874 research outputs found
Self-Guided Contrastive Learning for BERT Sentence Representations
Although BERT and its variants have reshaped the NLP landscape, it still
remains unclear how best to derive sentence embeddings from such pre-trained
Transformers. In this work, we propose a contrastive learning method that
utilizes self-guidance for improving the quality of BERT sentence
representations. Our method fine-tunes BERT in a self-supervised fashion, does
not rely on data augmentation, and enables the usual [CLS] token embeddings to
function as sentence vectors. Moreover, we redesign the contrastive learning
objective (NT-Xent) and apply it to sentence representation learning. We
demonstrate with extensive experiments that our approach is more effective than
competitive baselines on diverse sentence-related tasks. We also show it is
efficient at inference and robust to domain shifts.Comment: ACL 202
The full repertoire of Drosophila gustatory receptors for detecting an aversive compound.
The ability to detect toxic compounds in foods is essential for animal survival. However, the minimal subunit composition of gustatory receptors required for sensing aversive chemicals in Drosophila is unknown. Here we report that three gustatory receptors, GR8a, GR66a and GR98b function together in the detection of L-canavanine, a plant-derived insecticide. Ectopic co-expression of Gr8a and Gr98b in Gr66a-expressing, bitter-sensing gustatory receptor neurons (GRNs) confers responsiveness to L-canavanine. Furthermore, misexpression of all three Grs enables salt- or sweet-sensing GRNs to respond to L-canavanine. Introduction of these Grs in sweet-sensing GRNs switches L-canavanine from an aversive to an attractive compound. Co-expression of GR8a, GR66a and GR98b in Drosophila S2 cells induces an L-canavanine-activated nonselective cation conductance. We conclude that three GRs collaborate to produce a functional L-canavanine receptor. Thus, our results clarify the full set of GRs underlying the detection of a toxic tastant that drives avoidance behaviour in an insect
Prompt-Augmented Linear Probing: Scaling Beyond The Limit of Few-shot In-Context Learners
Through in-context learning (ICL), large-scale language models are effective
few-shot learners without additional model fine-tuning. However, the ICL
performance does not scale well with the number of available training samples
as it is limited by the inherent input length constraint of the underlying
language model. Meanwhile, many studies have revealed that language models are
also powerful feature extractors, allowing them to be utilized in a black-box
manner and enabling the linear probing paradigm, where lightweight
discriminators are trained on top of the pre-extracted input representations.
This paper proposes prompt-augmented linear probing (PALP), a hybrid of linear
probing and ICL, which leverages the best of both worlds. PALP inherits the
scalability of linear probing and the capability of enforcing language models
to derive more meaningful representations via tailoring input into a more
conceivable form. Throughout in-depth investigations on various datasets, we
verified that PALP significantly enhances the input representations closing the
gap between ICL in the data-hungry scenario and fine-tuning in the
data-abundant scenario with little training overhead, potentially making PALP a
strong alternative in a black-box scenario.Comment: AAAI 202
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