An animal hoarder keeps an unusually large number of pets, but fails to care for them properly. A hoarder is distinguished from an animal breeder, who would have a large number of animals as the central component of his or her business; this distinction can be problematic, however, as some hoarders are former breeders who have ceased selling and caring for their animals, while others will claim to be breeders as a psychological defense mechanism, or in hopes of forestalling intervention. Gary Patronek, director of the Center for Animals and Public Policy at Tufts University, defines hoarding as the "pathological human behavior that involves a compulsive need to obtain and control animals, coupled with a failure to recognize their suffering". According to another study, the distinguishing feature is that a hoarder "fails to provide the animals with adequate food, water, sanitation, and veterinary care, and... is in denial about this inability to provide adequate care." Along with other compulsive hoarding behaviours, it is linked in the DSM-IV to obsessive compulsive disorder and obsessive compulsive personality disorder. Alternatively, animal hoarding could be related to addiction, dementia, or even focal delusion.