Viewers of child pornography who are pedophiles are particularly obsessive about collecting, organizing, categorizing, and labeling their child pornography collection according to age, gender, sex act and fantasy.[61][62] 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." An extensive collection indicates a strong sexual preference for children, and if a collector of child pornography is also a pedophile, the owned collection is the single best indicator of what he or she wants to do.[62] The National Society for the Prevention of Cruelty to Children describes researchers Taylor and Quayle's analysis of pedophile pornography collecting: