Mastering Opinion Summarization with GPT: Exploring Pipeline Methods, Evaluation Metrics, and Expert Insights

Matt Payne
August 21, 2023

GPT-4, the fourth iteration of the Generative Pre-trained Transformer, is a cutting-edge language model that has exhibited exceptional performance across a broad spectrum of natural language processing tasks. With an unprecedented size and conversational ability, GPT-4 has demonstrated remarkable capabilities in a zero shot setting for various applications, including text generation, translation, question-answering, and summarization. Its ability to perform tasks with minimal or no fine-tuning has garnered significant attention in the artificial intelligence community, highlighting its potential in diverse domains and use-cases.

Opinion summarization is a critical task in the realm of natural language processing, particularly in the context of user reviews for products or services. The primary objective of opinion summarization is to extract and condense valuable insights from large volumes of text, enabling businesses, customers, and decision-makers to comprehend the prevailing sentiment and essential information contained within these reviews. By generating accurate and coherent opinion summaries, stakeholders can gain a clearer understanding of users' experiences, preferences, and concerns, ultimately informing strategic decisions and improvements that cater to users' needs. Despite GPT-4's impressive performance in various tasks, employing it for long-form opinion summarization presents several challenges. One of the primary hurdles is the model's struggles with leveraging few shot examples, which complicates the application of GPT-4 to summarize data in a specific tone or voice. Additionally, GPT-4 may generate summaries that merely echo the inputs or exhibit an imbalance in representing contradictory opinions, particularly when faced with a diverse set of viewpoints. These challenges underscore the need for developing techniques that can effectively harness GPT-4's capabilities for long-form opinion summarization while maintaining faithfulness, factuality, and avoiding generic outputs.

To tackle these issues, we explore various pipeline methods aimed at enhancing GPT-4's applicability in the context of long-form opinion summarization. The methods investigated include recursive summarization, which involves summarizing text iteratively, and content selection through supervised clustering or extraction, which focuses on identifying and selecting salient content for summarization. By examining these approaches, this paper and an original research paper on GPT-3 aims to provide a more comprehensive understanding of GPT43's strengths and limitations in generating summaries that accurately and coherently represent user opinions. Furthermore, this study critically evaluates the effectiveness of standard evaluation metrics, such as ROUGE and BERTScore, in assessing the quality of GPT generated summaries. Recognizing the limitations of these metrics, the study also walks through a set of entailment-based metrics designed to measure factuality, faithfulness, and genericity in the produced summaries. These metrics leverage natural language inference models to estimate the extent of overgeneralization, misrepresentation, and genericness in summaries, providing a more nuanced evaluation of GPT-4's performance in the opinion summarization task.

Through this in-depth investigation, the paper and our reviewers contribute to a deeper understanding of GPT's potential and limitations in long-form opinion summarization, as well as offer insights into effective strategies for improving the model's performance in this context. The findings and proposed evaluation metrics can serve as a valuable resource for businesses aiming to harness GPT-4 for opinion summarization tasks and guide the development of future language models that better address the challenges presented by long-form inputs and diverse viewpoints. Let’s walk through our deep look at how we can use GPT-4 for opinion summarization based on the original work done for older models done here (Bhaskar Nov. 2022).

Background of Related Summarization Methods

Review summarization is a subdomain of natural language processing that focuses on condensing and synthesizing large collections of user-generated reviews into a concise and meaningful summary. This process aims to help stakeholders, such as businesses, potential customers, and decision-makers, comprehend the overall sentiment, key themes, and significant information embedded within these reviews. By distilling the wealth of information contained in user reviews, review summarization enables users to quickly grasp the key insights, strengths, and weaknesses of a product or service without having to read through vast amounts of text. Traditionally, review summarization techniques have been categorized into two primary approaches: extractive and abstractive summarization. Extractive summarization methods involve selecting the most relevant and informative sentences or phrases from the original reviews and assembling them into a coherent summary. Early works in this area relied on sentence extraction, topic modeling, or clustering to identify and select the representative content from the input reviews.

On the other hand, abstractive summarization methods focus on generating novel sentences that capture the essence of the input reviews, often rephrasing and combining information from multiple sources to create a more succinct and coherent summary. Although historically less prevalent than extractive approaches, abstractive summarization has gained significant attention in recent years, particularly with the advent of powerful pre-trained language models like GPT-3. These models have demonstrated superior capabilities in generating fluent, coherent, and contextually relevant summaries by leveraging their vast knowledge base and advanced natural language understanding. In addition to extractive and abstractive methods, several hybrid techniques have also emerged, combining the strengths of both approaches to generate more accurate, informative, and representative summaries. For instance, multi-stage approaches, which involve extracting relevant content from the input reviews followed by abstractive summarization of the extracted information, have shown promise in tackling long documents and addressing the challenges presented by diverse viewpoints. We’ve also seen a rise of blended summarization as a way for use cases such as legal document summarization to extract more insights out of the same summarization model.

