SCHEMATA
A schema (pl. schemata or schemas), is a mental structure that represents some aspect of the world. People use schemata to organize current knowledge and provide a framework for future understanding.
Schemata influence our attention, as we are more likely to notice things that fit into our schema. If something contradicts our schema, it may be encoded or interpreted as an exception or as unique. Thus, schemata are prone to distortion. They influence what we look for in a situation. They have a tendency to remain unchanged, even in the face of contradictory information. We are inclined to place people who do not fit our schema in a "special" or "different" category, rather than to consider the possibility that our schema may be faulty. As a result of schemata, we might act in such a way that actually causes our expectations to come true.
Schemata can influence and hamper the uptake of new information (proactive interference), such as when existing stereotypes, giving rise to limited or biased discourses and expectations (prejudices), may lead an individual to "see" or "remember" something that has not happened because it is more believable in terms of his/her schema. For example, if a well-dressed businessman draws a knife on a vagrant, the schemata of onlookers may (and often do) lead them to "remember" the vagrant pulling the knife. Such distortion of memory has been demonstrated.
A schema for oneself is called a "self schema". Schemata for other people are called "person schemata". Schemata for roles or occupations are called "role schemata", and schemata for events or situations are called "event schemata" (or scripts).
Modification of Schemata
New information that falls within an individual's schema is easily remembered and incorporated into their worldview. However, when new information is perceived that does not fit a schema, many things can happen. The most common reaction is to simply ignore or quickly forget the new information. This can happen on a deep level—frequently an individual does not become conscious of or even perceive the new information. However, when the new information cannot be ignored, existing schemata must be changed.
Assimilation is the reuse of schemata to fit the new information. For example, when an unfamiliar dog is seen, a person will probably just assimilate it into their dog schema. However, if the dog behaves strangely, and in ways that don't seem dog-like, there will be "accommodation" as a new schema is formed for that particular dog.