A Closer Look At Feature Space Data Augmentation For Few-Shot Intent Classification

10/09/2019 ∙ by Varun Kumar, et al. ∙ Amazon 0

New conversation topics and functionalities are constantly being added to conversational AI agents like Amazon Alexa and Apple Siri. As data collection and annotation is not scalable and is often costly, only a handful of examples for the new functionalities are available, which results in poor generalization performance. We formulate it as a Few-Shot Integration (FSI) problem where a few examples are used to introduce a new intent. In this paper, we study six feature space data augmentation methods to improve classification performance in FSI setting in combination with both supervised and unsupervised representation learning methods such as BERT. Through realistic experiments on two public conversational datasets, SNIPS, and the Facebook Dialog corpus, we show that data augmentation in feature space provides an effective way to improve intent classification performance in few-shot setting beyond traditional transfer learning approaches. In particular, we show that (a) upsampling in latent space is a competitive baseline for feature space augmentation (b) adding the difference between two examples to a new example is a simple yet effective data augmentation method.



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1 Introduction

Virtual artificial assistants with natural language understanding (NLU) support a variety of functionalities. Throughout the lifespan of the deployed NLU systems, new functionalities with new categories, are regularly introduced. While techniques such as active learning 

Peshterliev et al. (2018)

, semi-supervised learning 

Cho et al. (2019b) are used to improve the performance of existing functionalities, performance for new functionalities suffers from the data scarcity problem.

Recently, Few-Shot Learning has been explored to address the problem of generalizing from a few examples per category. While it has been extensively studied Koch et al. (2015); Snell et al. (2017); Vinyals et al. (2016)

for image recognition, a little attention has been paid to improve NLU performance in the low-data regime. Moreover, researchers have been mostly working on the unrealistic setting that considers tasks with few categories unseen during (pre)training, each with only a few examples, and introduces new categories during test time. We argue that a more realistic setting is Few-Shot Integration (FSI) where new categories with limited training data are introduced into an existing system with mature categories. FSI is well aligned with the goal of lifelong learning of conversational agents and measures the performance in a real-life system setting when only a few examples of a new class are added to the existing data from the old classes. To address the poor generalization in data scare scenarios, several pre-training methods such as ELMo 

Peters et al. (2018), Generative pre-trained Transformer Radford et al. (2018), BERT  Devlin et al. (2018), have been proposed which are trained on a large amount of unannotated text data. Such pre-trained models can be fine-tuned on a particular NLP task and have shown to greatly improve generalization. However, in FSI setting where only a handful of examples are provided, building accurate NLU model is still a challenging task.

In this paper, we focus on Feature space Data Augmentation (FDA) methods to improve the classification performance of the categories with limited data. We study six widely different feature space data augmentation methods: 1) upsampling in the feature space Upsample, 2) random perturbation Perturb, 3) extrapolation Devries and Taylor (2017) Extra, 4) conditional variational auto-encoder (CVAE) Kingma and Welling (2013) CVAE, 5) delta encoder that have been especially designed to work in the few-shot learning setting Schwartz et al. (2018) Delta, 6) linear delta which is a linear version of the delta encoder Linear. While Upsample, Perturb, Extra and Linear doesn’t require any training beyond hyper-parameter optimization, Delta and CVAE

are trained deep neural network generators.

We compare these six FDA techniques on two open datasets for Intent Classification (IC) : SNIPS Coucke et al. (2018) and Facebook Dialog corpus Gupta et al. (2018). We show that BERT combined with Linear

data augmentation provides an effective method to bootstrap accurate intent classifiers with limited training data. We make the following contributions:

  1. We propose the FSI evaluation, a relaxation of the few-shot learning setting that aims to better model the requirement of modern NLU systems. We provide a comprehensive evaluation of FSI for text classification and show that Upsample and Perturb are simple yet efficient baselines that are often neglected in few-shot learning evaluations.

  2. We provide an in-depth analysis of various FDA methods. We show that complex methods such as Delta and CVAE do not always improve over simple methods like Linear, and the performance heavily depends on the feature extractor.

  3. Finally, we provide guidance on when and how to apply FDA for FSI. We show that FDA consistently provides gains on top of the unsupervised pre-training methods such as BERT in FSI setting.

