In modern sexology, researchers apply tools from several academic fields, such as biology, medicine, psychology, epidemiology, sociology and criminology. Sexologists study sexual development (puberty), sexual orientation, sexual relationships and sexual activity, as well as document the sexualities of special groups; for example, child sexuality, adolescent sexuality, sexuality among the elderly and the disabled. The sexological study of sexual dysfunctions and disorders, including erectile dysfunction, anorgasmia, and pedophilia, are also common.