Why does charlie become angry?

Burt wanted to readminister the inkblot test with Charlie. Charlie believed he was supposed to find pictures in the inkblots and he couldn't. He was angry because he couldn't see any pictures hidden insode of them, but he didn't understand that there weren't really pictures.......

"What do you mean?" I shouted at him. Being so afraid of the inkblots had

made me angry at myself and at Burt too. "That's what you said to me. Just

because you're smart enough to go to college doesn't mean you have to make

fun of me. I'm sick and tired of everybody laughing at me."