Human Sexuality: An Encyclopedia states that 'the inner third of the anal canal is less sensitive to touch than the outer two-thirds, but is more sensitive to pressure' and that 'the rectum is a curved tube about eight or nine inches long and has the capacity, like the anus, to expand'.
Research indicates that anal sex occurs significantly less frequently than other sexual behaviors, but its association with dominance and submission, as well as taboo, makes it an appealing stimulus to people of all sexual orientations. In addition to sexual penetration by the penis, people may use sex toys such as a dildo, a butt plug or anal beads, engage in fingering, anilingus, pegging, anal masturbation or fisting for anal sexual activity, and different sex positions may also be included.
