Sentiment analysis, also referred to as opinion mining, is the use of natural language processing, text analysis, computational linguistics, and biometrics to systematically identify, extract, quantify, and study affective states and subjective information.
In other words, it’s the process of determining the emotional tone or subjective opinion within large amounts of text. This could be used on social media posts, customer reviews, or any other text data where people are expressing their opinions or feelings.
Sentiment analysis can classify text as being positive, negative, or neutral. More advanced sentiment analysis methods can also categorize text into more specific emotional states like “happy,” “frustrated,” “excited,” etc.
Sentiment Analysis Methods
Sentiment analysis methods can be broadly divided into three categories: rule-based, machine learning-based, and hybrid.
This approach uses a set of manually crafted rules to identify sentiment. This often involves creating or using a sentiment lexicon—a list of words and phrases each assigned a sentiment score (positive, negative, or neutral). The overall sentiment of a text is then determined based on the scores of the individual words or phrases it contains. Rule-based methods might also take into account more complex linguistic features, like negations (“not good”) and intensifiers (“very good”).
Machine learning-based methods
These methods involve training a machine learning model on a dataset of text where each piece of text is labeled with its sentiment. The model learns to associate features of the text (like the words it contains, the order of the words, etc.) with the sentiment. When given new, unlabeled text, it can then predict the sentiment based on these learned associations. The machine learning model used could be a traditional algorithm like Naive Bayes, Support Vector Machines, or a Decision Tree, or a more complex neural network model like a Recurrent Neural Network (RNN), Convolutional Neural Network (CNN), or a transformer model like BERT or GPT.
As the name suggests, hybrid methods combine rule-based and machine-learning-based approaches. They might use a rule-based method to generate features that are fed into a machine-learning model, or use a machine-learning model to predict sentiment, which is then refined using a set of rules. The idea is to try to get the best of both worlds—the linguistic knowledge encapsulated in the rules, and the ability of the machine learning model to learn complex patterns in the data.
How does sentiment analysis work?
The overall process can be divided into several steps:
- Data Collection: The first step involves collecting data for sentiment analysis. This could be social media posts, customer reviews, survey responses, or any other text data where people are expressing their opinions or feelings.
- Text Preprocessing: The collected raw text data often needs to be cleaned and standardized before analysis. This could involve removing irrelevant data (like HTML tags or URLs), converting all text to lowercase, correcting spelling mistakes, removing stop words (commonly used words like “is”, “and”, “the”, etc. that don’t carry much meaning), and other techniques to make the data more uniform. This stage often also involves tokenization (breaking the text into individual words or tokens), and sometimes lemmatization (reducing words to their base or root form).
- Feature Extraction: In this stage, meaningful features are extracted from the preprocessed text data. The simplest approach is the bag of words model, where the text is represented as a set of its words, disregarding grammar and word order but keeping the frequency of each word. More complex approaches could involve word embeddings (where each word is represented as a vector in multi-dimensional space), or even sentence or paragraph embeddings.
- Model Training (Machine Learning Approach): If using a machine learning approach, the next step is to use the features extracted from the text to train a model. The model learns to associate certain features with positive, negative, or neutral sentiments based on the training data. Different algorithms could be used in this stage, including logistic regression, support vector machines, decision trees, or even deep learning models like recurrent neural networks or transformers.
- Sentiment Classification (Rule-Based Approach): If using a rule-based approach, instead of training a model, a set of manually crafted rules are used to determine the sentiment of the text. For example, the text might be classified as positive if it contains more positive words than negative.
- Evaluation: The final step involves evaluating the performance of the sentiment analysis system, usually by comparing its predictions to a set of manually labeled data.
Sentiment Analysis Techniques
Sentiment Analysis Techniques are as follows:
Lexicon-based Sentiment Analysis
This is a simple and straightforward technique in which the sentiment of a text is determined by the words it contains. A sentiment lexicon is a list of lexical features (e.g., words) which are labeled according to their semantic orientation as either positive, negative, or neutral. In this technique, the sentiment of a text is calculated by identifying the sentiment words and the way they’re combined.
Machine Learning-based Sentiment Analysis
This technique uses machine learning algorithms to classify text as positive, negative, or neutral. This is usually done by training a model on a pre-labeled dataset and then using this model to classify new, unseen data. Algorithms used could be traditional ones like Naive Bayes, Support Vector Machines, Decision Trees, or more complex methods like Neural Networks and Deep Learning techniques (e.g., Convolutional Neural Networks, Recurrent Neural Networks, or Transformer-based models like BERT and GPT).
Hybrid Sentiment Analysis
This method combines the lexicon and machine learning-based approaches. For example, it might use a lexicon-based approach to help label data for machine learning, or use machine learning to automate and improve lexicon-based sentiment analysis.
