Eto Demerzel laughed.
    It was not the first time. He sat there, with Hari Seldon and Dors Venabili in a tap-free room, and, every once in a while, at a signal from Hari, he would laugh. Sometimes he leaned back and laughed uproariously, but Seldon shook his head. "That would never sound convincing."
    So Demerzel smiled and then laughed with dignity and Seldon made a face. "I'm stumped," he said. "It's no use trying to tell you funny stories. You get the point only intellectually. You will simply have to memorize the sound."
    Dors said, "Use a holographic laughtrack."
    "No! That would never be Demerzel. That's a bunch of idiots being paid to yak. It's not what I want. Try again, Demerzel."
    Demerzel tried again until Seldon said, "All right, then, memorize that sound and reproduce it when you're asked the question. You've got to look amused. You can't make the sound of laughing, however proficient, with a grave face. Smile a little, just a little. Pull back the corner of your mouth." Slowly Demerzel's mouth widened into a grin. "Not bad. Can you make your eyes twinkle?"
    "What do you mean, 'twinkle,"' said Dors indignantly. "No one makes their eyes twinkle. That's a metaphorical expression."
    "No, it's not," said Seldon. "There's the hint of tears in the eye-sadness, joy, su............