What is Underfitting?

  • Editor
  • January 26, 2024

What is underfitting? It is a common challenge in the field of artificial intelligence (AI) and machine learning, where a model is too simple to capture the underlying patterns and complexities of the training data.

This occurs when the model fails to learn enough from the data, leading to poor performance not only on the training data but also when generalized to new data.

Looking to learn more? Keep reading through this article written by the AI Enthusiasts at All About AI.

What is Underfitting? AI’s Little Oops Moment!

Imagine you’re trying to draw a picture of your backyard. But, instead of looking at all the details like the flowers, trees, and the little birdhouse, you just draw a quick sketch with only a few lines. This is a bit like underfitting in the world of computers and robots.

Underfitting happens in artificial intelligence (AI) and machine learning, which is like when computers learn to do things on their own.

If we give a computer a job, like figuring out what pictures have cats in them, we need to teach it how to do that. We show it lots of pictures, some with cats and some without, and it tries to learn the pattern of what makes a cat a cat.

Key Characteristics of Underfitting:

Underfitting in machine learning and AI models occurs when a model is too simplistic to capture the complexities of the data. It is characterized by:

  • High Bias: Underfit models have high bias, meaning they make strong assumptions about the data and often oversimplify the problem, leading to a failure in capturing underlying patterns.
  • Low Variance: These models exhibit low variance, indicating they do not significantly change with different training datasets.
  • Poor Generalization: Underfit models perform poorly not only on new data but also on the training data itself, indicating a failure to learn the essential features of the data.
  • Simplistic Model Design: Often, underfitting is a result of a model that is too simple for the complexity of the task at hand, lacking the necessary structure to understand deeper insights from the data.

Underfitting vs. Overfitting:

While underfitting involves a model that is too simple, overfitting is the opposite scenario where the model is too complex.


Overfit models capture noise and random fluctuations in the training data as if they were significant features, leading to poor model generalization. In contrast, underfitted models overlook the significant patterns in the data.

  • Model Complexity: Overfitting involves overly complex models that capture noise, while underfitting is due to overly simplistic models.
  • Data Performance: Overfit models perform well on training data but poorly on unseen data. Underfit models underperform on both.
  • Bias and Variance: Overfitting is characterized by low bias and high variance, whereas underfitting involves high bias and low variance.
  • Learning from Data: Overfit models learn too much from the training data, including noise, while underfit models fail to learn enough.
  • Adaptability: Overfit models are too tailored to the training data and fail to adapt to new data, whereas underfit models are not adequately tailored even to the training data.

Causes of Underfitting:

Underfitting can arise from several factors including insufficient model complexity, inadequate feature selection, lack of regularization, and insufficient training data.

It is often a result of an overly simplistic approach to modeling the data, neglecting the intricate patterns present.

  • Insufficient Model Complexity: Overly simple models lack the capacity to understand complex data structures and relationships.
  • Poor Feature Selection: Neglecting to include enough relevant features limits the model’s predictive capabilities.
  • Inadequate Data: A limited or non-diverse dataset restricts the model’s ability to learn effectively.
  • Excessive Regularization: Over-regularization can suppress the model’s learning ability, leading to oversimplification.
  • Incorrect Algorithm Choice: Choosing an inappropriate algorithm can fail to address the data’s complexity adequately.

Consequences of Underfitting in Models:

The primary consequence of underfitting is reduced model accuracy and poor performance. This can be particularly detrimental in data science applications where predictive accuracy is crucial.

Underfitted models tend to have high training errors and are ineffective for practical applications.

  • Models that underfit yield inaccurate predictions, failing to utilize the depth and richness of the data effectively.
  • Performance issues arise on both training and testing data, indicating a fundamental flaw in the model’s learning process.
  • Such models are unreliable for practical applications, limiting their effectiveness in real-world scenarios.
  • Poorly fitted models can lead to incorrect decisions, especially in critical areas like healthcare or financial forecasting.
  • Underfitting reduces the return on investment in artificial intelligence projects, as these models fail to meet the expected performance levels.
  • Adapting these models to new or evolving datasets is challenging, reducing their scalability and long-term utility.