Aspect-Based Sentiment Analysis (ABSA)
In ABSA, the goal is not only to understand the sentiment of the text but also to understand the specific aspects or features that the sentiment is associated with. For example, in a product review, the user might express positive sentiment about the battery life of a phone (aspect: battery life) but negative sentiment about its weight (aspect: weight).
This goes beyond basic sentiment analysis and aims to detect specific emotions expressed in a text, such as happiness, anger, sadness, etc. This could be done using emotion-specific lexicons or more complex machine learning models.
Social Media Sentiment Analysis
Social media platforms like Twitter and Facebook provide a rich source of text for sentiment analysis. Special techniques might be needed to handle the short, informal, and often misspelled or abbreviated text common on these platforms.
Multilingual Sentiment Analysis
This is the application of sentiment analysis techniques to text in multiple languages. This often requires language-specific resources like lexicons and labeled data, as well as techniques for handling translation and cultural differences in how sentiment is expressed.
This is a particularly challenging area of sentiment analysis, as sarcastic comments often say the opposite of what they mean, making them difficult to interpret correctly. Techniques for sarcasm detection often rely on context and common patterns in the way sarcasm is used.
Sentiment Analysis Tool
There are numerous sentiment analysis tools and libraries available that cater to different needs. Some are designed for researchers and data scientists and require programming skills, while others are commercial platforms designed for businesses. Here are a few examples:
- Natural Language Toolkit (NLTK): A popular Python library for natural language processing. It includes functionality for sentiment analysis, along with many other NLP tasks.
- TextBlob: Another Python library that provides a simple API for diving into common NLP tasks such as part-of-speech tagging, noun phrase extraction, and sentiment analysis.
- VADER Sentiment Analysis: VADER (Valence Aware Dictionary and sEntiment Reasoner) is a lexicon and rule-based sentiment analysis tool that’s specifically attuned to sentiments expressed in social media.
- Stanford CoreNLP: A Java-based toolkit providing various NLP tools that support many languages. It includes a sentiment analysis tool.
- Spacy: A Python NLP library that can be extended with separate machine learning models allowing more complex sentiment analysis.
- Google Cloud Natural Language API: A cloud-based tool that uses machine learning to analyze text. It provides sentiment analysis, entity analysis, entity sentiment analysis, and more.
- IBM Watson Tone Analyzer: It provides sentiment analysis and also detects seven tones in written text: anger, fear, joy, sadness, confident, analytical, and tentative.
- Microsoft Azure Text Analytics API: Part of Azure’s Cognitive Services, it provides sentiment analysis, key phrase extraction, and language detection.
- Amazon Comprehend: This is a natural language processing (NLP) service that uses machine learning to find insights and relationships in text. It provides sentiment analysis functionality and supports multiple languages.
- MonkeyLearn: An AI platform that allows you to classify and extract actionable data from raw text. It has pre-trained models for sentiment analysis and also allows you to train custom models.
What are the challenges in sentiment analysis?
Sentiment analysis, while a powerful tool, is not without its challenges. Some of the main challenges include:
- Sarcasm and Irony: Sarcasm and irony involve saying something but meaning the opposite, which can be very difficult for sentiment analysis tools to correctly interpret. For example, a statement like “Oh great, just what I needed” might be labeled as positive by a sentiment analysis tool, while a human would recognize the sarcasm and label it as negative.
- Contextual Ambiguity: The sentiment of a word or phrase can depend heavily on its context. For example, “unpredictable” might be negative when used to describe a car’s handling but positive when used to describe a book’s plot.
- Domain-Specific Language: Different fields or industries might use language in unique ways, including jargon and slang. A word that’s positive in one domain might be negative in another, and a sentiment analysis tool trained on general language data might not be able to accurately analyze text from a specific domain.
- Negations and Double Negatives: Phrases with negations or double negatives can be tricky for sentiment analysis. For example, “not bad” is a positive sentiment, and “not uninteresting” is also generally positive.
- Emotionally Complex Statements: Sentiment analysis often classifies text as positive, negative, or neutral, but human emotions are more complex. A text could contain multiple emotions, or emotions that don’t fit neatly into the positive-negative scale, and a simple sentiment analysis might not capture this complexity.
- Language and Cultural Differences: Sentiment can be expressed differently in different languages and cultures. For example, the same phrase translated into different languages might have different sentiment due to cultural nuances. A sentiment analysis tool trained on English-language data might not work as well on other languages.
- Lack of Labeled Data: Machine learning-based sentiment analysis tools require large amounts of labeled data for training, and it can be time-consuming and expensive to create this data. There might also be a lack of labeled data in specific domains or languages.
Applications of Sentiment Analysis
sentiment analysis is used in a variety of fields and for a wide range of applications, leveraging the fact that much of our communication and expression is now in digital text form. Here are some notable applications:
- Business and Customer Insights: Companies can use sentiment analysis to monitor customer reviews of their products and services on different platforms to understand what their customers like or dislike. This can guide improvements and innovation.