2 Related work

Few-shot learning

has been studied extensively in the computer vision domain. In particular, several metric learning based methods

Koch et al. (2015); Vinyals et al. (2016); Snell et al. (2017); Rippel et al. (2015) has been proposed for few-shot classification where a model first learns an embedding space and then a simple metric is used to classify instances of new categories via proximity to the few labeled training examples embedded in the same space. In addition to metric-learning, several meta-learning based approaches  Ravi and Larochelle (2016); Li et al. (2017); Finn et al. (2017) have been proposed for few-shot classification on unseen classes.

Recently, Few-Shot Learning on text data has been explored using metric learning Yu et al. (2018); Jiang et al. (2018). In Yu et al. (2018), authors propose to learn a weighted combination of metrics obtained from meta-training tasks for a newly seen few-shot task. Similarly, in Cheng et al. (2019), authors propose to use meta-metric-learning to learn task-specific metric that can handle imbalanced datasets.

Generative models are also widely used to improve classification performance by data augmentation. For example, generative models are used for data augmentation in image classification  Mehrotra and Dukkipati (2017); Antoniou et al. (2018); Zhang et al. (2018), text classification Gupta (2019)

, anomaly detection

Lim et al. (2018). Data augmentation through deformation of an image has been known to be very effective for image recognition. More advanced approaches rely on Auto-Encoders (AEs) or Generative Adversarial Networks (GANs). For example, in Mehrotra and Dukkipati (2017) the authors combine metric-learning with data augmentation using GANs for few-shot learning. However, classical generative approaches require a significant amount of training data to be able to generate good enough examples that will improve classification accuracy. To overcome this challenge, (Hariharan and Girshick, 2017) proposed to augment the training data in the feature space. This both eases the generation problem and enforces generation of discriminative examples. In addition, the authors propose to transfer deformations from base classes to new classes, which allows circumventing the data scarcity problem for new classes. Finally, in  Schwartz et al. (2018)

, authors used an Autoencoder to encode transformations between pairs of examples of the same class and apply them to an example of the new class.

Generative models are a good candidate for FSI tasks, as one can just combine the generated data for new classes with the old classes training data  Hariharan and Girshick (2017); Wang et al. (2018)

. For text classification, several text generation based data augmentation techniques have also been explored  

Hou et al. (2018); Zhao et al. (2019); Guu et al. (2018); Yoo et al. (2018); Cho et al. (2019a). However, generating discrete sequences, e.g. text, is known to be quite difficult and requires lots of training data. That is why, in this paper, we focus on generative models, which augment data in latent(feature) space to solve a few-shot integration problem for text classification.

3 Data Augmentation in Feature Space

(a) Learning the feature space
(b) Learning with augmented data
Figure 1: Data augmentation in the feature space

Feature space data Augmentation (FDA) is an effective method to improve classification performance on different ML tasks Chawla et al. (2002); Hariharan and Girshick (2017); Devries and Taylor (2017); Guo et al. (2019). As shown on Figure 1, FDA techniques usually work by first learning a data representation or feature extractor, and then generating new data for the low resource class in the feature space. After generating data, a classifier is trained with real and augmented data.

For IC, we finetune a pre-trained English BERT-Base uncased model 111https://github.com/huggingface/pytorch-transformers to build our feature extractor. The BERT model has layers, hidden states, and

heads. We use the pooled representation of the hidden state of the first special token ([CLS]) as the sentence representation. A dropout probability of

is applied to the sentence representation before passing it to the 1-layer Softmax classifier. BERT Encoder and MLP classifier are fine-tuned using cross-entropy loss for IC task. Adam Kingma and Ba (2014) is used for optimization with an initial learning rate of .

For data augmentation, we apply six different FDA methods, described below, to generate new examples in the feature space. Finally, we train a 1- layer Softmax classifier as in the feature learning phase.

3.1 Upsampling

The simplest method to augment training data for underrepresented categories is to duplicate the existing training data. Upsampling is a well studied technique to handle the class imbalance problem Estabrooks et al. (2004). We show that for intents with limited labeled data, upsampling the existing data in latent space consistently improves model performance, and thus is a good baseline method for FDA techniques. We call this method Upsample.

3.2 Random Perturbation

Adding random noise to the existing training data is another simple yet effective data augmentation technique. Random perturbation data augmentation has been previously used to improve the performance of classification models as well as for sequence generation models. For example, Kurata et al. (2016)

applied additive and multiplicative perturbation to improve the text generation for data augmentation. In our experiments, we apply both additive and multiplicative perturbation to the existing training data. We sample noise from a uniform distribution [-1.0, 1.0]. We use

Perturb to refer to this method.

