When Stanley discovered Livingstone, he was invited to a celebratory dinner at one of the tribes that Livingstone was ministering to, the Krai tribe.
As part of the festivities, several dances and acts were performed. Part of one of these acts involved a man coming out and imitating a hunt, but in the hunt story, the man doing the hunter was wounded by a 'lion' and began to make moaning noises as if in pain.
As soon as he began to make the noise, Livingstone covered his face with his hands, and then, when that part of the act was over, he took his hands away and watched the rest as normal.
Stanley was curious about this, and when talking about the performance later, asked him why he covered his face. "Was it offensive in some way?"
"No", replied Livingstone, "it's just that I can't stand to see a Krai man groan."