Teemu Vahtola


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Toward the Modular Training of Controlled Paraphrase Adapters
Teemu Vahtola | Mathias Creutz
Proceedings of the 1st Workshop on Modular and Open Multilingual NLP (MOOMIN 2024)

Controlled paraphrase generation often focuses on a specific aspect of paraphrasing, for instance syntactically controlled paraphrase generation. However, these models face a limitation: they lack modularity. Consequently adapting them for another aspect, such as lexical variation, needs full retraining of the model each time. To enhance the flexibility in training controlled paraphrase models, our proposition involves incrementally training a modularized system for controlled paraphrase generation for English. We start by fine-tuning a pretrained language model to learn the broad task of paraphrase generation, generally emphasizing meaning preservation and surface form variation. Subsequently, we train a specialized sub-task adapter with limited sub-task specific training data. We can then leverage this adapter in guiding the paraphrase generation process toward a desired output aligning with the distinctive features within the sub-task training data. The preliminary results on comparing the fine-tuned and adapted model against various competing systems indicates that the most successful method for mastering both general paraphrasing skills and task-specific expertise follows a two-stage approach. This approach involves starting with the initial fine-tuning of a generic paraphrase model and subsequently tailoring it for the specific sub-task.


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Guiding Zero-Shot Paraphrase Generation with Fine-Grained Control Tokens
Teemu Vahtola | Mathias Creutz | Jrg Tiedemann
Proceedings of the 12th Joint Conference on Lexical and Computational Semantics (*SEM 2023)

Sequence-to-sequence paraphrase generation models often struggle with the generation of diverse paraphrases. This deficiency constrains the viability of leveraging paraphrase generation in different Natural Language Processing tasks. We propose a translation-based guided paraphrase generation model that learns useful features for promoting surface form variation in generated paraphrases from cross-lingual parallel data. Our proposed method leverages multilingual neural machine translation pretraining to learn zero-shot paraphrasing. Furthermore, we incorporate dedicated prefix tokens into the training of the machine translation models to promote variation. The prefix tokens are designed to affect various linguistic features related to surface form realizations, and can be applied during inference to guide the decoding process towards a desired solution. We assess the proposed guided model on paraphrase generation in three languages, English, Finnish, and Swedish, and provide analysis on the feasibility of the prefix tokens to guided paraphrasing. Our analysis suggests that the attributes represented by the prefix tokens are useful in promoting variation, by pushing the paraphrases generated by the guided model to diverge from the input sentence while preserving semantics conveyed by the sentence well.


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It Is Not Easy To Detect Paraphrases: Analysing Semantic Similarity With Antonyms and Negation Using the New SemAntoNeg Benchmark
Teemu Vahtola | Mathias Creutz | Jörg Tiedemann
Proceedings of the Fifth BlackboxNLP Workshop on Analyzing and Interpreting Neural Networks for NLP

We investigate to what extent a hundred publicly available, popular neural language models capture meaning systematically. Sentence embeddings obtained from pretrained or fine-tuned language models can be used to perform particular tasks, such as paraphrase detection, semantic textual similarity assessment or natural language inference. Common to all of these tasks is that paraphrastic sentences, that is, sentences that carry (nearly) the same meaning, should have (nearly) the same embeddings regardless of surface form. We demonstrate that performance varies greatly across different language models when a specific type of meaning-preserving transformation is applied: two sentences should be identified as paraphrastic if one of them contains a negated antonym in relation to the other one, such as “I am not guilty” versus “I am innocent”.We introduce and release SemAntoNeg, a new test suite containing 3152 entries for probing paraphrasticity in sentences incorporating negation and antonyms. Among other things, we show that language models fine-tuned for natural language inference outperform other types of models, especially the ones fine-tuned to produce general-purpose sentence embeddings, on the test suite. Furthermore, we show that most models designed explicitly for paraphrasing are rather mediocre in our task.

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Modeling Noise in Paraphrase Detection
Teemu Vahtola | Eetu Sjöblom | Jörg Tiedemann | Mathias Creutz
Proceedings of the Thirteenth Language Resources and Evaluation Conference

Noisy labels in training data present a challenging issue in classification tasks, misleading a model towards incorrect decisions during training. In this paper, we propose the use of a linear noise model to augment pre-trained language models to account for label noise in fine-tuning. We test our approach in a paraphrase detection task with various levels of noise and five different languages. Our experiments demonstrate the effectiveness of the additional noise model in making the training procedures more robust and stable. Furthermore, we show that this model can be applied without further knowledge about annotation confidence and reliability of individual training examples and we analyse our results in light of data selection and sampling strategies.


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Grammatical Error Generation Based on Translated Fragments
Eetu Sjöblom | Mathias Creutz | Teemu Vahtola
Proceedings of the 23rd Nordic Conference on Computational Linguistics (NoDaLiDa)

We perform neural machine translation of sentence fragments in order to create large amounts of training data for English grammatical error correction. Our method aims at simulating mistakes made by second language learners, and produces a wider range of non-native style language in comparison to a state-of-the-art baseline model. We carry out quantitative and qualitative evaluation. Our method is shown to outperform the baseline on data with a high proportion of errors.

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Coping with Noisy Training Data Labels in Paraphrase Detection
Teemu Vahtola | Mathias Creutz | Eetu Sjöblom | Sami Itkonen
Proceedings of the Seventh Workshop on Noisy User-generated Text (W-NUT 2021)

We present new state-of-the-art benchmarks for paraphrase detection on all six languages in the Opusparcus sentential paraphrase corpus: English, Finnish, French, German, Russian, and Swedish. We reach these baselines by fine-tuning BERT. The best results are achieved on smaller and cleaner subsets of the training sets than was observed in previous research. Additionally, we study a translation-based approach that is competitive for the languages with more limited and noisier training data.