Young children are unable to determine that an equivalent volume of liquid is equivalent, even when they see it poured directly from one vessel to another.
They also cannot understand that an object concealed by the box must be behind (or under) the box.
There are other cases. Skinner tried to ascribe certain pigeon behaviors associated with random reinforcement to superstition, though others disagree about whether that fits the bill.
Tell a man he’s a guard, or a prisoner, and he will see the experimental world quite differently.
Tell a man he’s got to continue with electric shocks, he sees the world quite differently.
Bill Hicks did a bit in the wake of the trial of the LAPD police officers who were filmed hitting Rodney King Jr. He said something like:
[The officer] looks in the camera and actually says, “Oh, that Rodney King beating tape, it’s all in how you look at it.”
“All in how you look at it, officer […]?”
“That’s right, it’s how you look at the tape.”
“Well, would you care to tell the court how you’re looking at that?”
“Yeah, okay, sure. It’s how you look at it. The tape. For instance, well, if you play it backwards, you see us help King up and send him on his way.”
While Hicks was just making fun of what he saw as a completely ridiculous verdict and trial, the reality of different people looking at the same thing is often nearly this stark.
Eyewitness testimony is far less reliable than you might think.
There was a case study done in 1954, They Saw a Game, by Hasdorf and Cantril. They showed footage of a rough 1951 collegiate American football game between the Dartmouth Indians and the Princeton Tigers to psychology students of the two schools. A week later, the students filled out questionnaires about the game.
There were major discrepancies between the perceptions of the game by students of one school and the other. Effectively, they watched a different game, owing the difference entirely to their perception of the action.
The difference of perception between minds is extraordinary. It is especially relevant these days, between the ongoing anger over perceived grievances against the West, the ongoing anger over disagreements in politics, the ongoing anger over the ongoing financial crises.
You have antagonists that see opportunities in conflict. This includes religious groups that raise funds based on the urgency of religious turmoil. It includes news organizations that make a living off of feeding perception differences. It includes political organizations that feed off the fear of the different perceivers gaining power. It is important to note that they aren’t necessarily aware of their exploitation of the conflict; many honestly believe in the urgency of their cause.
You have people trying to honestly highlight the underlying causes and realities of the conflicts. These are attacked for their trouble, by the partisans who believe they are trying to undermine the cause.
And you have the majority, who are too busy with other things. They perceive conflicts as intractable, beyond understanding.