Entitled: "The Disappointment" an old woman interrupts two young lovers; a man peeks through a doorway in the background. Engraving by John Collier, 1773. Human sexual activity, or human sexual practice or human sexual behavior, is the manner in which humans experience and express their sexuality. People engage in a variety of sexual acts from time to time, and for a wide variety of reasons. Sexual activity normally results in sexual arousal and physiological changes in the aroused person, some of which are pronounced while others are more subtle. Voyeurism is the sexual interest in or practice of spying on people engaged in intimate behaviors, such as undressing, sexual activity, or other actions usually considered to be of a private nature.