A mental model is an explanation of someone's thought process about how something works in the real world. It is a representation of the surrounding world, the relationships between its various parts and a person's intuitive perception about his or her own acts and their consequences. Mental models can help shape behaviour and set an approach to solving problems (akin to a personal algorithm) and doing tasks.
A mental model is a kind of internal symbol or representation of external reality, hypothesized to play a major role in cognition, reasoning and decision-making. Kenneth Craik suggested in 1943 that the mind constructs "small-scale models" of reality that it uses to anticipate events.
Jay Wright Forrester defined general mental models as:
"The image of the world around us, which we carry in our head, is just a model. Nobody in his head imagines all the world, government or country. He has only selected concepts, and relationships between them, and uses those to represent the real system."
In psychology, the term "mental models" is sometimes used to refer to mental representations or mental simulation generally. At other times it is used to refer to mental models and reasoning and to the mental model theory of reasoning developed by Philip Johnson-Laird and Ruth M.J. Byrne.
The term "mental model" is believed to have originated with Kenneth Craik in his 1943 book The Nature of Explanation. Georges-Henri Luquet in Le dessin enfantin (Children's Drawings), published in 1927 by Alcan, Paris, argued that children construct internal models, a view that influenced, among others, child psychologist Jean Piaget.
Philip Johnson-Laird published Mental Models: Towards a Cognitive Science of Language, Inference and Consciousness in 1983. In the same year, Dedre Gentner and Albert Stevens edited a collection of chapters in a book also titled Mental Models. The first line of their book explains the idea further: "One function of this chapter is to belabor the obvious; people's views of the world, of themselves, of their own capabilities, and of the tasks that they are asked to perform, or topics they are asked to learn, depend heavily on the conceptualizations that they bring to the task." (see: Mental Models (Gentner-Stevens book)).
Since then, there has been much discussion and use of the idea in human-computer interaction and usability by researchers including Donald Norman and Steve Krug (in his book Don't Make Me Think). Walter Kintsch and Teun A. van Dijk, using the term situation model (in their book Strategies of Discourse Comprehension, 1983), showed the relevance of mental models for the production and comprehension of discourse.
Mental models and reasoning 
One view of human reasoning is that it depends on mental models. In this view, mental models can be constructed from perception, imagination, or the comprehension of discourse (Johnson-Laird, 1983). Such mental models are akin to architects' models or to physicists' diagrams in that their structure is analogous to the structure of the situation that they represent, unlike, say, the structure of logical forms used in formal rule theories of reasoning. In this respect, they are a little like pictures in the "picture" theory of language described by philosopher Ludwig Wittgenstein in 1922. Philip Johnson-Laird and Ruth M.J. Byrne developed a theory of mental models which makes the assumption that reasoning depends, not on logical form, but on mental models (Johnson-Laird and Byrne, 1991).
Principles of mental models 
Mental models are based on a small set of fundamental assumptions (axioms), which distinguish them from other proposed representations in the psychology of reasoning (Byrne and Johnson-Laird, 2009). Each mental model represents a possibility. A mental model represents one possibility, capturing what is common to all the different ways in which the possibility may occur (Johnson-Laird and Byrne, 2002). Mental models are iconic, i.e., each part of a model corresponds to each part of what it represents (Johnson-Laird, 2006). Mental models are based on a principle of truth: they typically represent only those situations that are possible, and each model of a possibility represents only what is true in that possibility according to the proposition. However, mental models can represent what is false, temporarily assumed to be true, for example, in the case of counterfactual conditionals and counterfactual thinking (Byrne, 2005).
Reasoning with mental models 
People infer that a conclusion is valid if it holds in all the possibilities. Procedures for reasoning with mental models rely on counter-examples to refute invalid inferences; they establish validity by ensuring that a conclusion holds over all the models of the premises. Reasoners focus on a subset of the possible models of multiple-model problems, often just a single model. The ease with which reasoners can make deductions is affected by many factors, including age and working memory (Barrouillet, et al., 2000). They reject a conclusion if they find a counterexample, i.e., a possibility in which the premises hold, but the conclusion does not (Schroyens, et al. 2003; Verschueren, et al., 2005).
Scientific debate continues about whether human reasoning is based on mental models, versus formal rules of inference (e.g., O'Brien, 2009), domain-specific rules of inference (e.g., Cheng & Holyoak, 2008; Cosmides, 2005), or probabilities (e.g., Oaksford and Chater, 2007). Many empirical comparisons of the different theories have been carried out (e.g., Oberauer, 2006).
Mental models in system dynamics 
A mental model is generally:
- founded on hardly qualifiable, impugnable, obscure, or incomplete facts
- flexible – is considerably variable in positive as well as in negative sense
- effects as information filter[disambiguation needed] – causes selective perception, perception of only selected parts of information
- compared with the complexities surrounding the world, it is very limited, and even when the scientific model is extensive and in accordance with a certain reality in the derivation of logical consequences of it. It must take into account such restrictions on working memory; i.e., well-known rules on the maximum number of elements that people are suddenly able to remember, gestaltismus or failure of the principles of logic, etc.
- sources of information, which one can not find anywhere else, are available at any time and can be used.
Mental models are a fundamental way to understand organizational learning. Mental models are "deeply held images of thinking and acting." Mental models are so basic to understanding of the world that people are hardly conscious of them.
