What does "mental mold built of beliefs" in this paragraph?
Here is the sentence:
"The first impression becomes an idea of how someone is, like a mental mold built of beliefs, and people then nonconsciously look for confirmation of those initial beliefs while discarding details that might contradict them. Supposedly, we form an opinion of someone during the first three seconds of meeting them. Then, during the following 30 seconds, we shape up that initial impression and try to fit whatever new information that comes up into reinforcing that first impression."
Can you explain the meaning of the expression "mental mold built of beliefs"? Thank!