What is Model Behavior?
Model behavior is the way in which a trained ML model makes predictions and decisions when it is exposed to new data, usually when it is deployed in production and used for real-world use cases. Model behavior is influenced by the data that the model was trained on, the model’s parameters and the environment in which the model is deployed. By understanding how a model behaves, we can ensure that it is accurate, robust, interpretable and fair.
Model behavior is measured and monitored with metrics like accuracy, precision and recall to identify drift and measure performance. In addition, model behavior is monitored to understand why the predictions and decisions were made the way they were, for interpretability, explainability and transparency purposes. Finally, data professionals monitor behavior to ensure that model behavior is fair and unbiased, while implementing ethical AI and responsible AI practices.
Why is Model Behavior Important?
It is important to understand and monitor ML model behavior in production in real-world applications. This ensures:
- Model Accuracy and Reliability – Poor model behavior and inaccurate predictions can lead to incorrect results. This impacts the user experience and business results. When Ml models are used for mission-critical services or life-saving procedures, like medical diagnoses, the consequences of inaccurate models can be extremely severe.
- Generalization – The ML model needs to perform reliably and accurately on unseen data. If a model is overfitting or underfitting, its applicability in a real-world setting is compromised.
- Resource Efficiency – Some models may be accurate but computationally expensive. Understanding a model’s behavior can help optimize its performance, while also optimizing computational resources.
- Interpretability, Transparency and Trust – It’s important to understand why the model makes the predictions it does. A model that can be explained gains more trust from end-users and decision-makers. In some cases, compliance regulations do not allow for deploying an uninterpretable model.
- Ethical and Legal Considerations – Models that behave unpredictably or show bias or toxic behavior can lead to ethical and legal repercussions. For example, a biased hiring algorithm or profiling model could lead to discrimination and lawsuits.
- Robustness – Real-world data can be noisy and full of anomalies. A well-behaving model should be robust enough to handle this data without it impacting performance.
- Real-time Adaptability – In online and streaming environments, the model needs to adapt to changing conditions. Monitoring the models’s behavior will show when the model needs to be retrained.
- Debugging – Understanding model behavior helps debug it. This ensures that the model remains effective and useful over time.
How to Explain ML Model Behavior
As mentioned, explaining ML model behavior is important for ensuring model accuracy, reliability, robustness, fairness and generalization. Here are some approaches to achieve this:
Interpretability Techniques
- Feature Importance – Algorithms like Random Forests and Gradient Boosting Machines provide feature importance scores, which can help in understanding which features are driving the predictions.
- Partial Dependence Plots (PDPs) – Plots that show the relationship between a feature and the target variable, keeping other features constant. This helps understand how individual features affect predictions.
- Local Interpretable Model-agnostic Explanations (LIME) – LIME approximates a complex model with a simpler one for individual predictions, making it easier to interpret why a specific prediction was made.
Surrogate Models
- Decision Trees – A simpler model like a decision tree can be trained to approximate the behavior of a more complex model. The decision tree can then be analyzed for insights.
- Linear Models – For some problems, linear models can serve as good approximations and are easier to interpret.
Visualization Tools
- Heatmaps – In image classification tasks, heatmaps can show which parts of the image were most relevant for making a particular classification.
- t-SNE or PCA – Dimensionality reduction techniques that can be used to visualize high-dimensional data and model decisions in a 2D or 3D space.
Sensitivity Analysis
- What-If Analysis – Changing input features and observing the change in output can provide insights into model behavior.
- Monte Carlo Simulations – Running the model on a large number of generated samples can help understand its behavior under different conditions.
Text-based Explanations
- Natural Language Generation (NLG) – Some models can generate textual explanations for their decisions, which can be particularly useful in healthcare or legal settings.
Counterfactual Explanations
- Explaining by Example – Providing examples of similar instances with different outcomes can help in understanding why a particular decision was made.
Auditing and Monitoring
- Real-time Monitoring – Keeping track of model predictions and performance metrics in real-time can help in understanding its behavior and making necessary adjustments.
- Fairness Audits – Tools and metrics designed to measure and explain bias in models can be used to ensure ethical behavior.
How to Monitor Model Behavior
There are a number of strategies used to monitor and watch ML model behavior. The prominent ones are:
Automated Monitoring Systems
- Automated Anomaly Detection – Implementing real-time monitoring systems that automatically flag anomalies in model behavior, like sudden drops in accuracy or false positive spikes.
- Threshold Alerts – Setting predefined thresholds for key performance metrics. If the model crosses these thresholds, automated alerts can be sent for immediate review.
Continuous Validation
- Rolling Validation – Continuously validating the model on new data. This ensures that the model is still relevant and performs well on current data.
- A/B Testing – Deploying multiple versions of the model and comparing their performance in real-time. This allows for continuous improvement and fine-tuning.
Explainability as a Service
- Integrated Explainability – Building explainability into the model itself, so that each prediction comes with an automatically generated explanation.
- User Feedback Loop – Allowing end-users to question or challenge model predictions, which provides valuable feedback that can be used to improve the model.
Governance and Accountability
- Model Audits – Regularly auditing the model for fairness, bias and ethical considerations and making the audit results publicly available for transparency.
- Version Control – Maintaining a version history of the model, including changes, who made them and why. This creates a traceable record of model behavior over time.
Ethical and Legal Compliance
- Compliance Checks – Ensuring that the model meets all legal and ethical standards, including data privacy regulations like GDPR.
- Third-party Audits – Third-party audits for an unbiased review of the model’s behavior, especially in sensitive applications like healthcare or finance.
Human-in-the-loop (HITL)
- Expert Review – Involving domain experts in the review process. Their insights can be invaluable in understanding complex or nuanced behavior.
- Escalation Protocols – In critical applications, having protocols to escalate decisions to human experts when the model’s behavior is uncertain or falls outside predefined bounds.
