Combining these two ideas, she now understands the purpose of the mixture control is to keep these two quantities in balance as the  aircraft changes altitude. “Mental model” or self-explanation is often used to refer to an organized collection of ideas that forms a  learner’s understanding of a thing or process.$_{ }$ The advantages of possessing this type of understanding include the following:  3. Understanding shared between people allows them to communicate more efficiently. For example, an  experienced pilot might mention to an experienced mechanic that a magneto ran a bit rough during an  engine run-up. This brief communication triggers access to a wealth of knowledge in the mind of the  mechanic who instantly knows what to do.  2. Learners who understand a process have an easier time mastering variations of the processes, such as  unfamiliar aircraft, new avionics systems, and unfamiliar airport procedures.  1. The learner is no longer limited to answering questions that match the memorized facts. For example,  armed with the understanding of the mixture control, Beverly may now be able to produce answers to more  challenging questions, such as what would happen if the mixture were set too rich or too lean.  3-10  Figure 3-6.  A learner acquires knowledge through memorization, understanding, and application. 