When I was studying a few years back, in my school textbook I came across this wonderful quote above. I can't remember who wrote it but the analogy stuck with me.
Some people perceive the world to be black and white, and once they believe something, nothing else can be true. Don't ever think about challenging them because they won't budge!
Other more open minded folks, will always question what they hear. Whether the information came from a teacher, family member or the government. I call this a gray thinker.
Maybe we are just humans and our brain develops in different ways, or maybe it's something more sinister.