3.3 Conditional VAE

Conditional Variational Autoencoder (CVAE) is an extension of Variational Autoencoder (VAE) Kingma and Welling (2013)

which can be used to generate examples for a given category. All components of the model are conditioned on the category. First, we train CVAE on the sentence representations and then generate new examples by sampling from the latent distribution. The encoder and decoder sub-networks are implemented as multi-layer perceptrons with a single hidden layer of

units, where each layer is followed by a hyperbolic tangent activation. The encoder output is

-dimensional. Mean Square Error (MSE) loss function is used for reconstruction. All models are trained with Adam optimizer with the learning rate set to


3.4 Linear Delta

A simple method to generate new examples is to first learn the difference between a pair of examples, and then add this difference to another example. In this case, we first compute the difference between two examples from the same class and then add it to a third example also from the same class as shown in (1). We use Linear to refer to this method.


3.5 Extrapolation

In Devries and Taylor (2017), authors proposed to use extrapolation to synthesize new examples for a given class. They demonstrated that extrapolating between samples in feature space can be used to augment datasets. In extrapolation, a new example, is generated according to (2). In our experiments, we use . We call this method Extra.


3.6 Delta-Encoder

Delta-Encoder Schwartz et al. (2018) extends the idea of learning differences between two examples using an autoencoder-based model. It first extracts transferable intra-class deformations (deltas) between same-class pairs of training examples, then applies them to a few examples of a new class to synthesize samples from that class. Authors show that Delta-Encoder can learn transferable deformations from different source classes which can be used to generate examples for unseen classes. While the authors used Delta-Encoder to generate examples for unseen classes, in our experiments, for FSI, we also use the examples from the target class to the train both the feature extractor and the Delta-Encoder along with all other examples. Then we generate new examples for the target category using trained delta encoder. For data generation, we try two different approaches to select a source sentence pair.

  1. DeltaR: Sample a pair of sentences (, ) from a randomly selected class. DeltaR applies deltas from multiple source categories to synthesize new examples.

  2. DeltaS: Sample a pair of sentences (, ) from the target category. DeltaS applies deltas from the same target category.

The encoder and decoder sub-networks are implemented as multi-layer perceptrons with a single hidden layer of

units, where each layer is followed by a leaky ReLU activation (

). The encoder output is -dimensional. L1 loss is used as reconstruction loss. Adam optimizer is used with a learning rate of . A high dropout with a % rate is applied to all layers, to avoid the model memorizing examples.

4 Experiment

4.1 Datasets

We evaluate different FDA techniques on two public benchmark datasets, SNIPS Coucke et al. (2018), and Facebook Dialog corpus (FBDialog) Gupta et al. (2018). For SNIPS dataset, we use train, dev and test split provided by Goo et al. (2018) 222https://github.com/MiuLab/SlotGated-SLU.

SNIPS dataset contains intents which are collected from the Snips personal voice assistant. The training, development and test sets contain , and utterances, respectively. FBDialog has utterances that are focused on navigation, events, and navigation to events. FBDialog dataset also contains utterances with multiple intents as the root node. For our experiment, we exclude such utterances by removing utterances with COMBINED intent root node. This leads to training, development and testset utterances. Note that while SNIPS is a balanced dataset, FBDialog dataset is highly imbalanced with a maximum and a minimum of training examples per intent.

4.2 Simulating Few-Shot Integration

In virtual assistants, often a new intent development starts with very limited training data. To simulate the integration of a new intent, we randomly sample seed training examples from the new intent, referred to as target intent, and keep all the data from other intents. We also remove the target intent data from the development set. We train the feature extractor on the resulting training data, and then generate , examples using different augmentation methods for the target intent. To account for random fluctuations in the results, we repeat this process

times for a given target intent and report the average accuracy with the standard deviation. In all experiments, models are evaluated on the full test set.

