The initial origins of Hypodermic Theory are largely unknown, and research on the theory's founder is hampered by the generality that surrounded media analysis in the early decades of the 20th century. Hypodermic Theory, also known as "Magic Bullet Theory" and "Hypodermic Needle Theory" seems to have arisen out of the glut of propaganda and other persuasive films made public in the years immediately after World War I and in the several years leading up to World War II. Although he is not widely recognized as the original theorist, Harold Lasswell may have refined and introduced Hypodermic Theory in his 1927 book, "Propaganda Technique in the World War." As media trends changed, however, and the understanding of broadcast effects matured, the communications industry largely moved away from Hypodermic Theory in favor of belief in a more dynamic and intelligent audience.
The characteristic premise of Hypodermic Theory is that communication, like a hypodermic needle, injects a message directly into a receiver. The receiver will then wholly accept the message and respond in a predictable pattern.
Although its exact origin remains unknown, Hypodermic Theory appears to have risen to prominence in the 1920s. It enjoyed nearly full acceptance during the 1930s and 1940s before being largely discredited by advanced theorists in the 1950s.
Despite its questionable validity, Hypodermic Theory was applied liberally during the lead-up to World War II. Perhaps one of the most famous applications of the theory, the Nazi propaganda film "Triumph of the Will" is still studied by communications students and professors alike for its mesmerizing call to dutiful service. Another famous application of the theory came during the 1938 broadcast of War of the Worlds; as listeners believed the story they were hearing, their ensuing panic and disparity seemed to reinforce the concepts of Hypodermic Theory.
During the early years of mass broadcast, and even through the 1940s, Hypodermic Theory appeared to hold true. Certainly, the propaganda displayed by all sides during and immediately before World War II seemed to reinforce the theory, persuading receivers of messages to follow an intended pattern of compliance and support. As the war passed and studies of communication proceeded into more advanced fields, Hypodermic Theory became largely discredited. One of the larger contributions to the downfall of Hypodermic Theory was research conducted by Marshall McLuhan; his theories about "the medium is the message" and other communication concepts opened the door to an advanced understanding of a learning, growing and changing media market.