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What are “Mental Models”?

Editor’s note: This is part one of a two part series on Systems Thinking and mental models

In writing and teaching people about Systems Thinking, we often refer to “mental models”.  For some people, this comes as a bit of a surprise, because the context usually involves building models with the iThink or STELLA software.  They don’t expect us to start talking metaphysically about thinking.  “Is this about philosophy or modeling software?” they may wonder.  The software is actually a tool to help construct, simulate and communicate mental models.

Let’s define the term model: A model is an abstraction or simplification of a system.  Models can assume many different forms – from a model volcano in a high school science fair to a sophisticated astrophysical model simulated using a supercomputer.  Models are simplified representations of a part of reality that we want to learn more about.  George Box stated: “Essentially, all models are wrong, but some are useful”.  They are wrong because they are simplifications and they can be useful because we can learn from them.

So, what is a “mental model”?  A mental model is a model that is constructed and simulated within a conscious mind.  To be “conscious” is to be aware of the world around you and yourself in relation to the world.  Let’s take a moment to think about how this process works operationally.

Thinking about trees

Imagine that you are standing outside, looking at a tree.  What happens?  The lenses in your eyes focus light photons onto the retinas.  The photosensitive cells in your retinas respond by sending neural impulses to your brain.  Your brain processes these signals and forms an image of the tree inside your mind.

So at this point, we’ve only addressed the mechanisms by which you perceive the tree.  We have not addressed understanding what a tree is or considered changes over time.   We are dealing with visual information only.  There is nothing within this information that tells you what a tree actually is.

What makes the image of a tree in your minds click as an actual tree that exists right there in front of you?  This is where mental models kick in and you start to think about the tree.  The tree is actually a concept of something that exists in physical reality.  The “tree concept” is a model.  Understanding the concept of a tree requires more information than is available through sensory experience alone.  It’s built on past experiences and knowledge.

A tree is a plant.  It is a living thing that grows and changes appearance over time, often with the seasons.  Trees have root systems.  Trees use leaves for photosynthesis.  Wood comes from trees.  I can state these facts confidently because I have memories and knowledge of trees contained within my mental models.  Mental models contain knowledge and help us create new knowledge.


Take a look at these images for a few moments and then think about what is happening inside your mind as you look at them.

Boy catching a ball Blocks Toddler reaching for a hot stove

My guess is that with each image you thought about what happens next.  If so, you were actually simulating a mental model forward in time.  The images don’t show you what happened next, but you can probably make a pretty good guess.  This guess is the result of simulating a mental model of what is depicted.  And, you can simulate different outcomes.  In the image on the right, I like to simulate a parent rushing into the scene and scooping up the child before he gets burned.

When we think about the boy catching the ball, the blocks knocking one another over, worrying about the toddler getting burned, we are applying knowledge that we hold in our minds to help simulate a mental model of what is depicted in the image.  This is all going on subconsciously, so we’re really not aware of it as it is happening.

Thinking About Systems

The human mind is very good at simulating mental models of our immediate physical reality.  Things get harder when we start thinking about abstract systems.

A market is a good example of an abstract system.  In a market system, price acts as a signal of aggregate demand for a commodity.  You can’t “see” a market like you can “see” a tree in front of you.  A market does not exists in a particular physical location.  A market is an abstract concept that exists in the collective minds of all who participate in it.  Even though a market does not exist physically, markets have an enormous impact on our lives nonetheless.

When the global economic crisis hit in late 2008, retailers began to struggle financially because consumer purchases declined rapidly.  People were worried about the economy and started saving money instead of spending it.  This started happening just before the holiday shopping season – a make-or-break period for many retailers.  So, in an effort to boost demand, retailers began dropping prices.

consumer perspective

This led to price deflation because consumers saw prices dropping rapidly and began delaying purchases as a result.  The outcome of simulating their mental model of the market informed their decision making: “I should wait to buy this because the price keeps dropping”.

This mental model paints a pretty picture for consumers over the short-term:  low prices in a down economy.  As the deflationary dynamics play out over the long term, the picture becomes bleak.  As prices spin downward, profits decline and businesses are forced to layoff workers or close up shop entirely.  As unemployment increases, consumers perception of the stability of the economy decreases and they spend even less.


Economists and policy makers use sophisticated computer models to help them understand markets.  On the other hand, consumers use simple mental models when making purchasing decisions.  The more sophisticated models inform policy makers of the long term consequences of consumers cutting spending, so they react by trying to jump-start spending with stimulus programs.  In the US we’ve seen a few of these programs during 2009: the “Cash for Clunkers” rebate program, the First-Time Home Buyer Tax Credit, and the Social Security payroll tax cut.

Often, it is hard for us to define the optimal boundaries for a mental model.  We tend to have a narrow focus and act on short-term dynamics within our mental models.  For example, in the model above, our understanding changes when we expand the boundaries to include profits and layoffs.