Size Method SNIPS FBDialog
No Augmentation 98.14 (0.42) 94.99 (0.18)
5% Upsample 98.14 (0.47) 95.01 (0.16)
Perturb 98.26 (0.40) 94.98 (0.19)
Linear 98.14 (0.45) 95.02 (0.21)
Extra 98.14 (0.45) 95.02 (0.20)
CVAE 98.14 (0.45) 94.98 (0.24)
DeltaR 98.23 (0.46) 95.00 (0.22)
DeltaS 98.26 (0.42) 95.00 (0.20)
10% Upsample 98.14 (0.47) 94.94 (0.18)
Perturb 98.23 (0.41) 94.98 (0.24)
Linear 98.09 (0.50) 95.02 (0.18)
Extra 98.11 (0.49) 95.01 (0.19)
CVAE 98.20 (0.42) 94.99 (0.26)
DeltaR 98.26 (0.42) 94.99 (0.21)
DeltaS 98.23 (0.42) 94.97 (0.22)
20% Upsample 98.14 (0.45) 95.02 (0.12)
Perturb 98.14 (0.44) 94.99 (0.20)
Linear 98.17 (0.43) 95.05 (0.23)
Extra 98.14 (0.45) 95.07 (0.11)
CVAE 98.11 (0.44) 94.98 (0.23)
DeltaR 98.26 (0.40) 95.08 (0.19)
DeltaS 98.20 (0.46) 95.04 (0.22)
Table 1: IC accuracy on SNIPS and Facebook dataset with all training data, reported as mean (SD).

5 Results and Discussion

5.1 FDA For Data-Rich Classification

For both datasets, we generate , , and examples using different FDA methods. Then, we train a classifier using both generated as well as real data. Table 1 shows that augmenting data in feature space provides only minor improvements in classification accuracy. In particular, on SNIPS dataset, Pertub and DeltaR improve accuracy from to . On FBDialog dataset, DeltaR provides a minor gain, to over upsample baseline.

5.2 Impact Of The Number Of Seed Examples

To understand the impact of the number of seed examples, we vary it to , , , , , and for SNIPS’s AddToPlaylist. For each experiment, we generate examples using different FDA methods. Figure 2 shows that as the number of seed examples increases, the accuracy of the model goes up. We also observe that for a few seed examples - , Linear outperforms other FSA methods. Finally, gains are less significant after seed examples.

Figure 2: IC accuracy on SNIPS’s AddToPlaylist intent with varying number of seed examples. examples are generated using different FDA techniques. As indicated by the accuracy trend, increasing the seed examples leads to better performance.

5.3 Few-Shot Integration

We simulate FSI IC for all intents of SNIPS dataset. For FBDialog dataset, we run simulations on the six largest intents, viz. GetDirections, GetDistance, GetEstimatedArrival, GetEstimatedDuration, GetInfoTraffic, and GetEvent. Since, BERT generalizes well with just examples, to compare the effectiveness of different FDA methods, we use seed examples in FSI simulations. For each intent, we select seed training examples and use all training data for other intents.

Table 2 shows average accuracy for all intents’ FSI simulations. Results on individual intent’s FSI simulations can be found in Appendix’s Table 5 and Table 6. On both datasets, all FDA methods improve classification accuracy over no augmentation baseline. Also, Upsample provides huge gains over no augmentation baseline. Additionally, on both datasets, with augmented examples, Linear and DeltaS works better than Perturb and Upsample.

# Method SNIPS FBDialog
No Augmentation 87.46(2.87) 81.29(0.11)
100 Upsample 94.26(1.66) 84.34(1.84)
Perturb 94.18(1.74) 84.04(1.95)
CVAE 94.10(1.83) 84.10(1.94)
Linear 94.36(1.69) 84.31(1.9)
Extra 94.30(1.68) 84.13(1.83)
DeltaR 91.32(3.12) 81.97(0.76)
DeltaS 94.28(1.92) 83.50(1.92)
512 Upsample 95.68(0.86) 89.03(0.99)
Perturb 95.65(0.92) 89.02(0.99)
CVAE 95.46(1.03) 88.71(1.09)
Linear 95.87(0.87) 89.30(1.03)
Extra 95.82(0.89) 89.21(0.99)
DeltaR 95.33(1.56) 87.28(1.46)
DeltaS 95.88(1.04) 89.15(1.12)
Table 2: Average IC accuracy for all intents’ FSI simulations on SNIPS and FBDialog dataset. For each simulation, seed examples are used for target intent. Scores are reported as mean (SD). Refer to Appendix’s Table 5 and Table 6 for individual intents’ results.

