Q. What role is played by memory in consumer behavior ?
Learning involves a change in the content or else organization of long term memory and/or behaviour. The initial part of the definition focuses on what we know (and are able to thus put to use) while the subsequent focuses on concrete behaviour. For instance several people will avoid foods that they consumed shortly before becoming ill. Learning isn't all knowledge based. For instance we may experience the sales people in one store being nicer to us than those in the other. We therefore may develop a preference for the one store over the other but if pressed we mayn't be able to give a conscious explanation as to the reason for our preference.
Much early work on learning was in fact done on rats and other animals (and much of this research was unjustifiably cruel but that is another matter).