Despite the advances in review summarization techniques, several challenges remain, particularly in terms of generating summaries that faithfully represent the input reviews, maintaining factuality, and avoiding overly generic outputs. As the use of pre-trained large language models like GPT becomes more prevalent in the field of review summarization, it becomes increasingly important to develop strategies and evaluation metrics that can help researchers and practitioners effectively harness these models to address these challenges and generate high-quality, informative, and accurate summaries of user opinions.

Extractors and Summarizers: Harnessing GPT for Opinion Summarization

To tackle the challenges of applying GPT-4 for opinion summarization, we have deployed various extractors and summarizers that form the basis of their pipeline methods. These components are designed to process long-form inputs, select salient content, and generate accurate, coherent, and concise summaries of user opinions. Let's dive into each of these components and explore how they contribute to the overall summarization process.


Extractors are responsible for selecting the most relevant parts of a set of reviews, often conditioned on specific aspects. The researchers have developed several extractors that can be applied in their pipelines:

1. **GPT-4 Zero Shot Topic Clustering** This extractor leverages GPT-4's capabilities to perform topic prediction and clustering for each sentence within the input text. First, every sentence is passed to GPT-4 with a prompt to generate a single word that best represents the topic of the given sentence. For example, if a sentence reads, "The room was spacious and had an amazing view," GPT-4 produces the topic word "room."

topic extraction with gpt-4

Next, the generated topic words are mapped to their corresponding aspects by calculating the L2 distance between the GloVe (Pennington et al., 2014) word vectors of the topic words and the predefined aspects. This step ensures that each sentence is associated with the most relevant aspect. In the case of hotel reviews, aspects might include categories such as "rooms," "building," "cleanliness," "location," "service," and "food."

By clustering sentences based on their closest aspects, GPT-4 Topic Clustering forms a selection of sentences that can be used for aspect-oriented summarization. This extractor helps address the challenges of long-form inputs by filtering and organizing content in a way that GPT-4 can more effectively process and summarize. Please note that this step is only used for pipelines on the aspect-oriented summarization dataset, SPACE, which consists of hotel reviews.

To illustrate the GPT-4 Topic Clustering process, let's consider examples from the original GPT-3 research paper. Suppose we have the following sentences extracted from a set of hotel reviews:

1. "The room was spacious and had an amazing view."

2. "The staff were friendly and attentive."

3. "Breakfast options were diverse and tasty."

When these sentences are passed to GPT-4 for zero shot topic prediction, the model produces these outputs.

zero shot topic prediction

Using the GloVe word vectors, these topic words are then mapped to the closest aspects. These clustered sentences can now be used as input for aspect-oriented summarization using GPT-4.

GloVe architecture
GloVe Word Embeddings (Source)

It is important to note that the GPT-4 Topic Clustering step is specifically designed for the aspect-oriented summarization use case, where the goal is to generate summaries based on specific aspects of the reviews. For datasets that do not have predefined aspects, such as the generic summarization dataset FewSum, this use case does not fit as well.

2. **QFSumm-long**: This extractor employs QFSumm, an aspect-specific extractive summarization model introduced by Ahuja et al. (2022), to extract up to n most relevant sentences from the input text. QFSumm leverages a query-focused approach and is designed to handle extremely long inputs, eliminating the need for truncation at this stage.

In the context of this research, when processing large inputs, n is set to 35 sentences for the "long" variant. QFSumm takes as input the text combined with a set of aspect-related keywords. These keywords are either provided by the dataset or prompted from GPT-4 based on a random selection of five reviews. The keywords serve as queries to guide the extraction of relevant sentences that best represent the input's aspects.

For example, in the case of hotel reviews, if the aspect being summarized is "cleanliness," QFSumm uses the associated keywords to identify the most relevant sentences from the input text that pertain to cleanliness. The sentences selected by QFSumm are then used as input for the subsequent summarization step using GPT-4.

By employing QFSumm-long in the pipeline, the researchers were able to effectively filter and condense the input content, allowing GPT-4 to focus on a smaller, more relevant subset of sentences for summarization. This approach addresses the challenges of long-form inputs and facilitates the generation of more accurate, coherent, and concise summaries that align with the target aspects.

3. **Review Stratification**: This approach involves a more sophisticated technique for handling the input reviews by taking into account the scores provided by the reviewers. The main idea behind review stratification is to group reviews based on their scores and then summarize each group separately using GPT-4. The motivation for this method is to capture and represent diverse viewpoints present in the reviews, highlighting both positive and negative aspects of the product or service.

To implement review stratification, the researchers first cluster the reviews based on the reviewer's scores, which are available in the dataset. These scores can range from 1 (lowest) to 5 (highest), resulting in five distinct clusters of reviews. For each cluster, the researchers apply GPT-3 summarization to generate a summary that captures the overall sentiment and key points of the reviews within that specific cluster.

