One of the functions of sati (mindfulness) is to update sañña (perception). Perception is how we know and categorize our sensory data — it tells us what something is or what’s going on in any moment.
Once we acquire language, our perceptions are never completely empty — they are always based on previous data.
It can be helpful to start noticing our perceptions, especially of other people. AND begin to challenge them.
Try this simple practice walking down the street:
Notice people. Notice yourself in response. What thoughts, labels, assumptions, categorizations, and judgments arise? Are they true? How do you know? How did you learn that? Could the opposite be true? Is it? Rinse. Repeat.