In 1924, psychologist Carney Landis wanted to find out if all humans made the same facial expressions in response to the same emotions, so he captured photos of his subjects after unpleasant experiences, like being shocked with electricity or putting their hands inside a bucket full of frogs. Worst of all, he ordered his subjects to decapitate a live rat — and if they refused to cut off the rodent's head, Landis would do it himself and force the person to watch. And in the end, for all the traumatic experiences that Landis' subjects endured, the conclusion of his experiment was anticlimactic. Landis ultimately found that the natural expressions people made in response to pain, disgust, and horror "showed great differences among themselves. In some cases where it was expected, no expression of emotion was present at all."