Solutions to Prevent Underfitting:

Preventing underfitting involves enhancing model complexity, improving feature selection, and ensuring adequate training data.

Regularization techniques can also be employed to strike a balance between simplicity and complexity in the model.

Additionally, iterative testing and model tuning are key to preventing underfitting.

Increasing Model Complexity:

Incorporating more complexity allows the model to better understand and interpret intricate data patterns.

Improving Feature Engineering:

Effective feature selection and transformation are crucial for enhancing the model’s predictive power.

Expanding Training Data:

Utilizing a more extensive and diverse dataset equips the model with a broader range of information to learn from.

Practical Applications Of Underfitting:

Understanding underfitting is essential in applications where model accuracy and generalization are critical.


In fields like healthcare, finance, and autonomous systems, recognizing and addressing underfitting can lead to more reliable and effective AI solutions.

Predictive Analytics:

Correcting underfitting is vital for accurate forecasting in various sectors like business, finance, and meteorology.

Medical Diagnosis:

In healthcare, ensuring models are adequately fitted is essential for developing reliable diagnostic tools.

Customer Segmentation:

Addressing underfitting in marketing models aids in accurate customer segmentation and targeted marketing strategies.

Risk Assessment:

In finance, well-fitted models are critical for sound risk assessment and decision-making processes.

Image Recognition:

In computer vision, resolving underfitting ensures models accurately interpret and recognize images, vital for applications like facial recognition.

Case Studies – Underfitting:

Case studies in various sectors, from healthcare to finance, illustrate the impact of underfitting on model performance and the strategies employed to overcome it. These real-world examples provide valuable insights into managing underfitting in practical scenarios.

Breast Cancer Prediction (2011):

A model trained for predicting breast cancer risk performed well on training data but underperformed on new data, indicating a balance issue between overfitting and underfitting, which is crucial in medical predictive models​​.

Autism Risk in Children (2013):

A model designed to assess autism risk in children showed poor performance on testing data, a clear sign of underfitting. This highlights the complexities and challenges of developing accurate predictive models in healthcare​​.

Want to Read More? Explore These AI Glossaries!

Dive into the realm of artificial intelligence with our meticulously selected glossaries. Suitable for novices and experts alike, you’re bound to uncover fresh insights!

  • What Is the Diffusion Model?: The diffusion model refers to a machine learning framework that progressively transforms data from a simple, random distribution into a more complex one that represents the desired outcome.
  • What Is Dimensionality Reduction?: Dimensionality reduction is a process in artificial intelligence (AI) and data analysis where the number of random variables under consideration is reduced.
  • What Is Disambiguation?: It refers to the process by which AI systems accurately interpret and clarify ambiguous data or language.
  • What Is a Discrete System?: A discrete system refers to a computational model characterized by distinct and separate states or values.
  • What Is Distributed Artificial Intelligence?: Distributed Artificial Intelligence (DAI) is an area of Artificial Intelligence that focuses on the development of systems where multiple autonomous entities, or agents, interact or cooperate with each other to solve problems or complete tasks.


An underfit model could be a linear regression model trying to predict housing prices while ignoring critical features like location and age of the property.

Underfitting is problematic because it leads to poor model performance and inaccurate predictions, which can be costly and misleading in critical applications.

No, underfitting is characterized by high bias, where the model oversimplifies the problem and ignores the complexity in the data.

More data can help, but it is also crucial to enhance the model’s complexity and feature selection to effectively address underfitting.


Understanding and addressing underfitting is crucial in the development of effective AI models. By recognizing the signs of underfitting and implementing strategies to enhance model complexity and accuracy, AI practitioners can ensure their models are well-suited for the complexities of real-world applications.

This article comprehensively answered the question, “what is underfitting,” explaining this concept in the context of AI. Looking to learn more about the world of AI? Read through the rest of the articles in our AI Language Guide.

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Dave Andre


Digital marketing enthusiast by day, nature wanderer by dusk. Dave Andre blends two decades of AI and SaaS expertise into impactful strategies for SMEs. His weekends? Lost in books on tech trends and rejuvenating on scenic trails.

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