However, in cases where a cluster's length exceeds GPT's maximum input length limit, researchers introduced a truncation step to ensure that the input size remains within the admissible range for GPT. This truncation step involves selecting the largest number of sentences that fit within GPT's maximum input length limit, ensuring that the input remains manageable for the model while preserving as much information as possible from the original reviews .

To illustrate the review stratification process, let's consider an example from the research paper. Suppose we have a set of hotel reviews with varying scores:

1. "The room was spacious and had an amazing view. (Score: 5)"

2. "The staff were friendly and attentive. (Score: 4)"

3. "The hotel was quite noisy at night. (Score: 2)"

In this example, review stratification would first cluster the reviews based on their scores:

- Cluster 1 (Score: 5): "The room was spacious and had an amazing view."

- Cluster 2 (Score: 4): "The staff were friendly and attentive."

- Cluster 3 (Score: 2): "The hotel was quite noisy at night."

Next, GPT-3 is applied to generate a summary for each cluster:

- Cluster 1 summary: "Guests loved the spacious rooms with amazing views."

- Cluster 2 summary: "Service was praised for its friendliness and attentiveness."

- Cluster 3 summary: "Some guests experienced noise disturbances during their stay."

By summarizing each cluster separately, review stratification ensures that diverse opinions and viewpoints are represented in the final summaries, providing a more accurate and balanced representation of the user experiences. The resulting summaries can then be combined or presented separately to convey a comprehensive understanding of the various aspects of the product or service, as highlighted by the reviewers. This approach offers a more in-depth insight into the different perspectives present in the reviews, which can be valuable for both potential customers and businesses seeking to improve their offerings.

In addition to these extractors, the researchers also employ GPT-3 chunking in their pipelines. This process involves dividing the sentences from the prior step into non-overlapping chunks, which are then summarized individually by GPT-3. The results are concatenated for the next step.

Summarizers: The Final Touch in GPT-4 Opinion Summarization

In the previous section, we discussed how extractors play a vital role in selecting relevant content from long-form inputs for opinion summarization. However, the final step in generating accurate, coherent, and concise summaries lies in the hands of summarizers. In this section we'll dive into the different types of summarizers used in these experiments and explore how they contribute to the overall summarization process, with some illustrative examples.

GPT-4: The Star of the Show

The primary summarizer used in this outline is GPT-4 itself. Given its exceptional natural language processing capabilities and remarkable performance in various zero shot tasks, it's no surprise that GPT-4 takes center stage in the summarization pipelines.

Our full GPT Zero Shot Summarization Pipeline

We’ve been huge fans of GPT as a summarization model for a long time, with supporting writing such as SOTA GPT-3 Summarization, Blended Summarization, News Summarization, and more. The ability to reach summaries that are overwhelmingly preferred by human evaluators even in low data environments like zero shot prompts is truly game changing. On top of the accuracy seen with GPT summarizers, the quick iterations you can make with the simple prompt requirement allows you to tailor summaries exactly to your use case without needing a massive dataset of examples or transfer learning from a data set that isn’t quite right for the golden summary you have in mind.

When using GPT-4 as a summarizer, we provide it with a carefully crafted prompt that guides the model to generate the desired opinion summary. For instance, when summarizing hotel reviews, GPT-4 is prompted with an instruction statement like "Summarize what the reviewers said about the rooms:". The header used in the prompt can also vary depending on whether GPT-4 chunking was used in the pipeline or not. For example, the header might read, "Here's what some reviewers said about a hotel:" or "Here are some accounts of what some reviewers said about the hotel." The goal of this is to leverage early prompt token bias to provide the model with a bit of in-context knowledge about what the goal output is for your summary. The key with summarization is always to steer the model towards what you believe is a correct summary, not what it believes it is based on task agnostic pretraining. All of our prompts use a header, prompt variables, and instructions.

By tweaking the prompt instructions and headers, we ensure that GPT-3 produces high-quality summaries that capture the essence of the input reviews and align with the target aspects.

To illustrate GPT-4's summarization capabilities, let's take a look at a few examples.

reviewers summary of hotels

Here are five long reviews for various hotels. You can see we use a simple header in the System section and a pretty standard instruction. The summary comes out abstractive but does a great job of mentioning specific ideas that lead to the opinions.

structured reviews of hotels

Here’s a summary that better fits how we like to structure our outputs. These instructions have a clearly defined task (summarization in one sentence) and a clearly defined goal output. In zero shot settings it’s critical to leverage your instructions to help steer the model. Since you don’t have prompt examples to help the model understand how to generate a summary for your use case, this prompt instructions template is what is required.

summary output for hotels

Be careful when trying various output formats such as bulleted lists. This can lead to the model not working through the task in the same way as before. Now we can see it generates a bullet for each review instead of a single summary for all reviews, because normally providing an input list of data and asking for bullets means you don’t want to combine it into a single summary. This new output format would require us to tweak instructions to ensure it's a combined summary.

