DIFFUSION THEORIES(1963) indicated, the drug studies truly represent-
ed an independent replication of the principles of
innovation diffusion developed by rural sociolo-
gists because the public health researchers were
unaware of the agricultural diffusion research.
Other studies in the public health arena focused
on dissemination of new vaccines, family plan-
ning, and new medical technology.
Beginning in the late 1960s, there was a sub-
stantial increase in the amount of diffusion re-
search in three disciplines: business marketing,
communication, and transportation-technology
transfer. Marketing research principally address-
ed the characteristics of adopters of new products
and the role of opinion leaders in the adoption
process (Howes 1996). This literature is based
almost exclusively on commercial products, rang-
ing from coffee brands and soap to touch-tone
telephones, the personal computer, and internet
services. The studies tend to be largely atheoretical,
methodologically similar, and aimed simply at us-
ing knowledge of diffusion either to improve mar-
keting and sales of the product or to describe
product dissemination.
In sharp contrast, work done on innovation
diffusion by scholars trained in communication
has been considerably more theoretically orient-
ed. Throughout the 1960s, universities in America
began to establish separate departments of com-
munication (Rogers 1994). Since diffusion of inno-
vations was widely seen as one type of communica-
tion process, scholars in these new departments
adopted this type of research as one staple of their
work. Beginning with studies of the diffusion of
news events (Deutschmann and Danielson 1960),
this research tradition has branched out to study
the dissemination of a wide variety of specific
innovations (McQuail 1983, p. 194). Scholars work-
ing in this tradition have been principally responsi-
ble for the progressive refinements of formalized
theory of innovation diffusion. Everett Rogers has
consistently remained the leader in theory devel-
opment in communication, revising and extend-
ing his 1962 book Diffusion of Innovations with
help from co-author Floyd Shoemaker to pro-
duce Communication of Innovations in 1971. Subse-
quently, Rogers (1983, in press) restored the origi-
nal title Diffusion of Innovations, broadened the
theoretical base and incorporated diffusion stud-
ies and thinking from other disciplines. Gener-
ally, Rogers and other communication scholars
have studied the diffusion of many target materi-
al elements, phenomena, and other intangibles,
but they have continued to produce theoretical
statements dealing with communication channels,
diffusion networks, interpersonal influence and
the innovation-decision process. Finally, the tech-
nology dissemination and transfer issues have in-
volved work by geographers, engineers, and oth-
ers beginning in the 1970s. The primary focus of
such studies has been the spread or dissemina-
tion of technology (Sahal 1981) and the develop-
ment of network models of innovation diffusion
(Valente 1995).Theory in Innovation Diffusion. The theo-
retical work of Everett Rogers initially resulted in
the collection of knowledge gained from the rural
sociology tradition, then facilitated the transition
to communication perspectives, and now has served
as the mainstay of what is developing as a more
cross-disciplinary focus on innovation diffusion.
His contribution is twofold. First, he created in-
ventories of findings from many disciplines and
from many types of innovation. These inventories
provided impetus for the development of a defini-
tion of innovation diffusion that was not bound by
discipline. Second, Rogers assembled and refined
theoretical structures aimed at explaining the princi-
pal features of innovation diffusion. The theoreti-
cal work has cemented a core of knowledge and
principles that are widely identified (and used
empirically) as the bases of the diffusion of innova-
tions. Rogers’s (1983) theory includes eighty-one
generalizations (propositions) that have under-
gone empirical testing.The theory of innovation diffusion may be
understood as capturing the innovation-decision
process, innovation characteristics, adopter char-
acteristics, and opinion leadership. The innova-
tion-decision process represents the framework
on which diffusion research is built. It delineates
the process through which a decision maker (rep-
resenting any unit of analysis) chooses to adopt,
reinvent (modify), or reject an innovation. This
process consists of five stages. Knowledge is the
initial stage when the decision maker detects the
existence of the innovation and learns of its func-
tion. In the persuasion stage, the decision maker
forms a positive or negative attitude toward the
innovation. The third stage, decision, deals with the
decision-maker’s choice to accept or reject the