I've read about "Mental Model Law", which states that it is significantly easier for users to understand and learn something new if they can model it off of something they already understand.

Can't found it on the internet. Does this principle have another name? I need to make a reference to exact law, principle or research.

  • Perhaps providing the sentence or line that needs citing will help clarify which 'law' you are trying to reference.
    – Ken
    Nov 3 '14 at 15:56

Yes, there is research on mental models, but not too recent. Also, it comes from the academic part of the usability community, not the new UX bloggers, so it doesn't contain "laws" or similar.

The best explanation of mental models I know is in Fix93. Staggers93 also has a good article on them.

Note that the concept is not so "modern" or well known today, so some younger authors use the word as a homonym for completely unrelated concepts. For example, Rosenfeld media has published a book called "Mental models" which has nothing to do with the original mental models, but describes a kind of diagram showing a user's routine tasks. It is not a bad read in itself, but very disappointing if you are interested in the original, and annoying to have to deal with a homonym.

I find the original mental models very important knowledge in UX. Design for users who do have a mental model in their head is totally different from design for users who don't. In the worst (but very common case) you have to support a mix of both kinds, and this needs lots of fine tuning.

Fix, Vikki, Susan Wiedenbeck, and Jean Scholtz. "Mental representations of programs by novices and experts." Proceedings of the INTERACT'93 and CHI'93 conference on Human factors in computing systems. ACM, 1993.

Staggers, Nancy, and Anthony F. Norcio. "Mental models: concepts for human-computer interaction research." International Journal of Man-machine studies 38.4 (1993): 587-605.

  • Nice to see some academic references ;-)
    – PhillipW
    Nov 3 '14 at 16:43

I would use Nielsen Norman Group as a reference - arguably some of the most trustworthy authors regarding UX and interaction design.

... you have to suffer one bit of theory — namely the definition of mental models. A mental model is what the user believes about the system at hand.

... mental models are in flux exactly because they're embedded in a brain rather than fixed in an external medium. Additional experience with the system can obviously change the model, but users might also update their mental models based on stimuli from elsewhere, such as talking to other users or even applying lessons from other systems.



There's no mental model "law", but it's one of the more important concepts in UX design. It isn't a modern concept either although Don Norman and Steve Krug have talked about it quite a bit in their books.

There are complimentary topics such as conceptual models and system image too which might be worth looking at.

Here are a few good reads on the topic:

http://www.nngroup.com/articles/mental-models/ http://www.jnd.org/dn.mss/design_as_communication.html

I'd also recommend reading Phillip Johnson-Laird's How We Reason. It talks about how our reasoning is based on mental models. In any case, insights into human psychology help you design better experiences.

  • I think Don's been talking about it in his books since 1983...
    – PhillipW
    Nov 3 '14 at 16:38
  • Yep. He has been talking about for quite some time. :-)
    – swastik
    Nov 3 '14 at 18:24
  • And I see Don submitted a chapter on a book on the topic back in 1983...en.wikipedia.org/wiki/Mental_Models_%28book%29 as well as pretty well defining UX "So the job of system designers is to help users form an accurate and useful mental model of a system. And the job of researchers is to set up experiments to learn to understand actual mental models, even though they may be messy and incomplete"
    – PhillipW
    Nov 3 '14 at 20:30
  • 1
    I think the earliest reference which comes to mind is Bartlett (1932) with the War of the Ghosts experiment: asbib.wikia.com/wiki/… The bottom line is the same: what you see is what you THINK you'll see (ie new knowledge depends on existing knowledge).
    – PhillipW
    Nov 3 '14 at 20:45

Regarding the law you are stating in "Mental model law" - I think you are just describing the concept of mental models itself.

My understanding is that a mental model is how the user understands things work, how it actually works is the conceptual model. When users encounter a new system they will base their new mental model(s) on previous experiences.

For example: When I see a door with a flat panel my mental model would be to "push" to open. If the conceptual model matches and it opens then there is less friction in the experience (and I don't walk into the door!)

Where it get's tricky is when there is no previous experience to base the model on. Here you would have to fall back on more fundamental behavior patterns.

For more information check out:

Mental Models: Aligning Design Strategy with Human Behavior (Indi Young)




  • There's a bit more too it than this: the first of those links is the most accurate.
    – PhillipW
    Nov 3 '14 at 12:39

There is no mental model 'law' as such.

Mental Models are a cognitive psychology concept which goes back to the 1940s. Of the articles linked by Sheff I'd read this one:

Susan Weinschenk is a psychologist and gets the detail's right:


This is a useful definition of Mental Models - particularly the bit about 'intuitive perceptions'. (Mental models are always an approximation to reality).

A mental model represents a person’s thought process for how something works (i.e., a person’s understanding of the surrounding world). Mental models are based on incomplete facts, past experiences, and even intuitive perceptions. They help shape actions and behavior, influence what people pay attention to in complicated situations, and define how people approach and solve problems.

Weinschenk however uses the term 'conceptual model' which I just think is a bit confusing ( ie what's the difference between 'mental models and conceptual models' ).

I prefer the term coined by Don Norman in his book The Design of Everyday things (1989) of 'System Image'.

The 'System Image' is basically the representation on screen which the user gets to interact with (see diagram in this article which is taken from Don's book.

Eg: The Graphical User Interface popularised by the early Mac computers (which was where computers were at at in 1989) would have popularised the concept of making the system image look like real world things such as waste baskets, so the 'conceptual model' being got over was that if you put files in the bin then they would have been deleted.

One of the huge failures of this at the time (ie where the designer's idea/ model and the users idea/ model completely failed to line up) was that putting a floppy disk icon in the bin ejected it - rather than deleted its contents...

Mental Models aren't just a label for diagrams, but are a good explanation of how the brain actually processes information and predict how people are seen to perform. Mental models affect how we interact with everything in the world: not just computer interfaces.

If you want to know more about this a specialist cognitive psychology book will give more informaition: Eg

Cognitive Psychology and its Implications J R Anderson



You might be thinking of recognition vs recall

To summarize: recognizing how something works is easy for the user. If the button "sound the alarm" looks like an alarm, this would probably fall into this category. If the user has to recall how something works, it is a lot harder on the users mental resources as well as increasing the risk for failure. Whenever you've opened a product and found yourself thinking "hmm, how did I do this the last time?", then you have a clear case of recall instead of recognition

Further reading: http://www.nngroup.com/articles/recognition-and-recall/

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