Laughter fits can be described as the experience of uncontrollable, intense, and spontaneous laughter which continue to occur despite a lack of any identifiable trigger or a feeling of humorousness. The physical action itself typically consists of rhythmical, often audible contractions of the diaphragm and other parts of the respiratory system. At higher levels, laughter fits can make it extremely difficult to function due to crying and a difficulty talking or keeping one's eyes open. Laughter fits are often accompanied by other coinciding effects such as an increased sense of humour and emotion enhancement. They are most commonly induced under the influence of moderate dosages of psychedelic and dissociative compounds, such as LSD, psilocybin, and nitrous oxide.