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Mental models represent a very important way to view the way we think. More importantly, models in general represent a very useful way to represent known knowledge. The significance of models might not be obvious, but I’m going to try and paint a picture that will help you understand them as I do. First though, I’m going to focus on mental models. And before we get into them, I’m going to tell you a story describing the context in which I discovered mental models.

Despite the fairly recent surge of interest in interface design fueled by Web 2.0 and companies like Apple, the field has quite a large body of work behind it. In fact, it’s part of a rather amazing ecosystem of inter-disciplinary fields. Rooted in the context of cognitive psychology, interface design falls under the umbrella field of human-computer interaction (HCI). HCI didn’t get much attention until the mid 80’s, but since then has exploded into an entire sea of fields and methods, really to the point of insanity.

Some of these fields got more specific, and some of them got more general. In fact, today it’s common practice to talk about interaction design, which is essentially a more general form of interface design that doesn’t necessarily have to be about technology. In most cases though, interaction design is usually used in the context of HCI, just as with information architecture, usability engineering, affordance analysis, cognitive walkthrough method, and the bajillion other offshoots.

With all the activity that’s happened, not much more theoretical work has come out of HCI in the recent years with the exception of social software. Most of the information you read about interaction design today can be found in textbooks from the early 90’s. Even The Design of Everyday Things, the book that inspires most people to study interaction design, was originally published in 1988. Like so many fields, the work has been done, but the application has been lacking.

That shouldn’t be surprising. What is surprising is the amount of work that has been done in this area. If you look at all the ideas that were put into and came out of HCI and the contexts they’re being used in, it really shows you just how inter-disciplinary the field is.

Experience design, a superset of interaction design, is just about as all-encompassing as systems theory. Everything we do in life is an experience, so just about every conscious decision to do something could be considered an act of experience design.

Now, there’s a lot I’d like to talk about in this area, but right now I want to focus on one important idea that I’ve gotten from HCI. It’s had a tremendous impact on the way I think and the way I think about thinking.

This is a theory that interaction design popularized from cognitive psychology called mental models. Today, the idea of mental models in interaction design is usually just glossed over as a tool that can be used to talk about the design of interactive experiences.

It turns out that the theory of mental models unlocks an interesting way to relate everything together using systems theory, experience design, and this mysterious thing we think we understand called computation. I’m going to try and explain this to the best of my ability over a number of blog posts.

So for now, what are mental models?

In 1899, physicist Ludwig Boltzmann said, “All our ideas and concepts are only internal pictures.” The problem with this idea is that pictures are static. We live an a very dynamic and interactive world. In order to fully cope with this, the mind constructs models of reality, not unlike scale models of bridges or buildings, that it uses to reason, anticipate events and underlie explanation.

In other words, as we interact with reality, we build models of it in our heads, which we then interact with and use later to make short-term predictions and solve problems.

The idea came from Kenneth Craik, one of the earliest practitioners of cognitive science. Unfortunately, he died of a bicycle accident in 1945, two years after publishing the book that introduced mental models called The Nature of Explanation. In his words:

If the organism carries a “small-scale model” of external reality and of its own possible actions within its head, it is able to try out various alternatives, conclude which is the best of them, react to future situations before they arise, utilise the knowledge of past events in dealing with the present and future, and in every way to react in a much fuller, safer, and more competent manner to emergencies which face it.

A common way to explain mental models is with a little exercise. Off the top of your head, try to answer how many windows you have in your home. Don’t know? Over 9000? How would you try to answer this more thoughtfully? Most likely, you’d imagine your home and in your mind you’d walk through the various rooms and count all the windows.

What you did is you built a mental model for the purpose of this problem, based on your previously stored mental model of your home. Through interacting with it, you solved the problem to some degree of accuracy based on how well you remember your home. For most that shouldn’t be hard. You’ve stored and reinforced that model with every step in the actual thing.

Mental models are also used the same way people use Excel spreadsheets to try out “what if” situations. I’m standing in line at the airport for security and somebody says there’s another line on the other side. What happens if I get out of this line to try the line on the other side? Will it be shorter? Will I end up in a longer line because I lost my place in the original line? Is it worth the chance? Well, I can quickly model these situations in my head to make a decision. Or not. I’m rather indecisive.

In practice, most of the time the visualization isn’t done because, well, if it’s not necessary, it wouldn’t be efficient. But that doesn’t mean you aren’t working with a model that, however abstract, represents some aspect of the real world.

In fact, mental models aren’t just used to model physical aspects of reality, but conceptual as well. This is because even though the main definition of the word “model” is a 3-D representation of something, the key idea common across all uses of model is representation.

A model is a representation of something, which makes it a fairly versatile concept. However, the metaphors associated with “model” make it a much more powerful communication tool than “representation.”

So a mental model is your internal representation of some knowledge. It could be of physical space, a scientific theory, a rule of mathematics, or your idea of how something works, such as the behavior of people or your toaster.

Mental models are used in the context of interaction design for the purpose of understanding learnability and ease of use. Donald Norman’s book The Design of Everyday Things describes how a system is designed and implemented on the basis of the designer’s mental model. The user of the system then develops their own mental model of the system, which is used to reason about the system, anticipate system behavior, and explain why the system reacts the way it does.

Ideally, the designer can construct the interface in such a way that would produce a model in the mind of the user that would allow them to get the most out of the system. This usually means conveying the mental model of the designer to the user, but that’s not always the case.

In fact, it’s been a common trend to build a separate “conceptual model” into the interface that differs from the designer’s mental model in order to make the system appear more graspable and lucid to the user. However, the idea of focusing on what the user can understand more than what the user will tend to model resulted in many wasted efforts in the early 80’s.

Game designer Will Wright uses the concept of mental models very heavily in his work. He argues that games run on two processors, that of the computer and that of the mind. The mind complements what the computer renders with its own rendering—its own model—that’s used to fill in the blanks of the abstractions in the game and create immersion.

Wright even uses mental models to explain the purchasing behavior of video game consumers, which to some extent can be applied to any retail product. He says that when the consumer is browsing the store and catches just the title of the game, the consumer starts to build a mental model of what they think the game is about.

As they look closer at the box cover and then turn it over to study the back of the box, they build a more and more elaborate mental model of what the game is like even before playing it. If their mental model of the game seems like something they’d want to play, they’re going to want to buy it.

In a reality dominated by the mind, the understanding of human psychology is a powerful tool. If we think in models, then understanding models will provide great insight into the way we think.

I believe dreaming is an exercise of building mental models without constraint. Imagination is an act of modeling. Humans are unique in that they constantly model the world around them. It’s our way of dealing with reality and feeding our intelligence.

Next up, I’m going to talk about models in general and their wider application.

This entry was posted on Tuesday, January 30th, 2007 at 7:23 pm and is filed under Design, Abstract, Systems Theory, Models. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.