Franz Clemens Brentano (1838--1917) developed a theory of judgment that was concerned with what happens in our minds when judgments are being made. Brentano's theory proposes that the act of judging is what entails the truth and not the object that we are making a judgment about. For judgments to take place, there needs to be an object presented, whether physical or nonphysical. The judgments that arise can be positive or negative depending on whether you accept or reject the object as existing. Judgments are arrived at by forming expressions such as A exists or A does not exist.
Emmanuel Kant, a 19th-century philosopher, proposed that our capacity to form judgments is the most important aspect of the human mind. The human mind has the capacity to create objective representations of what we are judging. The judgments that we make are meaningful and true only to the extent that they adhere to his transcendental idealism theory. According to this theory, objects are not things in themselves; they do not stand alone from our mind processes. Objects (physical or nonphysical) are representation of the mind and what the mind judges them to be.
The social judgment theory, as proposed by Muzafer Sherif and Carl Hovland, describes how we perceive and judge the information that we receive. There are three positions that people take upon receiving a piece of information: accept, reject or remain noncommitted (or neutral). People make these judgments based on their "anchor position"-- the position that represents their values, principles and truths. Information is then accepted or rejected, or the person making the judgment stays neutral, depending on how close the information is to the anchor position.
The heuristic judgment theory by Daniel Kahneman and Amos Tversky proposes that people use certain familiar mental shortcuts (heuristics) to simplify their judgments. The representativeness heuristic is when certain object is judged to the extent that it represents the core characteristics of the group that it belongs to. The availability heuristic is when people make judgments based on likely events that come to mind easily because of their impact or their familiarity. And the anchoring and adjustment heuristic is used when people are deciding on whether to change from their original positions; people adjust slowly and only to the extent that their anchor position may face failure.