Diffusion is the process of spreading out cultural patterns from one culture to another. The concept of diffusion was used first by Edward Tylor. He argued that most cultural parallels are the product of independent invention, but some are also the product of diffusion of cultural patterns. Cultural diffusion is only possible if two cultures are similar enough so the cultural pattern that is transmitted can take root in the new cultural environment. 

Diffusionism is a distinct theoretical approach in anthropology, and to a lesser extent, in sociology, that arose at the end of the 19th century as a reaction to the early theories of unilinear evolutionism. Diffusionism focuses on similarities of cultural patterns among cultures, hypothesizing that those similarities are the result of a process of diffusion, that is, the spread of cultural patterns from one culture to another. There are three types of diffusion theories: hyper-diffusionism, moderate diffusionism, and cultural circles (areas) approach.

The English anthropologists W. J. Perry and Elliot Smith devised hyper-diffusionism. They held that human culture originated in Egypt and that from about 4000 BC progressively diffused to all other cultures and civilizations all over the earth. This approach is, also, often called the” pan-Egyptian”, “heliolithic”, or “heliocentric” school.

German authors Fritz Graebner, Leo Frobenius, and Wilhelm Schmidt, who were members of the historical school in Germany, identified primeval culture complexes, or culture circles (kulturkreise). Their historicist approach postulated that critical aspects of cultures originated in a small number of geographically isolated societies. They also studied cultural archetypes and patterns in world history. American anthropologist Clark Wissler (1929), in a similar vein, identified, based on empirical evidence,  ten „culture areas“ that were created by cultural diffusion in North and South America and the Caribbean.

American anthropologists Franz Boas, Alfred Kroeber, and Robert Lowie developed a position called moderate diffusionism, that allowed for the coexistence of multiple mechanisms of cultural change and transfer. In addition to diffusion, there are also processes of independent invention, acculturation, and others.

At the same time, French sociologist Gabriel Tarde started studying the diffusion of innovations, not across societies and cultures, but in one society. Although Tarde didn’t use the term diffusion, he examined the role of innovation adopters and the social influence of the spread of innovations. Tarde, in lue of diffusion used the term imitaition. He extended the process of imitation to the whole of society and thus came to methodological individualism which serves as the basis for his macro-social theory. Tarde explains social phenomena by permanent, socially shaped, psychological predispositions. Innovations occur in certain social groups and then spread further through social groups, and then to the whole society. If there were no social barriers, innovation would spread quickly and evenly, but in real situations, there are always barriers. The speed and patterns of the spread of innovation depend on these social circumstances.

Individuals, themselves, are not able to resist this spread, but fall under the influence of social groups with which they are connected by interactions. There is a difference, between rural and urban areas, in the way innovations are spreading. In the city, innovations spread like fashion, and when they reach the countryside, innovations are maintained through imitation, which has the form of a habit. Tarde singles out pride, closeness, and racial and class prejudice as psychological barriers to the spread of innovation. Psychological barriers especially reflect social divisions and inequalities. Political power has a special influence, because individuals imitate those who have more power, and avoid imitating those less powerful than themselves. Social consensus is formed when the attitudes adopted by the elite are extended to the whole society. Once the process of spreading innovation begins, it spreads with geometric progression. The spread of social consensus to the whole society is limited by barriers in communication, as well as in situations in which a large number of people find themselves in a crowd because then people reject the views of the politically more powerful and accept the views of those like them.

Leslie White notes the importance of the diffusion of cultural patterns, which means that not every single culture has to go through all the stages, because, due to the process of diffusion, some stages may be skipped. Marvin Harris believes that the explanation for the development of agriculture cannot be found in the diffusion of innovations from a single center, nor in some increase in inventiveness. 

Diffusion of Innovations and Technology in Modern Society

Everett Rogers is best known for the theory he presented in his book Diffusion of Innovation (1962), and the book has been published in four other supplemented editions. His theory of the diffusion of innovation explains the process by which innovation spreads from the moment it is created, until the moment it becomes fully accepted. Rogers has researched the processes and contextual factors that influence the speed of adoption or rejection of innovations.

He introduced two new categories - early and late adopters. The focus was on the spread of commercial innovation in the modern age, so a lot of attention was paid to the commercialization and advertising of innovations. The center adopts innovations faster than the periphery. Rogers developed a two-step communication theory to explain how information about innovation spreads. At the first level, information about the innovation is created, as well as advertising materials about it. At the second level, people in charge of product promotion go to targeted communities and approach those who are considered potential buyers of innovation. The promoters then offer free product testing to those who are targeted. Finally, these early adopters of innovation influence their acquaintances to adopt the innovation as well.

Rogers concluded that the adoption of innovations over time has a standard variation (Bell curve). He singled out five types of technology adopters, in relation to the chronology of innovation acceptance: innovators (2.5%), early adopters (13.5%), early majority (34%), late majority (34%), and laggards (16 %). Rogers later applied his theory of innovation and communication to the areas of family planning, media expansion, and cancer prevention. The fifth edition of Diffusion of Innovation (2003, with Nancy Singer Olaguera) explores how the Internet spread, changes in communication, and the spread of ideas that it has brought.

William Ogburn states that the process of technological change goes through four phases: invention, accumulation, diffusion, and adjustment. The invention is the process of creating new technology. New technologies emerge only when there are sufficient levels of knowledge and technology in an area. Accumulation is the process of increasing the total number of technologies used at the same time, in a society. Diffusion is the expansion of technologies between two societies or cultures. Adjustment is the last phase in which non-technological aspects of culture are adapted to inventions. Ogburn calls periods in which changes in other spheres have not yet been harmonized with technological changes periods of "maladaptation". Ogburn's theory of cultural and social change contains aspects of technological determinism, not only because it pays the most attention to technology, which causes a change in other areas, but also because it pays little attention to great historical events or influential individuals.

References:

Albrow. The Global Age: State and Society Beyond Modernity (1996);

Foucault. Histoire de la sexualité, vol. 1: La volonté de savoir (1976);

     -     Histoire de la sexualité, vol. 2: L'usage des plaisirs (1984a);

     -     Histoire de la sexualité, vol. 3: Le souci de soi (1984b);

Lenski. Ecological-Evolutionary Theory (2006).

Ogburn. Social Change with Respect to Culture and Original Nature (1922);

Rogers. Diffusion of Innovations (1962);

     -     Diffusion of Innovation, fifth ed. (2003). 

Sutherland. „The Diffusion of the Sexual Psychopath Laws”, in American Journal of Sociology (1950); 

Tarde. Social Laws - an Outline of Sociology (1899, in French 1898b);  

The Laws of Imitation (2013, in French (1890);

Thomas W. Old World Traits Transplanted (1921).