5.4 Upsampling: Text Space vs Latent Space

# Method Overall Mean
No Augmentation 94.38(1.23)
100 Upsample 94.53(1.12)
Perturb 94.52(1.18)
CVAE 94.53(1.18)
Linear 94.53(1.12)
Extra 94.53(1.13)
DeltaR 94.62(1.16)
DeltaS 94.57(1.14)
512 Upsample 94.67(1.11)
Perturb 94.68(1.14)
CVAE 94.73(1.11)
Linear 94.67(1.11)
Extra 94.67(1.11)
DeltaR 94.88(1.12)
DeltaS 94.74(1.12)
Table 3: IC accuracy on SNIPS dataset in the FSI setting, reported as mean (SD). The seed examples are upsampled to to train the feature extractor. Refer to Appendix’s Table 7 for individual intents’ results.

In this section, we explore how upsampling in text space impacts performances as it is supposed to both improve the feature extractor and the linear classifier, compared to Upsample. To investigate whether upsampling in text space helps FDA, we upsampled the seed examples to and repeat the FSI experiments on all intents of the SNIPS dataset. Table 3 shows the mean accuracy of all intents FSI simulations results for different FDA techniques. FSI simulations scores for individual intents can be found in Appendix’s Table 7. We observe that upsampling in text space improves the no augmentation baseline for all intents. The mean accuracy score improves from to . We also observe that different FDA techniques further improve model accuracy. Interestingly, upsampling in text space helps DeltaR the most. Surprisingly, upsampling in latent space provides better performance than upsampling in the text space. In particular, without upsampling the seed examples to learn the feature extractor, the best score is for DeltaS, whereas with text space upsampling the best score decreases to . This decrease in performance is only seen with BERT and not with the Bi-LSTM feature extractor (see Table 4). We hypothesize that upsampling text data leads to BERT overfitting the target category which results in less generalized sentence representations. Overall, we found that augmentation in the latent space seems to work better with BERT, and is more effective than text space upsampling.

5.5 Effect Of The Pre-trained BERT Encoder

In FSI setting, Fine-Tuned BERT model provides very good generalization performance. For example, for SNIPS’s RateBookIntent (column Book in Table 5), it yields accuracy. Overall for BERT representations, Linear and DeltaS augmentation methods provide the best accuracy.

To investigate whether these augmentation improvements can be generalized to other sentence encoders, we experiment with a Bi-LSTM sentence encoder. For feature learning, we use a 1-layer Bi-LSTM encoder followed by a single layer softmax classifier. In our experiments, we use as hidden units and dimension Glove embeddings. For SNIPS dataset, we use examples of AddToPlaylist intent and for FB Dialog dataset, we use examples of GetDirections intent.

Table 4 shows intent accuracy for SNIPS and Facebook datasets. We find that, unlike BERT, in the FSI setting, the Bi-LSTM encoder provides a lower accuracy. In contrast to BERT FSI experiments, DeltaS performs worse than the Upsample and Perturb baselines. The main reason is that Delta-Encoder’s performance relies on a good feature extractor and with seed examples, the Bi-LSTM encoder fails to learn good sentence representations. To improve representation learning, we upsample utterances to and then train the feature extractor. Upsampling in text space improves the performance of both delta encoder methods, DeltaS, and DeltaR. Moreover, for both SNIPS’s AddToPlayList and FBDialog’s GetDirections intent, DeltaR outperforms all other FDA methods.

Size Method SNIPS’s AddToPlaylist FBDialog’s GetDirections
seed examples () 10 10
No Augmentation 80.07 (2.08) 90.17 (1.39) 87.44 (0.12) 87.94 (0.32)
100 Upsample 88.27 (1.74) 90.61 (1.52) 88.01 (0.26) 88.17 (0.32)
Perturb 88.03 (1.52) 90.86 (1.39) 88.01 (0.32) 88.25 (0.31)
Linear 88.14 (1.62) 91.06 (1.58) 88.05 (0.25) 88.26 (0.32)
Extra 88.09 (1.57) 90.74 (1.57) 88.10 (0.29) 88.20 (0.3)
CVAE 88.27 (2.08) 90.90 (1.69) 88.04 (0.24) 88.17 (0.32)
DeltaR 82.23 (2.21) 91.46 (1.19) 87.60 (0.23) 88.75 (0.43)
DeltaS 84.4 (2.74) 91.07 (1.44) 88.02 (0.22) 88.57 (0.36)
512 Upsample 91.41 (1.03) 91.61 (1.4) 88.68 (0.49) 88.40 (0.35)
Perturb 91.46 (0.99) 91.73 (1.32) 88.89 (0.57) 88.56 (0.39)
Linear 91.20 (1.28) 91.41 (1.52) 88.97 (0.65) 88.47 (0.33)
Extra 91.26 (1.22) 91.57 (1.55) 88.85 (0.61) 88.48 (0.37)
CVAE 91.39 (0.94) 91.44 (1.2) 89.02 (0.52) 88.48 (0.4)
DeltaR 87.09 (2.75) 92.97 (1.2)) 88.61 (0.35) 89.70 (0.53)
DeltaS 89.34 (1.48) 92.00 (1.25) 89.34 (0.4) 89.09 (0.51)
Table 4: IC accuracy on SNIPS’s AddToPlaylist and FBDialog’s GetDirections in the FSI setting, reported as mean (SD). A -layer Bi-LSTM model is used as a feature extractor. represents seed examples are upsampled to to train the feature extractor.

5.6 Is Delta-Encoder Effective On Text?

While on few-shot image classification, Delta-Encoder provides excellent generalization performance Schwartz et al. (2018) on unseen classes, on text classification, its performance is heavily dependent on the feature extractor. We observe that in most cases, DeltaR performs worse than DeltaS which suggests that unlike for few-shot image classification, Delta-Encoder fails to learn variations which can be applied to a different category. In addition, in FSI with BERT encoder, DeltaS performance is close to Linear. This indicates that in the low-data regime, simple subtraction between BERT sentence representations is a good proxy to learn intra-class variations. Upsampling data in text space improves Delta-Encoder performance for both BERT and Bi-LSTM encoders. As shown in Table 3, with upsampling in text space, DeltaR performs better than any other FDA method.

5.7 Qualitative Evaluation

Figure 3: seed examples
Figure 4: seed examples are upsampled to
Figure 5: t-SNE visualization of different data augmentation methods for AddToPlaylist intent. BERT encoder is used to learn sentence representations.

We observe significant accuracy improvements in all FSI experiments for all FDA methods. Since Upsample and Perturb also provide significant gains, it seems that most of the gains come from the fact that we are adding more data. However, in the FSI setting, Linear and DeltaS method consistently perform better than both Upsample and Perturb, which indicates that these methods generate more relevant data than just noise, and redundancy. Here, we focus on visualizing generated examples from Linear, DeltaS and DeltaR methods using t-SNE.

Figure 5 shows visualizations for SNIPS’s AddToPlaylist generated sentence representations using different FDA methods. We use seed examples of AddToPlaylist and use BERT as sentence encoder. While data generated by Linear and Extra are close to the real examples, DeltaS and DeltaR generated examples form two different clusters. Since, Delta-Encoder performance improves when seed examples are upsampled in text space, we plot sentence examples from upsampled data.

Figure 5 shows that when seed examples are upsampled to , DeltaS cluster moves closer to the seed examples, and while most of the DeltaR generated data forms a separate cluster, a few of the generated examples are close to the seed examples. Since, in experiments with upsampled text examples, DeltaR performs better than other FDA methods, we hypothesize that DeltaR increases the amount of variability within the dataset by generating diverse examples which leads to a more robust model.

6 Conclusion and Future Work

In this paper, we investigate six FDA methods including Upsample, Perturb, CVAE, Delta-Encoder, Extra, and Linear to augment training data. We show that FDA works better when combined with transfer learning and provides an effective way of bootstrapping an intent classifier for new classes. As expected, all FDA methods become less effective when the number of seed examples increases and provides minor gains in the full-data regime. Through comparing methods on two public datasets, our results show that Linear is a competitive baseline for FDA in FSI setting, especially when combined with transfer learning (BERT).

Additionally, we provide empirical evidence that in few-shot integration setting, feature space augmentation combined with BERT provides better performance than widely used text space upsampling. Given that pre-trained language models provide state of the art performance on several NLP tasks, we find this result to be in particular encouraging, as it shows potential for applying FDA methods to other NLP tasks.

Our experiments on Delta-Encoder also shows that unlike few-shot image classification, Delta-Encoder fails to learn transferable intra-class variations. This result emphasizes that methods providing improvements in computer vision domain might not produce similar gains on NLP tasks, thus underlining the need to develop data augmentation methods specific to NLP tasks.


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Appendix A FSI experiment results for all intents

In all tables, individual columns represent FSI results for an intent, and Overall Mean column, provides average accuracy for all intents’ FSI simulations.

# Method Playlist Restaurant Weather Music Book Work Event Overall Mean
No Augmentation 82.63(5.11) 87.86(3.53) 84.51(1.3) 88.07(2.37) 96.81(2.94) 85.14(1.53) 87.19(3.31) 87.46(2.87)
100 Upsample 92.24(2.96) 97.7(0.67) 96.44(0.75) 94.57(1.1) 97.96(0.82) 89.61(3.01) 91.26(2.35) 94.26(1.66)
Perturb 93.09(2.55) 97.41(0.92) 96.07(1.35) 94.39(1.13) 97.86(0.93) 89.36(2.76) 91.09(2.53) 94.18(1.74)
CVAE 92.4(3.66) 97.47(0.67) 96.49(1.07) 94.36(1.26) 97.71(1.1) 89.1(2.79) 91.2(2.22) 94.1(1.83)
Linear 92.61(3.02) 97.74(0.67) 96.44(0.77) 94.63(1.18) 97.97(0.78) 89.61(3.05) 91.53(2.34) 94.36(1.69)
Extra 92.36(3.0) 97.74(0.66) 96.41(0.77) 94.6(1.18) 97.97(0.78) 89.47(3.11) 91.51(2.3) 94.3(1.68)
DeltaR 87.07(4.67) 93.57(4.07) 91.0(4.23) 94.87(1.28) 97.66(1.42) 85.97(2.34) 89.11(3.84) 91.32(3.12)
DeltaS 92.64(4.49) 97.76(0.7) 96.41(1.25) 94.99(0.92) 97.83(0.99) 88.69(2.69) 91.64(2.36) 94.28(1.92)
512 Upsample 95.3(1.09) 98.0(0.64) 97.63(0.34) 95.57(0.87) 98.03(0.55) 92.0(1.49) 93.26(1.05) 95.68(0.86)
Perturb 95.33(1.2) 97.94(0.6) 97.6(0.44) 95.5(0.91) 97.91(0.55) 92.03(1.78) 93.21(0.99) 95.65(0.92)
CVAE 95.46(1.12) 97.89(0.62) 97.54(0.43) 95.36(1.02) 97.93(0.7) 91.34(2.17) 92.73(1.19) 95.46(1.03)
Linear 95.39(1.1) 98.0(0.64) 97.67(0.36) 95.74(0.89) 98.04(0.5) 92.61(1.47) 93.66(1.13) 95.87(0.87)
Extra 95.36(1.17) 98.0(0.64) 97.66(0.37) 95.74(0.88) 98.04(0.5) 92.29(1.52) 93.63(1.17) 95.82(0.89)
DeltaR 95.36(1.74) 97.81(0.69) 97.6(0.44) 95.9(0.97) 97.74(1.02) 90.27(3.44) 92.61(2.64) 95.33(1.56)
DeltaS 95.66(1.18) 97.96(0.59) 97.8(0.45) 95.91(0.88) 97.91(0.74) 92.26(2.57) 93.66(0.86) 95.88(1.04)
Table 5: IC accuracy on SNIPS dataset in the FSI setting (), reported as mean (SD).
# Method Directions Distance Arrival Duration Traffic Event Overall Mean
No Augmentation 89.61(0.1) 89.94(0.09) 90.56(0.12) 81.74(0.13) 68.5(0.13) 67.39(0.11) 81.29(0.11)
100 Upsample 89.89(0.27) 93.64(0.87) 92.95(0.57) 84.28(3.45) 68.99(0.49) 76.26(5.41) 84.34(1.84)
Perturb 89.82(0.24) 93.58(0.84) 92.81(0.55) 84.81(3.77) 69.15(0.68) 74.07(5.6) 84.04(1.95)
CVAE 89.91(0.32) 93.46(0.77) 92.7(0.67) 84.45(3.52) 69.11(0.9) 74.94(5.49) 84.1(1.94)
Linear 89.93(0.24) 93.65(0.88) 92.98(0.57) 84.2(3.44) 68.96(0.51) 76.12(5.77) 84.31(1.9)
Extra 89.88(0.27) 93.61(0.89) 92.96(0.59) 84.21(3.43) 68.94(0.46) 75.18(5.34) 84.13(1.83)
DeltaR 89.64(0.11) 92.57(1.3) 90.79(0.37) 81.72(0.12) 68.48(0.08) 68.63(2.59) 81.97(0.76)
DeltaS 89.88(0.34) 93.68(0.72) 92.6(0.76) 83.88(3.2) 68.93(0.67) 72.05(5.83) 83.5(1.92)
