According to FBI agent Ken Lanning, "collecting" pornography does not mean that they merely view pornography, but that they save it, and "it comes to define, fuel, and validate their most cherished sexual fantasies". Lanning states that the collection is the single best indicator of what the offender wants to do, but not necessarily of what has been or will be done. Researchers Taylor and Quayle reported that pedophilic collectors of child pornography are often involved in anonymous internet communities dedicated to extending their collections. Causes
Although what causes pedophilia is not yet known, researchers began reporting a series of findings linking pedophilia with brain structure and function, beginning in 2002. Testing individuals from a variety of referral sources inside and outside the criminal justice system as well as controls, these studies found associations between pedophilia and lower IQs, poorer scores on memory tests, greater rates of non-right-handedness, greater rates of school grade failure over and above the IQ differences, being below average height, greater probability of having had childhood head injuries resulting in unconsciousness, and several differences in MRI-detected brain structures.Such studies suggest that there are one or more neurological characteristics present at birth that cause or increase the likelihood of being pedophilic. Some studies have found that pedophiles are less cognitively impaired than non-pedophilic child molesters. A 2011 study reported that pedophilic child molesters had deficits in response inhibition, but no deficits in memory or cognitive flexibility.
He wrote that he had only encountered it four times in his career and gave brief descriptions of each case, listing three common traits:

The individual is tainted [by heredity] (hereditär belastete)
The subjects primary attraction is to children, rather than adults. The acts committed by the subject are typically not intercourse, but rather involve inappropriate touching or manipulating the child into performing an act on the subject.He mentions several cases of pedophilia among adult women (provided by another physician), and also considered the abuse of boys by homosexual men to be extremely rare. Further clarifying this point, he indicated that cases of adult men who have some medical or neurological disorder and abuse a male child are not true pedophilia and that, in his observation, victims of such men tended to be older and pubescent. He also lists pseudopaedophilia as a related condition wherein "individuals who have lost libido for the adult through masturbation and subsequently turn to children for the gratification of their sexual appetite" and claimed this is much more common.Austrian neurologist Sigmund Freud briefly wrote about the topic in his 1905 book Three Essays on the Theory of Sexuality in a section titled The Sexually immature and Animals as Sexual objects. He wrote that exclusive pedophilia was rare and only occasionally were prepubescent children exclusive objects.