A. 1950s.

Reason: From 1940s- 1950s, a classical approach to the study of consumer behaviour was undertaken, which was highly criticised for the lack of mathematical proofs. Later on during 1950s, the subject gained even more relevance with the consumer being considered as a unit of analysis.During this time the focus of marketing with respect to understanding of the consumer behaviour shifted from economics, to other broader fields like behavioural sciences, sociology, anthropology and psychology. Other major additions were made to the research base of consumer behaviour during this time, such as impact of reference groups, brand loyalty and opinion leadership on consumer preferences and buying decisions.