Mental models are a very important concept to understand in the process of personal and organizational learning. To be able to learn it is necessary to understand out deeper beliefs. Only when we understand our deeper beliefs we will be able to change them and become learning people. The deeper beliefs described here is what Senge (1990) means with a mental model.
Mental models are simplifications (models) of a whole community, organization or for example a family. In our head we do not carry all the information about this group but we carry images, assumptions and stories (Senge, 1990). With the use of mental models we are able understand the world around us and decide on how to take action. Since the mental models in our head of a certain situation will "explain" what is going on this seems logic. In times of pressure our mental models will explain what is going on and allow is to cope with the situation.
Therefore the mental models are sometimes explained to show the theory in use.
Theory in use and espoused theory are two different things. The second one is what we say as on how we will behave in a certain situation. When at the moment that we are in this situation this may not be necessarily true. It might be possible that our theory in use deviates from our espoused theory because of deeper held beliefs. Those beliefs are the mental models. An example of such a situation can be when you have an espoused theory that says that cooperation between different members of a company is important to increase the total welfare of the company. During stress though you might react in a totally different way, using your authority to command every person in the company, because...