One of the main focuses of modern psychological humour theory and research is to establish and clarify the correlation between humour and laughter. The major empirical findings here are that laughter and humour do not always have a one-to-one association. While most previous theories assumed the connection between the two almost to the point of them being synonymous, psychology has been able to scientifically and empirically investigate the supposed connection, its implications, and significance.
In 2009, Diana Szameitat conducted a study to examine the differentiation of emotions in laughter. They hired actors and told them to laugh with one of four different emotional associations by using auto-induction, where they would focus exclusively on the internal emotion and not on the expression of laughter itself. They found an overall recognition rate of 44%, with joy correctly classified at 44%, tickle 45%, schadenfreude 37%, and taunt 50%.:399 Their second experiment tested the behavioural recognition of laughter during an induced emotional state and they found that different laughter types did differ with respect to emotional dimensions.:401–402 In addition, the four emotional states displayed a full range of high and low sender arousal and valence.