Consumer decision making involves multiple stages. It begins with exposure to marketing messages which create product awareness and the recognition of needs. Consumers then gather information through search from both marketing efforts and their social environment. This information is processed using affective and cognitive evaluations of alternatives. A choice is made, followed by purchase behavior and later post-purchase evaluation. The amount of involvement and information search varies from routine, low involvement decisions to extensive decisions requiring significant research. The consumer decision making model has three stages - input, processing, and output.