512 Upsample 91.93(0.48) 94.58(0.34) 93.99(0.31) 92.56(0.72) 75.84(2.19) 85.27(1.87) 89.03(0.99)
Perturb 91.78(0.49) 94.58(0.43) 94.02(0.25) 92.53(0.87) 76.0(2.27) 85.22(1.61) 89.02(0.99)
CVAE 91.85(0.52) 94.57(0.39) 94.0(0.34) 92.45(0.92) 74.91(2.73) 84.5(1.61) 88.71(1.09)
Linear 92.14(0.66) 94.6(0.35) 94.05(0.32) 92.78(0.67) 76.0(2.49) 86.22(1.7) 89.3(1.03)
Extra 92.11(0.57) 94.61(0.35) 94.04(0.29) 92.72(0.7) 75.79(2.45) 85.98(1.58) 89.21(0.99)
DeltaR 90.43(0.55) 94.54(0.35) 93.8(0.3) 86.64(4.38) 71.68(1.46) 86.55(1.75) 87.28(1.46)
DeltaS 91.83(0.47) 94.66(0.4) 94.08(0.24) 92.31(1.45) 75.81(2.1) 86.23(2.08) 89.15(1.12)
Table 6: IC accuracy on FBDialog dataset in the FSI setting (), reported as mean (SD).
# Method Playlist Restaurant Weather Music Book Work Event Overall Mean
No Augmentation 96.0(1.69) 95.39(1.59) 96.41(1.18) 93.1(1.38) 97.79(0.77) 88.46(1.14) 93.49(0.87) 94.38(1.23)
100 Upsample 96.0(1.57) 95.87(1.26) 96.51(1.04) 93.19(1.25) 97.83(0.7) 88.63(1.21) 93.7(0.83) 94.53(1.12)
Perturb 96.1(1.64) 95.7(1.23) 96.43(1.28) 93.33(1.1) 97.8(0.77) 88.56(1.32) 93.7(0.9) 94.52(1.18)
CVAE 96.07(1.46) 95.91(1.43) 96.43(1.31) 93.2(1.15) 97.83(0.78) 88.63(1.28) 93.66(0.86) 94.53(1.18)
Linear 96.0(1.57) 95.89(1.26) 96.51(1.04) 93.19(1.25) 97.83(0.7) 88.63(1.21) 93.7(0.83) 94.53(1.12)
Extra 96.0(1.57) 95.84(1.3) 96.51 (1.04) 93.19(1.25) 97.83(0.7) 88.63(1.21) 93.7(0.83) 94.53(1.13)
DeltaR 96.09(1.51) 95.74(1.46) 96.44(1.29) 93.56(0.95) 97.86(0.75) 88.79(1.25) 93.86(0.93) 94.62(1.16)
DeltaS 96.11(1.52) 95.69(1.44) 96.46(1.29) 93.44(0.93) 97.86(0.75) 88.64(1.18) 93.76(0.89) 94.57(1.14)
512 Upsample 96.07(1.54) 96.09(1.2) 96.6(1.06) 93.5(1.14) 97.87(0.69) 88.73(1.23) 93.8(0.92) 94.67(1.11)
Perturb 96.23(1.6) 96.17(1.23) 96.63(1.13) 93.49(1.03) 97.84(0.72) 88.6(1.3) 93.79(0.98) 94.68(1.14)
CVAE 96.14(1.46) 96.24(1.18) 96.63(1.06) 93.6(1.08) 97.87(0.75) 88.76(1.29) 93.87(0.98) 94.73(1.11)
Linear 96.07(1.54) 96.11(1.21) 96.6(1.06) 93.49(1.13) 97.87(0.69) 88.76(1.25) 93.8(0.92) 94.67(1.11)
Extra 96.07(1.54) 96.13(1.18) 96.6(1.06) 93.5(1.14) 97.87(0.69) 88.73(1.25) 93.8(0.92) 94.67(1.11)
DeltaR 96.29(1.52) 96.29(1.34) 96.71(1.1) 93.87(1.04) 97.86(0.75) 89.11(1.22) 94.03(0.89) 94.88(1.12)
DeltaS 96.19(1.61) 96.2(1.23) 96.69(1.07) 93.61(0.96) 97.86(0.75) 88.84(1.28) 93.83(0.94) 94.74(1.12)
Table 7: IC accuracy on SNIPS dataset in the FSI setting, reported as mean (SD). The seed examples are upsampled to to train the feature extractor.