To discern whether or not emotions are directly linked to facial expressions, psychologist Carney Landis drew lines on volunteers' faces with a burnt cork to easily view the movement of the muscles.

He observed their expressions when they smelled ammonia, listened to jazz, looked at porn and put their hands in a bucket of frogs. The climax of the 1924 experiment was decapitating a live rat. However he didn't find one single expression that linked with the rat massacre.