left recursion from context-free grammars . it also provides finer-grained control over which left corners may be moved . |
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| Challenge: | In common law, the outcome of a new case is determined mostly by precedent cases, rather than by existing statutes. |
| Approach: | They propose to model the argumentation of precedent cases and compare them to a case out-come classification task to determine how the precedent influences the outcome of a new case. |
| Outcome: | The proposed method compared arguments of two longstanding jurisprudential views on the European Court of Human Rights (ECtHR) and the precedent cases. |
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| Challenge: | a growing percentage of natural language processing tasks focus on the generation of text from probabilistic language models. |
| Approach: | They will provide a centralized discussion of critical considerations when choosing how to generate from a language model. |
| Outcome: | This tutorial will provide a centralized discussion of critical considerations when choosing how to generate from a language model. |
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| Challenge: | Recent theories of language optimality have tried to justify its prevalence, arguing that homophony enables the reuse of efficient wordforms and is thus beneficial for languages. |
| Approach: | They propose a new information-theoretic quantification of a language’s homophony: the sample Rényi entropy. |
| Outcome: | The proposed method is more nuanced than either Piantadosi et al.'s or Trott and Bergen's results. |
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| Challenge: | Recent studies show that in-context learning and few-shot fine-tuning can generalize well out-of-domain. |
| Approach: | They compare few-shot fine-tuning and in-context learning for task adaptation . they find that both approaches generalize similarly, but exhibit large variation . |
| Outcome: | The proposed methods outperform in-context learning and few-shot fine-tuning with OPT models of different sizes. |
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| Challenge: | a standard probabilistic model for language generation has likely not yet learnt many semantic or syntactic rules of natural language, making it difficult to estimate the probability distribution over next tokens. |
| Approach: | They propose to initialise bias terms in a model's final linear layer with the log-unigram distribution and use it to output the unigram frequency statistics as prior knowledge. |
| Outcome: | The proposed method improves learning efficiency and improves overall performance. |
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| Challenge: | Probing is a method of investigating the encoding of knowledge in contextual representations. |
| Approach: | They propose to kernelize a metric and develop a non-linear variant with an identical number of parameters by using a kernel-based probe. |
| Outcome: | The proposed probe learns only linear transformations and achieves statistically significant performance improvement over baseline in all languages. |
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| Challenge: | Using sampling adapters can improve the quality of the generated text. |
| Approach: | They propose a framework for understanding sampling adapters and propose 'sampling adapters' they argue that the shift enforced by them can be viewed as a trade-off between precision and recall . |
| Outcome: | The proposed framework can be used to improve the quality of language models by modifying their distributions to improve their precision and recall. |
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| Challenge: | Lexical ambiguity is widespread in language, allowing for the reuse of economical word forms and thus making language more efficient. |
| Approach: | They propose two ways to estimate lexical ambiguity as the entropy of meanings a word can take . they validate this hypothesis by using WordNet and BERT . |
| Outcome: | The proposed method shows that on six high-resource languages, there are significant correlations between the estimate and the number of synonyms a word has in WordNet. |
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| Challenge: | a lack of studies targeting naturalistic sentence-final reading behavior is likely to explain the lack of data on reading time (RT) data is omitted due to the confounding factors introduced by so-called "wrap-up effects" |
| Approach: | They propose to look for a link between “wrap-up effects” and information theoretic quantities such as word and context information content. |
| Outcome: | The proposed model omits data on words at the end of sentences or clauses to control for the confounding factors introduced by wrap-up effects. |