Why did Jonas insist on receiving the sunburn memory?

Jonas wanted the memory in order to better understand pain.

Then it ended. He opened his eyes, wincing with discomfort. "It hurt," he told the man, "and I couldn't get the word for it."
"It was sunburn," the old man told him.
"It hurt a lot," Jonas said, "but I'm glad you gave it to me. It was interesting. And now I understand better, what it meant, that there would be pain."