The changeable nature of models is considered a limitation because when the model changes, the answers that were concluded from the model may also change. This means that conclusions drawn from changeable models may be true at a certain time, place or circumstance, but the conclusions are not necessarily objectively true.
Scientists use models to demonstrate and understand anything from human behavior to molecular behavior. The models make difficult concepts easier to be visualized and understood, and they often reference very commonly accepted knowledge. Models can be represented graphically, mathematically or conceptually.
Models used in the hard sciences such as biology, chemistry, and physics often demonstrate permanent observations and conclusions. However, models that are used in social sciences are not always as static because human behavior and culture is always changing and evolving. Technology, new discoveries, new forms of communication and global events all contribute to a changing of human behavior and sentiment. Humans today think and act significantly differently than they did 100 years ago. For this reason, many consider the changeable nature of models to be a limitation in the attempt to model human behavior. When humans change, the model must change, and therefore conclusions made from the previous models are no longer necessarily true.