- Social Media Monitoring: Sentiment analysis can help monitor social media platforms to understand public sentiment about a brand, a product, or a service. This can also help in crisis management, as spikes in negative sentiment can be early indicators of a problem.
- Market Research and Analysis: By gauging public sentiment on social media and other online platforms, companies can gain insights into market trends and consumer behaviors, helping them strategically plan their marketing efforts.
- Political Campaigns and Polls: Politicians and political parties can use sentiment analysis to understand public opinion about them or about key issues, allowing them to adjust their campaigns or policies accordingly.
- Financial Market Analysis: Some traders use sentiment analysis to predict market trends. For example, negative sentiments from company reports, financial news, or social media discussions could potentially signal a fall in stock prices.
- Healthcare and Public Health: Sentiment analysis can be used to understand public sentiment about health interventions, disease outbreaks, or health behaviors, which can inform public health efforts.
- Product Analytics: Sentiment analysis can be used to analyze user reviews and feedback about software products. It can help to identify common pain points or highly appreciated features, guiding product development.
- Human Resources and Employee Feedback: Sentiment analysis can be used to analyze employee feedback or comments, helping HR identify common themes, improve employee satisfaction, and reduce churn.
- Entertainment Industry: Sentiment analysis can be used to gauge public opinion about movies, music, games, and other entertainment products. For example, movie producers can use sentiment analysis to predict how well a movie will be received.
- Automated Customer Service: Sentiment analysis can be used in chatbots and other automated systems to detect the sentiment of user inputs and adjust responses accordingly.
Advantages of Sentiment Analysis
Sentiment analysis offers several key benefits, especially in our digitally connected world where vast amounts of textual data are generated every day. Here are some of the primary advantages:
- Customer Insights: Sentiment analysis allows companies to gain a deeper understanding of their customers’ perceptions, opinions, and feelings about their products or services. This information can inform business strategies, guide product improvements, and enhance overall customer experience.
- Brand Monitoring: Companies can use sentiment analysis to keep track of their brand’s reputation in real-time. By analyzing sentiments in social media posts, reviews, and comments, companies can detect shifts in public opinion and respond proactively.
- Competitive Analysis: By applying sentiment analysis on social media conversations or product reviews related to competitors, companies can gain insights into strengths and weaknesses of competitors’ offerings, helping in strategic decision-making.
- Crisis Management: Sentiment analysis can help in identifying negative sentiments in real-time, which can act as an early warning system for crises or issues that need immediate attention.
- Market Research: Sentiment analysis can be used to gauge public opinion on a large scale, which is invaluable for market research. Companies can get insights into consumer reactions towards product launches, marketing campaigns, or events.
- Improved Customer Service: By integrating sentiment analysis in customer service, companies can prioritize responses based on sentiment scores. Customers with negative sentiments can be prioritized to improve their experience and mitigate potential churn.
- Efficient and Scalable: Manual analysis of textual data can be incredibly time-consuming, particularly when dealing with large volumes of data. Sentiment analysis automates this process, making it more efficient and scalable.
- Enhanced Employee Feedback Analysis: Organizations can use sentiment analysis to understand employee feedback, identify areas of improvement, and foster a better workplace environment.
Disadvantages of Sentiment Analysis
Despite its many advantages, sentiment analysis also has its limitations. Here are some of the key disadvantages or challenges:
- Difficulty with Sarcasm and Irony: Automated sentiment analysis systems can struggle with understanding sarcasm and irony, which often involve saying one thing but meaning the opposite. This can lead to misinterpretation of sentiments.
- Understanding Context: The sentiment value of certain phrases may change based on the context in which they’re used. Sentiment analysis algorithms may find it challenging to correctly interpret such context-dependent phrases.
- Handling Negations: Sentiment analysis systems might struggle with phrases that include negations. For example, the phrase “not great” is negative, but a simplistic sentiment analysis algorithm might interpret it as positive because it contains the word “great”.
- Lack of Nuance: Most sentiment analysis tools categorize text into positive, negative, or neutral sentiments. Human emotions, however, are far more complex and nuanced. As a result, such tools might oversimplify the sentiment.
- Cultural and Linguistic Differences: Sentiment analysis tools might struggle with slang, idioms, and language-specific expressions. In addition, they might not account for cultural differences in expressing sentiments.
- Need for Large Amounts of Labeled Data: Machine learning-based sentiment analysis tools require large amounts of labeled data for training. Creating this data can be time-consuming and expensive, and there might be a lack of labeled data in specific domains or languages.
- Accuracy: The accuracy of sentiment analysis can vary depending on the complexity of the text and the quality of the tool used. Misinterpretations can lead to misleading conclusions.
- Spam and Bots: In areas like social media analysis, it’s often difficult to distinguish between genuine user content and content generated by spam or bots. This can influence the sentiment analysis results.