2,546 research outputs found
Second-Order NLP Adversarial Examples
Adversarial example generation methods in NLP rely on models like language
models or sentence encoders to determine if potential adversarial examples are
valid. In these methods, a valid adversarial example fools the model being
attacked, and is determined to be semantically or syntactically valid by a
second model. Research to date has counted all such examples as errors by the
attacked model. We contend that these adversarial examples may not be flaws in
the attacked model, but flaws in the model that determines validity. We term
such invalid inputs second-order adversarial examples. We propose the
constraint robustness curve and associated metric ACCS as tools for evaluating
the robustness of a constraint to second-order adversarial examples. To
generate this curve, we design an adversarial attack to run directly on the
semantic similarity models. We test on two constraints, the Universal Sentence
Encoder (USE) and BERTScore. Our findings indicate that such second-order
examples exist, but are typically less common than first-order adversarial
examples in state-of-the-art models. They also indicate that USE is effective
as constraint on NLP adversarial examples, while BERTScore is nearly
ineffectual. Code for running the experiments in this paper is available at
https://github.com/jxmorris12/second-order-adversarial-examples.Comment: 8 page
Reevaluating Adversarial Examples in Natural Language
State-of-the-art attacks on NLP models lack a shared definition of a what
constitutes a successful attack. We distill ideas from past work into a unified
framework: a successful natural language adversarial example is a perturbation
that fools the model and follows some linguistic constraints. We then analyze
the outputs of two state-of-the-art synonym substitution attacks. We find that
their perturbations often do not preserve semantics, and 38% introduce
grammatical errors. Human surveys reveal that to successfully preserve
semantics, we need to significantly increase the minimum cosine similarities
between the embeddings of swapped words and between the sentence encodings of
original and perturbed sentences.With constraints adjusted to better preserve
semantics and grammaticality, the attack success rate drops by over 70
percentage points.Comment: 15 pages; 9 Tables; 5 Figure
Text Embeddings Reveal (Almost) As Much As Text
How much private information do text embeddings reveal about the original
text? We investigate the problem of embedding \textit{inversion},
reconstructing the full text represented in dense text embeddings. We frame the
problem as controlled generation: generating text that, when reembedded, is
close to a fixed point in latent space. We find that although a na\"ive model
conditioned on the embedding performs poorly, a multi-step method that
iteratively corrects and re-embeds text is able to recover of
text inputs exactly. We train our model to decode text
embeddings from two state-of-the-art embedding models, and also show that our
model can recover important personal information (full names) from a dataset of
clinical notes. Our code is available on Github:
\href{https://github.com/jxmorris12/vec2text}{github.com/jxmorris12/vec2text}.Comment: Accepted at EMNLP 202
Tree Prompting: Efficient Task Adaptation without Fine-Tuning
Prompting language models (LMs) is the main interface for applying them to
new tasks. However, for smaller LMs, prompting provides low accuracy compared
to gradient-based finetuning. Tree Prompting is an approach to prompting which
builds a decision tree of prompts, linking multiple LM calls together to solve
a task. At inference time, each call to the LM is determined by efficiently
routing the outcome of the previous call using the tree. Experiments on
classification datasets show that Tree Prompting improves accuracy over
competing methods and is competitive with fine-tuning. We also show that
variants of Tree Prompting allow inspection of a model's decision-making
process.Comment: Both first authors contributed equally; accepted to EMNLP 202
Annular electroconvection with shear
We report experiments on convection driven by a radial electrical force in
suspended annular smectic A liquid crystal films. In the absence of an
externally imposed azimuthal shear, a stationary one-dimensional (1D) pattern
consisting of symmetric vortex pairs is formed via a supercritical transition
at the onset of convection. Shearing reduces the symmetries of the base state
and produces a traveling 1D pattern whose basic periodic unit is a pair of
asymmetric vortices. For a sufficiently large shear, the primary bifurcation
changes from supercritical to subcritical. We describe measurements of the
resulting hysteresis as a function of the shear at radius ratio . This simple pattern forming system has an unusual combination of
symmetries and control parameters and should be amenable to quantitative
theoretical analysis.Comment: 12 preprint pages, 3 figures in 2 parts each. For more info, see
http://mobydick.physics.utoronto.c
Adoption of Participatory Rural Appraisal: A Case Study from China
There are many models of technology transfer. They vary from the linear scientist-extension worker-farmers model to the integrative natural resource management model (Jiggins, 1993). International experience has shown that for small holding farmers in developing countries a farmer driven model based on participatory approaches (the Participatory Rural Appraisal (PRA) Model) is more effective and efficient
GRB Polarimetry with POET
POET (Polarimeters for Energetic Transients) represents a concept for a Small Explorer (SMEX) satellite mission, whose principal scientific goal is to understand the structure of GRB sources through sensitive Xâray and Îłâray polarization measurements. The payload consists of two wide fieldâofâview (FoV) instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2â15 keV and a high energy polarimeter (GammaâRay Polarimeter Experiment or GRAPE) that would measure polarization in the 60â500 keV energy range. The POET spacecraft provides a zenithâpointed platform for maximizing the exposure to deep space. Spacecraft rotation provides a means of effectively dealing with any residual systematic effects in the polarization response. POET provides sufficient sensitivity and sky coverage to measure statistically significant polarization (for polarization levels in excess of 20%) for âŒ80 GRBs in a twoâyear mission. High energy polarization data would also be obtained for SGRs, solar flares, pulsars and other sources of astronomical interest
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