QFSumm for Fine-Tuned Extractive Summarization

The authors of the original research paper also explore the use of QFSumm as a standalone summarizer. QFSumm, introduced by Ahuja et al. (2022), is an extractive summarization model specifically designed for handling long-form inputs. It works by selecting a predetermined number of the most relevant sentences from the input text, effectively creating a shorter summary. For this comparison, the default setting for QFSumm is set to extract only three sentences. However, it's important to note that QFSumm is primarily an extractive summarization model, meaning that it does not generate new sentences or rephrase the original text. Consequently, QFSumm's summaries may lack the fluency and coherence that GPT-4's abstractive summaries can offer. It is still preferred to use GPT-4 for extractive summarization in many use cases as we’ve outlined in articles like our news summarization review.


Another summarization model worth reviewing is AceSum, developed by Amplayo et al. (2021a). Like GPT, AceSum is an abstractive summarization model that generates new sentences to create coherent and concise summaries. However, unlike GPT, AceSum does not offer a way to control the length of the output summary, which makes it less suitable for use within a pipeline. In the original research paper, AceSum is used as a standalone model for comparison purposes, showcasing the effectiveness of the proposed GPT-3-based pipelines in generating high-quality summaries. The fact that AceSum is mentioned alongside GPT-3 and QFSumm demonstrates the variety of summarization models available and highlights the importance of selecting the right model for a given task.

Here are some quick results of the three different models when summarizing hotel reviews against golden summaries. We’ll compare the results of these different pipelines using popular datasets in the evaluation section.
Here are some quick results of the three different models when summarizing hotel reviews against golden summaries. We’ll compare the results of these different pipelines using popular datasets in the evaluation section.

Datasets for Opinion Summarization

Stats for the datasets. (source)
Stats for the datasets. (source)

Two primary datasets are worth using to evaluate the effectiveness of the proposed GPT based pipelines for opinion summarization. Let's take a quick look at these datasets and their characteristics.

1. SPACE (Amplayo et al., 2021a)

SPACE is an aspect-oriented summarization dataset focused on hotel reviews. It consists of reviews categorized into seven aspects: general, rooms, building, cleanliness, location, service, and food. For each hotel and aspect pair, the dataset provides three human-written summaries. The SPACE dataset presents a challenging environment for prompt based models, as the combined length of the reviews often exceeds the maximum input length of GPT-3, and still causes issues in the zero shot environment of GPT-4. This dataset is particularly useful for evaluating the performance of the GPT based pipelines in handling long-form inputs and generating summaries that accurately represent the users' opinions on specific aspects of the hotels.

2. FewSum (Bražinskas et al., 2020a)

FewSum is a generic summarization dataset containing product reviews from Amazon and Yelp. Unlike SPACE, FewSum is not aspect-oriented, which means that the summaries generated from this dataset should cover a more general perspective on the products or services reviewed. The reviews in FewSum are typically shorter than those in the SPACE dataset, making it much easier to use in prompt based models where the task is learned on the fly instead of trained. FewSum provides golden summaries for a limited number of products, with 32 and 70 products in the Amazon and Yelp categories, respectively. This dataset allows the researchers to evaluate the GPT-3-based pipelines in a different context, showcasing their versatility and adaptability to various summarization tasks. These datasets, SPACE and FewSum, are perfect for the opinion summarization use case because they represent real-world scenarios where users express their opinions, experiences, and sentiments about products, services, and establishments. Both datasets contain diverse and rich user-generated content in the form of reviews, which often include both positive and negative aspects, making them ideal for evaluating the performance of opinion summarization models. By using both datasets, the researchers can comprehensively evaluate the effectiveness of their GPT based pipelines in generating high-quality summaries that accurately represent diverse user opinions in various contexts and domains, making them well-suited for the opinion summarization use case. Additionally, the varying lengths of the reviews in these datasets allow the researchers to test and refine their pipeline methods to handle the challenges of long-form inputs, further strengthening their applicability to real-world opinion summarization tasks. Overall, these datasets provide an ideal testing ground to develop, evaluate, and optimize the GPT based pipelines for opinion summarization.

Evaluating Opinion Summarization: A Closer Look at Old School Metrics

In the world of text summarization, it's crucial to evaluate the effectiveness of the generated summaries. One ways engineers have always evaluated summarization systems is the use of two popular evaluation metrics, ROUGE and BERTScore. It’s worth noting that old school evaluation metrics like ROUGE and BERTScore have been proven to be poor representations of how quality a summary is to actual human reviewers. These metrics focus on information in generated summaries that does map well to an understanding of what information matters in a summary, especially in abstractive summarization use cases. We looked at this in our new summarization blog post that compared these metrics to human evaluations. While the old school metrics preferred fine-tuned models, human evaluators clearly preferred summaries generated by GPT. Considering how popular these old school metrics still are in summarization and natural language generation today, it's worth reviewing them.

