Lachlan O’Neill


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Models Teaching Models: Improving Model Accuracy with Slingshot Learning
Lachlan O’Neill | Nandini Anantharama | Satya Borgohain | Simon D. Angus
Proceedings of the 17th Conference of the European Chapter of the Association for Computational Linguistics

One significant obstacle to the successful application of machine learning to real-world data is that of labeling: it is often prohibitively expensive to pay an ethical amount for the human labor required to label a dataset successfully. Human-in-the-loop techniques such as active learning can reduce the cost, but the required human time is still significant and many fixed costs remain. Another option is to employ pre-trained transformer models as labelers at scale, which can yield reasonable accuracy and significant cost savings. However, such models can still be expensive to use due to their high computational requirements, and the opaque nature of these models is not always suitable in applied social science and public use contexts. We propose a novel semi-supervised method, named Slingshot Learning, in which we iteratively and selectively augment a small human-labeled dataset with labels from a high-quality “teacher” model to slingshot the performance of a “student” model in a cost-efficient manner. This reduces the accuracy trade-off required to use these simpler algorithms without disrupting their benefits, such as lower compute requirements, better interpretability, and faster inference. We define and discuss the slingshot learning algorithm and demonstrate its effectiveness on several benchmark tasks, using ALBERT to teach a simple Naive Bayes binary classifier. We experimentally demonstrate that Slingshot learning effectively decreases the performance gap between the teacher and student models. We also analyze its performance in several scenarios and compare different variants of the algorithm.


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CANarEx: Contextually Aware Narrative Extraction for Semantically Rich Text-as-data Applications
Nandini Anantharama | Simon Angus | Lachlan O’Neill
Findings of the Association for Computational Linguistics: EMNLP 2022

Narrative modelling is an area of active research, motivated by the acknowledgement of narratives as drivers of societal decision making. These research efforts conceptualize narratives as connected entity chains, and modeling typically focuses on the identification of entities and their connections within a text. An emerging approach to narrative modelling is the use of semantic role labeling (SRL) to extract Entity-Verb-Entity (E-V-Es) tuples from a text, followed by dimensionality reduction to reduce the space of entities and connections separately. This process penalises the semantic richness of narratives and discards much contextual information along the way. Here, we propose an alternate narrative extraction approach - CANarEx, incorporating a pipeline of common contextual constructs through co-reference resolution, micro-narrative generation and clustering of these narratives through sentence embeddings. We evaluate our approach through testing the recovery of “narrative time-series clusters”, mimicking a desirable text-as-data task. The evaluation framework leverages synthetic data generated using a GPT-3 model. The GPT-3 model is trained to generate similar sentences using a large dataset of news articles. The synthetic data maps to three topics in the news dataset. We then generate narrative time-series document cluster representations by mapping the synthetic data to three distinct signals synthetically injected into the testing corpus. Evaluation results demonstrate the superior ability of CANarEx to recover narrative time-series through reduced MSE and improved precision/recall relative to existing methods. The validity is further reinforced through ablation studies and qualitative analysis.