Stereotypes are over-generalized judgments about particular groups of people, a set of qualities that all people from these groups are expected to exhibit. Stereotypes are socially developed, and every person would be able to name a list of stereotypes attributed to a group, whether they personally believe it or not (for example, all Asians are good in math).
Even when you do not believe that some stereotype may be true, it is very possible that it subconsciously influences your judgment of a person from a specific group when you meet them for the first time. What happens then, your brain starts evaluation and comparison of a person’s behavior against expectations based on stereotypes. Here, two things make the evaluation more biased – confirmation bias and predictive brain theory.