The year before he had also founded the Parapsychology Institute of America and for over two decades beginning in 1974 was a popular lecturer in parapsychology for the New York City Board of Education, Forest Hills Adult Division. He initially attained some level of fame in the mid-1970s when he investigated the reported haunting of a house on Long Island at Amityville, New York. Although the Amityville haunting was promoted in several books and a popular movie, Kaplan was the first to denounce it as a hoax, a view now generally accepted in the parapsychological community. Further accounts of his parapsychological endeavors can be found in the several volumes of True Tales of the Unknown and a number of other descriptive works on psychical research.
In Kaplan's first book, Pursuit of Premature Gods and Contemporary Vampires, which appeared in 1976, he treated vampirology as a branch of parapsychology, that branch of psychology dealing with paranormal experiences. He begins with the idea that some reality may lie behind every myth or legend, in this case vampires.
Although he had lectured around the country and appeared on many talk shows over the previous decade, many people first heard of Kaplan in 1984 with the publication of his second book, Vampires Are. The book described a decade of research on people who defined themselves as real vampires. After obtaining a telephone listing for the Vampire Research Center, Kaplan began to receive phone calls from people claiming to be vampires, and he later interviewed some of them personally. In this manner he was able to build relationships with what became a network of people with similar interests around the world. These contacts increased dramatically after a mention in a 1977 Playboy Magazine article. He also began to receive calls about vampire attacks from people who claimed to have been victimized.
Kaplan's research led him to reformulate his concept of vampires, abandoning the common notion that they are the "undead" and have returned to take blood from the living. The vampires he discovered were otherwise normal living people who felt a need to drink blood every day and who became irritable, aggressive, or frantic if they were unable to get their daily supply. Underlying their need was a strong belief that blood kept them youthful and extended their life; if their supply were cut off, they believed they would age or even die. The number of vampires Kaplan interviewed who fit this description was quite small. He reported meeting fewer than 10 by the time his book appeared in 1984, and to date the great majority of people who are either reported to the center as vampires or themselves claim to be vampires fit into a much larger category, the "vampirelike" people. The vampirelike people are individuals who adopt vampire-associated habits (e.g., they sleep in a coffin, wear black clothes, work at night, or occasionally drink blood) in the hope of possibly becoming a vampire. Some are sexually aroused by blood and the idea of drinking it.
In 1981 Kaplan conducted the first official vampire census. Of some 480 questionnaires distributed, 31 were returned and 12 fit the description of a true vampire. Additionally, nine letters were received without the questionnaire from people deemed to be true vampires. Thus, 21 vampires were reported in the census. Kaplan concluded that there were probably many more. In the meantime, apart from the formal census, he was contacted by phone and mail by other people whom he noted to be vampires. A follow-up study in 1983 found 35 additional vampires. Given the number he had been able to locate through his census and other contacts, he estimated there were 150 to 200 actual vampires in North America. By 1992 he projected an estimated 850 vampires worldwide, of which 40 lived in California.
As a result of some negative response to his book, and deteriorating relationships with the leaders of the vampire organizations in the New York City areas, Kaplan largely separated himself from other vampire-oriented organizations. He subsequently devoted himself to his research and thus has had little time for vampire fans. Dr Kaplan created one short film, in 1994 concerning the Stuart House haunting. Dr. Kaplan died in 1995.