HCI Theories, Part 1: Classical Theories Explained

Published on Sunday, April 17, 2016
Last updated Wednesday, October 25, 2023
4 min read

Human-Computer Interaction (HCI) isn't just about coding and design; it's also deeply rooted in understanding human behavior. In this first part of our multi-part series, we'll dive into what HCI theory is and explore some of the classical theories that have shaped the field.

Why Does Theory Matter in HCI?

Think of HCI theories as the backstage crew in a theater production. You may not see them, but they guide everything that happens on stage. These theories draw from various fields like psychology, anthropology, and even biology, blending them to understand how humans interact with technology.

The Building Blocks: Classical Theories in HCI

Cognitive Psychology

Ever wondered why some apps feel intuitive while others don't? Cognitive psychology helps us understand what people can (and can't) do easily when interacting with tech. While lab studies offer insights, real-world behavior is often more complex. Knowing the basics of cognitive psychology can inform better design decisions.

Example: Ever notice how some websites use color contrasts to highlight key buttons? That's cognitive psychology at work, tapping into how our brains process visual information.

Cognitive Modeling

Imagine you're designing a new email platform. How do users decide to categorize their emails? Cognitive Modeling helps you make educated guesses about user behavior, which you can then validate through user research.

Example: When designing an email platform, cognitive modeling could predict that users might want to categorize emails based on sender importance rather than chronologically. Design choices could then cater to these assumptions for better usability.

Interface Gulfs: Bridging the Gap

In the world of HCI, we talk about two main "gulfs":

  1. Gulf of Execution: What steps does a user need to take to make something happen?
  2. Gulf of Evaluation: Did the action produce the desired result?

In simple terms, it's a never-ending cycle we all go through: we take an action (execute), see what happens (evaluate), and then plan our next move based on that feedback. This cycle continues until we achieve what we set out to do.

Diagram of the gulfs of evaluation and execution as they mediate between users and systems in the world.
The diagram illustrates a common user experience journey, marked by two key hurdles: the Gulf of Execution and the Gulf of Evaluation.

Designing with these gulfs in mind helps minimize the mental effort needed to use a product.

Example: Think about a simple act like deleting an email. The "gulf of execution" is how easily you can find the delete button. The "gulf of evaluation" is how clearly the interface confirms the email has been deleted.

GOMS and the Model Human Processor

GOMS (Goals, Operators, Methods, and Selection) is like a playbook for HCI pros. It helps predict user behavior by breaking down actions into smaller components. It's based on the idea that our brain has different processors for perception, thinking, and doing.

Diagram showing the concepts of a GOMS model and their relationships.
GOMS is a kind of specialized human information processor model for human computer interaction observation.

Example: Imagine you're designing a calendar app. GOMS can help predict how long it would take a user to add a new event, which can then inform your design choices to streamline that process.

Mental Models: Bridging the Designer-User Gap

Great design aligns the mental model of the designer with that of the user. When these mental models clash, that's where confusion arises.

Example: If a designer assumes that users know to swipe left to access a menu, but users are trying to tap an icon instead, there's a mental model mismatch.


While HCI theories can sometimes feel abstract, especially if you're not from a scientific background, they offer invaluable frameworks for understanding user behavior. They aren't one-size-fits-all solutions, but more like lenses to view and solve design challenges.

Further Reading