Symptoms that help distinguish a true orgasm from a sham:

Breathing quickens, becomes deep and intermittent. Before the climax, the vagina contracts, tightly clasping the cock in a ring. Before the cherished denouement, there is always an abundant release of vaginal lubrication. The face and neck turn red with excitement, the eyes close or roll back. The body and limbs may make unusual movements that resemble convulsions. Someone utters inarticulate sounds, others swear or just moan.