Cultural invention has come to mean any innovation that is new and found to be useful to a group of people and expressed in their behavior but which does not exist as a physical object. Humanity is in a global "accelerating culture change period", driven by the expansion of international commerce, the mass media, and above all, the human population explosion, among other factors.
Cultures are internally affected by both forces encouraging change and forces resisting change. These forces are related to both social structures and natural events, and are involved in the perpetuation of cultural ideas and practices within current structures, which themselves are subject to change.
Social conflict and the development of technologies can produce changes within a society by altering social dynamics and promoting new cultural models, and spurring or enabling generative action. These social shifts may accompany ideological shifts and other types of cultural change. For example, the U.S. feminist movement involved new practices that produced a shift in gender relations, altering both gender and economic structures. Environmental conditions may also enter as factors. For example, after tropical forests returned at the end of the last ice age, plants suitable for domestication were available, leading to the invention of agriculture, which in turn brought about many cultural innovations and shifts in social dynamics.
Full-length profile portrait of Turkman woman, standing on a carpet at the entrance to a yurt, dressed in traditional clothing and jewelry
Cultures are externally affected via contact between societies, which may also produce—or inhibit—social shifts and changes in cultural practices. War or competition over resources may impact technological development or social dynamics. Additionally, cultural ideas may transfer from one society to another, through diffusion or acculturation. In diffusion, the form of something (though not necessarily its meaning) moves from one culture to another. For example, hamburgers, mundane in the United States, seemed exotic when introduced into China. "Stimulus diffusion" (the sharing of ideas) refers to an element of one culture leading to an invention or propagation in another. "Direct Borrowing" on the other hand tends to refer to technological or tangible diffusion from one culture to another. Diffusion of innovations theory presents a research-based model of why and when individuals and cultures adopt new ideas, practices, and products.
Acculturation has different meanings, but in this context refers to replacement of the traits of one culture with those of another, such has happened to certain Native American tribes and to many indigenous peoples across the globe during the process of colonization. Related processes on an individual level include assimilation (adoption of a different culture by an individual) and transculturation.