Summary reviewers preferred summaries from GPT, BRIO, and T0. GPT was clearly preferred as the best summary on both datasets that were used. (source)
Summary reviewers preferred summaries from GPT, BRIO, and T0. GPT was clearly preferred as the best summary on both datasets that were used. (source)

More results from reviewers of news summaries. They even preferred GPT-3 before GPT-4 came out! (source)

ROUGE: A Classic Metric for Summarization

ROUGE (Recall-Oriented Understudy for Gisting Evaluation) is a widely used evaluation metric in the field of text summarization. Developed by Lin (2004), ROUGE measures the quality of a generated summary by comparing it to one or more reference summaries, typically created by humans. The metric focuses on n-gram overlap (part of the reason it fails at abstractive summarization review) between the generated and reference summaries, with higher scores indicating a better match and, by implication, a higher-quality summary. In the original research paper, the authors computed ROUGE scores for the various GPT based pipelines, as well as AceSum and QFSumm, to compare their performance. While AceSum achieved the highest ROUGE-1 and ROUGE-L scores, QFSumm lagged behind the other pipelines, particularly in the SPACE dataset. On the FewSum dataset, the GPT systems performed slightly better than QFSumm on the Yelp split, attributed to the smaller combined per-product review lengths of Yelp.

model comparison
Topic-wise clustering + GPT (TCG), GPT (G), Chunking + GPT (CG), QFSumm + GPT (QG), QFSumm (Q), AceSum (A), Topic-wise + QSumm + GPT (TQG), Review Stratification + GPT (RG)

Even the original researchers argued that ROUGE scores may not be the most informative evaluation in this context. As the fluency and coherence of the generated summaries increase to near-human levels, ROUGE's n-gram matching approach can penalize prompt based LLMs for generating summaries in slightly different styles, even if they convey the same information (exactly what we thought above!). Moreover, the actual mistakes made by the GPT based pipelines, such as over-generalization and misrepresentation of viewpoints, are not well captured by ROUGE scores.

BERTScore: A More Sophisticated Approach

bertscore architecture
BERTScore (source)

To complement ROUGE and provide a more comprehensive evaluation, the researchers also used BERTScore, a metric proposed by Zhang et al. (2020b). BERTScore leverages the power of pre-trained language models like BERT to measure the similarity between generated and reference summaries at the contextual level, rather than just relying on n-gram overlap. This is a similar approach to the ideas that came out of this research that we use to show customers that human evaluation, or training a model to mimic human evaluation is the best approach to natural language generation. The authors found that the BERTScores for AceSum and all GPT related models were in the range of 88-90, with QFSumm falling behind on the SPACE dataset. However, the differences in performance between the models were not as clear as with ROUGE scores, making it difficult to draw definitive conclusions. While BERTScore offers a more sophisticated approach to evaluating summary quality, it still has limitations when it comes to assessing the finer nuances of opinion summarization. For instance, it may not adequately capture errors related to overgeneralization, misrepresentation of viewpoints, or the balance of contradictory opinions, which are crucial aspects to consider in opinion summarization. Now that we’ve got that out of the way we can focus on the best way to evaluate summaries, human evaluation.

Human Evaluation: Putting Summarization Models to the Ultimate Test

In the quest for developing accurate and effective opinion summarization models, it's crucial to assess their performance from a perspective that does not have clearly defined math metrics. After all, the end-users of these summaries are human beings who expect coherent, factual, and relevant information.

The Evaluation Process

cool opinion true negative results
Interesting finding with zero shot GPT-4 opinion summarization. The model understands that reviews are not related to opinions of rooms. Not only that but it creates a summarization of the key ideas discussed in the reviews. By refining the prompt used for summarization you are also shrinking the data variance available to the model.

The human evaluation process involved assessing the summaries generated by the GPT based pipelines along with those produced by AceSum and QFSumm for a set of randomly chosen items from both the SPACE and FewSum datasets. We can look at four key axes that reviewers can use to determine the quality of opinion summarization review:

1. Intrinsic Factuality: One of the key aspects evaluated on is Intrinsic Factuality, which measures how accurately the summary represents the popularity of the opinions expressed in the source text. Intrinsic Factuality focuses on whether the summary correctly portrays the balance of opinions and their respective prominence. For example, if the majority of the reviews praise the cleanliness of a hotel, the summary should reflect this positive sentiment as the dominant viewpoint. On the other hand, if only a small fraction of reviewers express dissatisfaction with the cleanliness, the summary should not overstate the importance of this minority opinion.

