Sexual intercourse or other sexual activity can encompass various sexually stimulating factors (physiological stimulation or psychological stimulation), including different sex positions (such as the missionary position, the most common human sex position) or the use of sex toys. Foreplay may precede some sexual activities, often leading to sexual arousal of the partners and resulting in the erection of the penis or natural lubrication of the vagina. It is also common for people to be as sexually satisfied by being kissed, touched erotically, or held as they are by sexual intercourse.