I. Meaning of Diffusion: Social change occurs through cultural contact between different societies. Diffusion is an important mechanism of social change. One society adopts the cultural traits of another through prolonged contact as in travel, trade and commerce as also through sudden events like war where new and hitherto secret technologies reveal themselves.

II. The Role of diffusion as a means of Social Change: 

(i) Cultural mores as well as new technology are borrowed and adopted when societies find that they fill a vacuum or answer a felt need. Borrowing of cultural traits from an advanced society is commonly seen in developing countries and societies as they try to become modern. Diffusion of cultural traits also takes place through personal contacts and interaction between members of two or more cultures. This can be seen in the changes that crept in Indian society due to sustained contacts with Greeks, Muslims and the British. Indian music and architecture was greatly influenced by Islam.

(ii) New schools like khayal developed due to the influence of Persian music and new instruments like tabla and sitar. In architecture, the Indo-Saracenic style appeared with spacious interiors, massive domes, arches and minarets. Sufism was highly influenced by the mysticism of Hindus, while the monotheistic ideas of Islam influenced Hindu society, particularly some leaders of the Bhakti movement like Kabir.

(iii) Diffusion also takes place through mass media as it transmits and diffuses information to a large number of people. It has accelerated the process of change by spreading the elements of individual cultures to people far away and thus resulted in a form of cultural modernisation. This synthesis results in a new form of culture, which has elements of both the traditional and the modern. Folk songs and western music have combined to create a new style of popular music.

(iv) It is, however, interesting to note that while cultural diffusion quickly changed the material life of people, non-material aspects like religion, ideology and beliefs are slow to change. 

(v) This phenomenon is known as "cultural Iag". When non-material culture does not adjust itself readily to the material changes, it results in a lag between the two. The problem of adjustment in modern societies can be explained by this concept where the material aspects of life change at a much quicker pace than the non-material aspects of culture. All societies need to manage this culture. Societies where the non-material aspects of culture guide material changes towards peace and social harmony are likely to see more progress than others.