Zero shot GPT-4 often covers intrinsic factuality by saying “several” or “some reviewers” to keep from making claims about the reviews as a whole
Zero shot GPT-4 often covers intrinsic factuality by saying “several” or “some reviewers” to keep from making claims about the reviews as a whole

An inaccurate representation of Intrinsic Factuality might occur if the summary states that "Some people said the hotel was clean, while others said it was dirty," when in reality, the vast majority of reviewers praised the cleanliness, and only a few had negative comments. In this case, the summary would inaccurately suggest that the opinions are evenly divided, which could mislead the reader. The authors of the research paper independently rated the summaries generated by the different pipelines along the Intrinsic Factuality axis using a Likert scale of 1-3, with higher scores indicating better accuracy in representing the popularity of opinions. The average scores and inter-rater agreement values were then calculated to compare the performance of the models. The human evaluation results showed that all models, including the GPT based pipelines, AceSum, and QFSumm, achieved relatively high scores in Intrinsic Factuality. This suggests that the models were generally successful in accurately representing the popularity of opinions in the input reviews. However, the differences in scores among the models were small, indicating that there is still room for improvement in capturing the nuances of opinion popularity.

Results of human evaluation in the original research paper with our 4 key areas on the two datasets.
Results of human evaluation in the original research paper with our 4 key areas on the two datasets.

2. Extrinsic Factuality: An Overview

Extrinsic Factuality assesses whether all the statements made in a summary are supported by the input text. In other words, it evaluates if the summary contains any claims or assertions that cannot be traced back to the original input, such as user reviews. A great example of this would be accounting for a single negative review such as “the hotel is very expensive” in a summary when the rest of the reviews are positive. Opinion summarization models should ideally generate summaries that accurately represent the views and opinions expressed in the source text without introducing any incorrect or unsupported information. A high score in Extrinsic Factuality indicates that the summarization model is successful in capturing accurate information from the input and generating summaries that stay true to the original content.

Assessing Extrinsic Factuality

GPT-4 does a great job at avoiding hallucinations and making it very easy to trace specific summary points to information in the reviews. This is partially due to the abstract nature of the bullet summaries which makes it an easier job for GPT-4.
GPT-4 does a great job at avoiding hallucinations and making it very easy to trace specific summary points to information in the reviews. This is partially due to the abstract nature of the bullet summaries which makes it an easier job for GPT-4.  

To evaluate the performance of the GPT based pipelines and alternative models (AceSum and QFSumm) on Extrinsic Factuality, the authors conducted a human evaluation, rating the summaries along this dimension using a Likert scale of 1-3. The results revealed that GPT based pipelines, AceSum, and QFSumm all achieved high scores in Extrinsic Factuality. This suggests that these models are effective in generating summaries that avoid introducing unsupported or counterfactual statements. The absence of blatantly false information in the summaries indicates that these models can be trusted to produce summaries that adhere to the original input text. However, it's important to note that a high score in Extrinsic Factuality does not necessarily guarantee that the generated summaries are also accurate in terms of Intrinsic Factuality or Faithfulness. Intrinsic Factuality focuses on the accuracy of the summary in representing the popularity of opinions, while Faithfulness assesses the appropriateness of the viewpoints selected in the summary. Therefore, it is essential to evaluate the performance of opinion summarization models across all these dimensions to gain a comprehensive understanding of their effectiveness.

Extrinsic Factuality is a crucial aspect to consider when evaluating the performance of opinion summarization models, as it ensures that the generated summaries contain accurate information that can be traced back to the source text. The research paper demonstrates that the GPT based pipelines and alternative models generally perform well in this regard, showcasing their ability to generate summaries that stay true to the original content. However, as mentioned earlier, it is important to evaluate the models across multiple dimensions, such as Intrinsic Factuality and Faithfulness, to ensure the development of high-quality summarization systems that accurately represent diverse user opinions in a coherent and relevant manner.

3. Faithfulness: The accuracy of the viewpoints selected in the summary, ensuring they represent the consensus opinions.

4. Relevance: The degree to which the points raised in the summary are relevant to the aspect being summarized.

Insights from Human Evaluation

The human evaluation results revealed several interesting insights into the performance of the GPT-3-based pipelines and alternative models. Some key takeaways include:

- Among the GPT based pipelines, the TCG pipeline (Topic Clustering + GPT-3) significantly improved relevance scores compared to other pipelines. - All models, including GPT-3-based pipelines, AceSum, and QFSumm, achieved high scores in extrinsic factuality, suggesting that they rarely generate blatantly counterfactual statements. This is great news for GPT as GPT-4 has already been proven to produce more factually accurate answers then previous models, and have a better understanding of times where it might not have the best answer.

- QFSumm's summaries were generally faithful and factual due to their extractive nature but sometimes included statements not relevant to the aspect being summarized.

- Overall, the AceSum model and TCG pipeline performed better than other pipelines, although differences in factuality and faithfulness scores were relatively small.

Evaluation Moving Forward

Human evaluation clearly plays a crucial role in assessing the performance of opinion summarization models, offering a more nuanced and accurate perspective on their strengths and limitations. By incorporating human evaluation into your evaluation pipelines, you’re able to gain a more realistic view of how users view your summaries. Even if in some use cases the results are similar to that of metric based evaluations it’s clear that someone as abstract as opinion based summarization. As the field continues to evolve, it's essential for practitioners to embrace a diverse set of evaluation methods, including human judgment, to ensure the development of high-quality summarization systems that meet end-user expectations. By doing so, we can work towards creating more accurate, coherent, and relevant summaries that effectively represent diverse user opinions, ultimately benefiting both businesses and consumers in making well-informed decisions.

