Cognitive psychology developed the concept of schema (plural: schemas or schemata) to describe "a pattern of thought or behavior that organizes categories of information and the relationships among them". According to Kendray Cherry's article What Is a Schema in Psychology?,
A schema is a cognitive framework or concept that helps organize and interpret information. Schemas can be useful because they allow us to take shortcuts in interpreting the vast amount of information that is available in our environment.
So far, so good, but the availabiliity of these concepts and shortcuts comes at a price (my emphasis):
However, these mental frameworks also cause us to exclude pertinent information to focus instead only on things that confirm our pre-existing beliefs and ideas. Schemas can contribute to stereotypes and make it difficult to retain new information that does not conform to our established ideas about the world.
We have schemas for things, person schemas, social schemas, self-schemas and event schemas. With regard to their role, Kendra Cherry points out that schemas influence what we pay attention to, that they help simplify the world, that they allows us to think quickly, that they can chage they way we interpret incoming information and that they can be remarkably difficult to change.
The use of schemas is typically automatic. One potential problem related to schemas is prejudice. Kendra Cherry mentions a study related to gender expectations and stereotypes:
In one interesting study, researchers showed children images that were either consistent with gender expectations (such as a man working on a car and woman washing dishes) while others saw images that were inconsistent with gender stereotypes (a man washing dishes and a woman fixing a car).
When later asked to remember what they had seen in the images, children who help very stereotypes views of gender were more likely to change the gender of the people they saw in the gender-inconsistent images. For example, if they saw an image of a man washing dishes, they were more likely to remember it as an image of a woman washing dishes.
A related concept is that of a perceptual set. In the article Definition and Examples of Perceptual Sets in Psychology, Kendra Cherry defines the concept as follows:
A perceptual set refers to a predisposition to perceive things in a certain way. In other words, we often tend to notice only certain aspects of an object or situation while ignoring other details.
She adds that "the way you see the world is heavily influenced (and biased) by your own past experiences, expectations, motivations, beliefs, emotions, and even your culture?" Later in the article, Cherry also mentions schemas, which contribute to these perceptual sets. She gives the following examples of schemas that influence perceptual sets:
For example, people have a strong schema for faces, making it easier to recognize familiar human faces in the world around us. It also means that when we look at an ambiguous image, we are more likely to see it as a face than some other type of object.
Psychologists and other disciplines that study how we think (e.g. philosophy) have identified many biases; Wikipedia's list of cognitive biases is depressingly long. In the context of the current question, biases related to belief and social biases are interesting. Wikipedia also has a separate list of memory biases.
Schemas, perceptual sets and biases all influence the way we write texts and how we interpret them. Moreover, they do this automatically and subconsciously. Since these biases can cause reasoning errors, several disciplines are studying how to reduce or mitigate them; see e.g. cognitive bias mitigation and cognitive bias modification on Wikipedia.
So in everything that we meaningfully call a text (this excludes "1 + 1 = 2" from the other response), bias will unavoidably creep in. We can mitigate it somewhat by having the text reviewed by other people, especially people who don't share all of our biases and who are aware of many existing cognitive biases.
