Here are the 15 stages:

1. Smirk: Slight, often fleeting upturning of the corners of the mouth, completely voluntary and controllable.
2. Smile: Silent, voluntary and controllable, more perceptible than a smirk; begins to release endorphins.
3. Grin: Silent, controllable, but uses more facial muscles (e.g., eyes begin to narrow).
4. Snicker: First emergence of sound with facial muscles, but still controllable (if you hold in a snicker, it builds up gas).
5. Giggle: Has a 50% chance of reversal to avoid a full laugh; sound of giggling is amusing; efforts to suppress it tend to increase its strength.
6. Chuckle: Involves chest muscles with deeper pitch.
7. Chortle: Originates even deeper in the chest and involves muscles of torso; usually provokes laughter in others.
8. Laugh: Involves facial and thoracic muscles as well as abdomen and extremities; sound of barking or snorting.
9. Cackle: First involuntary stage; pitch is higher and body begins to rock, spine extends and flexes, with an upturning of head.
10. Guffaw: Full body response; feet stomp, arms wave, thighs slapped, torso rocks, sound is deep and loud; may result in free flowing of tears, increased heart rate, and breathlessness; strongest solitary laughter experience.
11. Howl: Volume and pitch rise higher and higher and body becomes more animated.
12. Shriek: Greater intensity than howl; sense of helplessness and vulnerability.
13. Roar: Lose individuality; i.e., the audience roars!
14. Convulse: Body is completely out of control in a “fit” of laughter resembling a seizure; extremities flail aimlessly, balance is lost, gasp for breath, collapse or fall off chair.
15. Die Laughing: Instant of total helplessness; a brief, physically intense, transcendent experience; having died, we are thereafter reborn in a refreshing moment of breathlessness and exhaustion with colours more vivid and everything sparkling; everything is renewed.