Exploring New Evaluation Tools for Opinion Summarization

In the research paper we've been discussing, the authors recognize the limitations of existing evaluation metrics like ROUGE and BERTScore in capturing the nuances of opinion summarization. To address this challenge, they propose a set of new tools for evaluation and analysis, focusing on aspects such as faithfulness, factuality, and genericity. In this blog post, we'll dive deep into these novel evaluation methods and discuss how they contribute to a more comprehensive understanding of summarization model performance. Let’s take a look at a number of different ways to quantify the human evaluation process to give users a bit more structure to best look at summaries and understand how to evaluate at scale based on the methods outlined in the original research paper. We’ve integrated many of these into our workflows to provide better feedback on summaries.

Entailment-Based Metrics: A Valuable Approach for Evaluating Opinion Summarization

When it comes to opinion summarization, the ability to accurately represent diverse and sometimes contradictory user opinions is crucial. One of the key challenges faced by summarization models is striking the right balance between faithfulness to the input reviews and factuality of the generated summaries. To address this challenge, we can use an entailment-based approach for evaluating faithfulness and factuality, which offers several valuable benefits for opinion summarization.

Capturing Consensus and Diverse Viewpoints

Entailment-based metrics measure the degree to which a generated summary accurately represents the consensus opinions found within the input reviews. By using this approach, researchers can assess how well a summarization model captures popular viewpoints and the overall sentiment of the users. This is particularly important in opinion summarization, where the goal is to condense a large collection of user reviews into a concise summary that captures the essence of the users' opinions.

We can prompt language models to generate entailment information at a per sentence level and leverage the SummaC (Laben et al., 2022) approach to compute the scores.

Moreover, entailment-based metrics can help identify cases where the summarization model misrepresents or overgeneralizes the viewpoints expressed in the input reviews. This can be particularly valuable for detecting issues such as the inclusion of irrelevant or unsupported statements in the summary, which can negatively impact the overall quality and usefulness of the generated summaries. This is one of the spots where GPT-4 shines the most. These language models are excellent at capturing all sides of the reviews and directly showing the amount the sentiment is shown through words like “most customers” or “some reviewers”. These models often effortlessly combine sentiment analysis with summarization with simple instructions to put the two together. Here’s an example of a summary that focus on sentiment and key reasons to support the ideas.

great summary of the yelp review dataset with gpt-4

Robustness Against Gaming and Generic Statements

One of the main advantages of using entailment-based metrics for evaluating faithfulness and factuality is their robustness against gaming and the generation of generic statements. Unlike traditional evaluation metrics like ROUGE, which may be susceptible to "gaming" by models that produce "safe" and generic statements, entailment-based metrics can penalize summaries that contain overly general or non-specific value judgments. This is particularly valuable in the context of opinion summarization, where fluency and coherence are often high, and the differences between generated summaries may lie in the subtleties of viewpoint representation and nuance. By using entailment-based metrics, researchers can better assess the quality of the generated summaries in terms of their faithfulness to the input reviews and the accuracy of the represented viewpoints. This is also an extremely useful metric when evaluating language model based summaries, given their intrinsic nature to favor abstractive language. Even in prompts we’ve shown in other articles focused on extractive summarization it's clear to see it’s difficult to drill down. Evaluating these summaries with a focus on how generic they are is one of the best ways to split test prompt language that actually blends extractive nature into generally abstract summaries, all wrapped up in sentiment analysis.  

Flexibility and Adaptability

Another benefit of entailment-based metrics is their flexibility and adaptability. By leveraging Natural Language Inference (NLI) models, these metrics can be applied to a wide range of summarization tasks and domains, making them a versatile tool for evaluating the performance of opinion summarization models across various settings. In conclusion, entailment-based metrics for faithfulness and factuality offer a valuable approach for evaluating opinion summarization models, capturing key aspects such as consensus representation, viewpoint diversity, and robustness against gaming. By incorporating these metrics into their evaluation process, researchers and practitioners can gain a more comprehensive and accurate understanding of model performance, ultimately leading to the development of more effective and accurate opinion summarization systems.

The Value of Semantic and Lexical Genericity in Opinion Summarization

In the research paper we've been discussing, the authors recognize that genericity is an important aspect to consider when evaluating opinion summarization models. A summary that is too generic may not provide the specific insights users are looking for, reducing its usefulness and overall quality. To address this, the researchers introduce two types of genericity—semantic and lexical genericity—to measure the degree of generality in the generated summaries. Semantic genericity refers to making common, non-specific value judgments about a product or service. Identifying and measuring semantic genericity is valuable because it helps ensure that the summary provides meaningful information that distinguishes the product or service from others in the same category. To measure semantic genericity, the researchers use an innovative approach based on entailment scores. A high semantic genericity implies that the summary includes statements that are too general and can apply to many other products or services, reducing the summary's informativeness and value.

