Each year about 40 percent of teens and preteens visit sexually explicit sites either deliberately or accidentally, studies here and abroad show. In a study in the February Pediatrics (Vol. 119, No. 2, pages 247-257), for example, attorney Janis Wolak, psychologist Kimberly Mitchell, PhD, and Finkelhor, of the UNH center, found that 42 percent of a nationally representative sample of 1,500 Internet users ages 10 to 17 had been exposed to online porn in the last year, with two-thirds reporting only unwanted exposure. In fact, the incidence of unwanted exposure has risen for this age group, from about 26 percent between 1999 and 2000, to 34 percent in 2005, the team has found.
Perhaps not surprisingly, boys are much more likely to seek out pornography than girls, and use increases with age, research finds. In the UNH team's study, for instance, 38 percent of 16- and 17-yea-rold male Internet users deliberately visited X-rated sites in the past year, compared with 8 percent of girls. Similarly, Australian sociologist Michael Flood, PhD, of La Trobe University, reported in the March issue of the Journal of Sociology (Vol. 43, No. 1, pages 45-60) that 38 percent of boys and 2 percent of girls ages 16 and 18 deliberately accessed such material.
http://www.apa.org/monitor/nov07/webporn.aspx