They can test this by hooking up sex offenders to a gauge that measures penis volume in response to pictures of naked children and pictures of naked adults.
Is this legal somewhere or are you saying this just happens?
A great many men have some physical attraction to prepubescents -- 50 percent or more.
Is this legal somewhere or are you saying this just happens?
Source?
Penile plethysmography happens a lot for convicted sex offenders, and has also been used with lots of volunteers.
Sources: http://www.ipce.info/ipceweb/Library/97-048_article.html
Sarah Goode addresses the subject, citing several studies in this book:
http://www.amazon.com/Understanding-Addressing-sexual-Attraction-Children/dp/0415446260