On the other hand, lexical genericity involves the use of similar and often overused words in the produced summaries. This type of genericity can make the summary monotonous and less engaging for the reader. By measuring lexical genericity, the researchers can assess how well the summarization models generate diverse and engaging language in their summaries. To measure lexical genericity, the authors employ a TF-IDF-like metric. The Term Frequency-Inverse Document Frequency (TF-IDF) is a popular technique used in information retrieval and natural language processing to weigh the importance of words in a document. In this use case, the researchers calculate an averaged Inverse Document Frequency (IDF) of the summaries, with stopwords removed and stemming applied. The IDF is calculated by dividing the total number of documents (summaries) by the number of documents containing each word, and then taking the logarithm of that quotient. Since generic words are likely to occur more frequently and have a low IDF, a smaller score indicates higher genericity. By using this metric, the researchers can identify which generated summaries overuse common words and phrases, making them less engaging and informative.

In summary, assessing semantic and lexical genericity is valuable for opinion summarization as it helps ensure that generated summaries provide specific, meaningful, and engaging information about the product or service being reviewed. By using innovative approaches like entailment scores and TF-IDF-like metrics, the researchers can gain deeper insights into the performance of their summarization models and identify areas for improvement, ultimately leading to more effective and useful opinion summaries that meet the needs of end-users.

A Data-Driven Comparison of New Tools and Traditional Metrics

The new evaluation tools proposed in the research paper address the limitations of traditional metrics like ROUGE and BERTScore in capturing the nuances of opinion summarization. By focusing on key aspects such as faithfulness, factuality, and genericity, these tools can provide a more accurate and comprehensive assessment of model performance. In this section, we'll take a data-driven approach to explore the value of these new tools for opinion summarization and the results that were found. To assess the effectiveness of the new entailment-based metrics in capturing human judgment, the researchers computed Spearman's Rank Correlation Coefficient between the human-annotated examples and the new metrics. They compared these correlation coefficients with those obtained using ROUGE scores.

entailment based metrics vs rouge

The results showed that the new metrics outperformed ROUGE in terms of correlation with human judgment on both faithfulness and factuality axes. Specifically, the Spearman Correlation Coefficients for the entailment-based metrics were 0.36 for factuality and 0.29 for faithfulness, while the corresponding coefficients for ROUGE were 0.05 and -0.03, respectively. These results highlight that the new metrics are better aligned with human judgment and are more capable of capturing the finer nuances of opinion summarization.

Results of the various pipelines based on entailment
Results of the various pipelines based on entailment

The data-driven comparison of the new tools and traditional metrics reveals several valuable insights for opinion summarization:

1. The new entailment-based metrics are more effective in capturing human judgment, making them better suited for evaluating opinion summarization models in terms of faithfulness and factuality.

2. The traditional metrics, such as ROUGE and BERTScore, may not adequately capture the subtleties of opinion summarization, particularly when it comes to representing diverse and sometimes contradictory opinions.

3. The development of new evaluation tools, such as those proposed in the research paper, can help researchers and practitioners gain a more comprehensive understanding of model performance and identify areas for improvement.

By adopting these new evaluation tools, evaluators can obtain a more accurate and nuanced assessment of opinion summarization models, ultimately leading to the development of more effective and impactful systems. The data-driven comparison of the new tools and traditional metrics underscores the need for continued innovation in evaluation methodologies, paving the way for future advancements in the field of opinion summarization.

The Future of Opinion Summarization Evaluation

The new evaluation tools proposed in the original research paper represent a significant step forward in assessing opinion summarization models more accurately and comprehensively. By combining these novel methods with traditional metrics and human evaluation, researchers and practitioners can gain valuable insights into the strengths and limitations of their GPT-4 models, leading to better and more effective summarization systems. As language models continue to be used as summarization systems the combination of human evaluation and simple machine metrics that mirror the processes of humans will continue to grow. Even though human evaluation metrics are the best route to take for evaluation, they’re not as scalable as traditional approaches, and don’t always provide a quantifiable measure of the results. These newer approaches give us a nice blend of both.

Advancements in Opinion Summarization with GPT

The work done on both GPT-3 and GPT-4 based opinion summarization presents innovative pipeline methods that outperform many old school methods, along with several key findings and contributions that have the potential to shape the future of opinion summarization. These models can be used to create robust summarization pipelines that provide a deeper insight into the information presented in opinions than generic summarization + sentiment analysis pipelines provide.

Want to build your own opinion summarization system?

Width.ai builds custom summarization tools for use cases just like the ones outlined above. We were one of the early leaders in chunk based summarization of long form documents using GPT-3 and have expanded that knowledge to build summarization systems for GPT-4. Let’s schedule a time to talk about the documents you want to summarize!