However, we are not generally very good at mentally simulating complex systems with interdependencies, lots of variables, and delays.  This is where software steps in.  Using Systems Thinking software, we can transform our mental models into operational models that we can simulate more reliably using a computer.  This not only helps us create new knowledge and understanding, but helps us construct better mental models in the future.

We’ll explore the role of software in constructing, simulating and communicating mental models in part two of this series.


For more on using modeling and simulation to understand the economic crisis, see the “Understanding the Economic Crisis” video presentation.

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  • A fantastic blog that simplifies the concept of how do we use mental models to take decisions

  • Jeremy, do layoffs actually add to the stability of economy? I thought it would be the opposite. maybe I missed something in the description.

    • Great catch — it should be – (negative) or opposite polarity. I have updated the image. Thanks!

  • Timoka

    Excellent presentation of mental modeling. Now I understand more of the concept. However, I wonder: What is the relation of mental modeling compared with the dualistic thinking of Descartes. Descartes divided the world into two parts or domains, i.e. the world of materia with measurable dimensions and the world of human mind with immeasurable dimensions. Most of Western thinking and progress is based on the human success in the world of materia. Nowadays we might be facing a new situation. Materialism seem to endanger the climate and the future of global nature as a whole. I wonder if is possible to model this danger. How do you do it? What is the role of mental modelling and roles of other types of modeling. Do we still keep on going on the road of materialism or Box's ( all modes are wrong , but some useful). If not, what is the New Road to go? How do we get into that sustainable road? Perhaps we need a new Kolumbus, who takes us to the New World? Any candidates of Kolumbus???

  • Simon Ellberger

    Jeremy: The definition you give of a “mental model” is very different from that given by Peter Senge in The Fifth Discipline, the seminal book that popularized systems thinking and mental models. In it, Senge states: “Mental models are deeply ingrained assumptions, generalizations, or even pictures or images that influence how we understand the world and how we take action. Very often, we are not consciously aware of our mental models or the effects they have on our behavior.” Could you please comment on this?

    • Simon – I am on the same page with Peter Senge. In the Fifth Discipline, he describes a continuum of mental models—from Plato’s parable of the cave, the “Emperor’s New Clothes”, examples of ingrained assumptions of the automakers at General Motors, to physicist’s mental models of twentieth-century physics (which required them to change their mental models completely to understand).

      In part one of this post, I try to shed some light on one extreme of that continuum–the subconscious mental models of immediate physical reality. This is fundamental to our experience of physical reality. I’m arguing that mental models are actually required for a mind to be “conscious”. I hope this will lend some validity to the mental models concept for the skeptics.

      In part two, I write about the other end of the continuum: how we use mental models to create new knowledge and understanding. (This is related to Peter’s example of physicists developing the theory of relativity and quantum mechanics.)

      (Part two will be posted soon)

      • Ali

        I wonder if mental models and paradigm are the same?

  • Jim Thompson

    One's mental model is a construct of one's thought used to make sense of one's experiences.

  • System models though might not be able to predict the magnitude of any action it however, can identify the trend and behavior. System models can shed important insights on the properties hidden in symmetries. These benefits can only be materialized when information acquiring process is economized. Filtering irrelevant information and modeling using only the tight feedback loops makes the model robust. In the above example of consumer-products market, deflation was not the only factor resulting in price drops, nor was the layoffs sole contributor to economic decline there were range of other factors directly and indirectly affecting it which were omitted because they were less tightly coupled with the consumer market. Likewise, deflation not only caused impacts along consumer-goods market. It created ripple effect in different levels of economic system. Both horizontal and vertical reach of inflation had to deal with the shock. The above example does not capture all these interactions. System models like this are built using the concept of near-decomposability where sub-systems are created with localized rules for interactions.

    • Correct. The causal loop diagram is a representation of the simplified mental model. It is simplified, but very powerful because it includes feedback loops.

      In part two, we'll be expanding that mental model into an operational model that we can simulate on the computer.

  • lisagalley

    Thanks, this is a pretty easy to read presentation of concepts that can be quite hard to grasp.

  • rossibella

    Hi Were are you? very good page. I am new to these tools and how little I learned in 2 months, I perfectly situated right now working on the report of my internship requirement for my graduation here in Venezuela. My work is about the global system of exploitation of oil or the behavior of oil production, internet buscandio Got a Systemodinamics veersion Stella Hubbert Model which works mainly with the feedback loop but I am doing something similar but not the same but the graphics do not give me the pot so I only lasts a year and a few months and should not be so that is why I am asking for help. I would appreciate that could help me or guide me as to my model because it is important to me because now my time is almost over and as I have said is an important requirement for my graduation. Beforehand thank you very much and I expect a prompt reply, This is my mail rosvir73@hotmail.com in case you have something that I can be of help or support. Thank you.

  • rossibella

    Hello as they are, will I can say or guide on how to use the Buitin? with that syntax or used? is something I am entangled in my project and I need your help to know if I can use them or not, since it is not about to get material, some things. Thanks, I hope to answer ..

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  • not bad at all

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