Expression of mental models 
Three basic forms are typically used: 
- Polygons – whose vertices sharing the edge represent related items.
- Causal-loop diagrams – displaying tendency and a direction of information connections and the resulting causality
- Flow diagrams[disambiguation needed] – a more appropriate way to express a dynamic system.
Those forms allow showing a mental model, as a written model, which can help remember more details, such as more items in a long list.
Mental model in relation to system dynamics and systemic thinking 
These two disciplines can help to construct a better coordination with the reality of mental models and simulate it accurately. They increase the probability that the consequences of how to decide and act in accordance with how to plan.
- System dynamics – extending mental models through the creation of explicit models, which are clear, easily communicated and can be compared with each other.
- Systemic thinking – seeking the means to improve the mental models and thereby improve the quality of dynamic decisions that are based on mental models.
Single and double-loop learning 
After analyzing the basic characteristics, it is necessary to bring the process of changing the mental models, or the process of learning. Learning is a back-loop process, and feedback loops can be illustrated as: single-loop learning or double-loop learning.
Single-loop learning 
Mental models affect the way people work with the information and determine the final decision. The decision itself changes, but the mental models remain the same. It is the predominant method of learning, because it is very convenient. One established mental model is fixed, so the next decision is very fast.
Double-loop learning 
A double-loop process (see diagram below) is used when it is necessary to change the mental model on which a decision depends. Unlike single loops, this model includes a shift in understanding, from simple and static to broader and more dynamic, such as taking into account the changes in the surroundings and the need for expression changes in mental models.
|Process of learning|
See also 
- "Mental models", report at www.lauradove.info.
- Šusta, Marek. "Několik slov o systémové dynamice a systémovém myšlení" (PDF) (in Czech). Proverbs, a.s. pp. 3–9. Retrieved 2009-01-15.
- Mildeova, S., Vojtko V. (2003). Systémová dynamika (in Czech). Prague: Oeconomica. pp. 19–24. ISBN 80-245-0626-2.
- Ford, David N., Sterman, John D. "Expert Knowledge Elicitation to Improve Mental and Formal Models" (PDF). Cambridge, Massachusetts, USA - Massachusetts Institute of Technology. pp. 18–23. Retrieved 11.1.2009.
- "LEADING FOR A CHANGE", Ralph Jacobson, 2000, Chapter 5, Page102
- Barrouillet, P. et al. (2000). Conditional reasoning by mental models: chronometric and developmental evidence. Cognit. 75, 237-266.
- Byrne, R.M.J. (2005). The Rational Imagination: How People Create Counterfactual Alternatives to Reality. Cambridge MA: MIT Press.
- Byrne, R.M.J. & Johnson-Laird, P.N. (2009). 'If' and the problems of conditional reasoning. Trends in Cognitive Sciences. 13, 282-287
- Cheng, P.C. and Holyoak, K.J. (2008) Pragmatic reasoning schemas. In Reasoning: studies of human inference and its foundations (Adler, J.E. and Rips, L.J., eds), pp. 827–842, Cambridge University Press
- Cosmides, L. et al. (2005) Detecting cheaters. Trends in Cognitive Sciences. 9,505–506
- Oberauer K. (2006) Reasoning with conditionals: A test of formal models of four theories. Cognit. Psychol. 53:238–283.
- O’Brien, D. (2009). Human reasoning includes a mental logic. Behav. Brain Sci. 32, 96–97
- Oaksford, M. and Chater, N. (2007) Bayesian Rationality. Oxford University Press
- Johnson-Laird, P.N. (1983). Mental Models: Towards a Cognitive Science of Language, Inference, and Consciousness. Cambridge: Cambridge University Press.
- Johnson-Laird, P.N. (2006) How We Reason. Oxford University Press
- Johnson-Laird, P.N. and Byrne, R.M.J. (2002) Conditionals: a theory of meaning, inference, and pragmatics. Psychol. Rev. 109, 646–678
- Schroyens, W. et al. (2003). In search of counterexamples: Deductive rationality in human reasoning. Quart. J. Exp. Psychol. 56(A), 1129–1145.
- Verschueren, N. et al. (2005). Everyday conditional reasoning: A working memory-dependent tradeoff between counterexample and likelihood use. Mem. Cognit. 33, 107-119.
Further reading 
- Georges-Henri Luquet (2001). Children's Drawings. Free Association Books. ISBN 1-85343-516-3
- Groesser, S.N. (2012). Mental model of dynamic systems. In N.M. Seel (Ed.). The encyclopedia of the sciences of learning (Vol. 5, pp. 2195-2200). New York: Springer.
- Groesser, S.N. & Schaffernicht, M. (2012). Mental Models of Dynamic Systems: Taking Stock and Looking Ahead. System Dynamics Review, 28(1): 46-68, Wiley.
- Johnson-Laird, P.N. 2005. The History of Mental Models
- Johnson-Laird, P.N., 2005. Mental Models, Deductive Reasoning, and the Brain
- Jones, N. A. et al. (2011). "Mental Models: an interdisciplinary synthesis of theory and methods" Ecology and Society.16 (1): 46.
- Robles-De-La-Torre, G. & Sekuler, R. (2004). "Numerically Estimating Internal Models of Dynamic Virtual Objects". In: ACM Transactions on Applied Perception 1(2), pp. 102–117.
- Sterman, John D. A Skeptic’s Guide to Computer Models, Massachusetts Institute of Technology