Cognitive model and behavioural model are two of the most common approaches that have been using by the marketers to understand consumer behaviour. Both approaches have their own supporters who are the theorists or marketers. However, there has been an argument that about which model describes the consumer behaviour the best existed in markets for decades.
"Consumer behavior is widely understood as a problem-solving and decision-making sequence, the outcome of which is determined by the buyer's goal-directed processing of information." (Foxall 1992, p384). Cognitive model describes the consumers go through a few processes that consist of a few steps to achieve their purchase decisions among some alternatives. It is the most common and well known school of thought. Although cognitive model sounds make sense and persuasive, it does not really has empirical facts to prove that it really works in all the real market.
In other words, although this purchase model has explanatory power, it does not have predictive power. It is hard to predict the consumers purchase decision since everyone has their own reasons to purchase. For example, some people buy a vase for decoration and some people buy it for putting flower. This is the often model that has been use to fill in the blank of marketer's mind. This school of thought emphasize on the reasons of purchase decision is made. According to cognitive model, the advertisement of the product must be factual since the consumers will spend time and effort to do some survey, research or analysis about the product. However, cognitive model do exist in the real market world in some buying situations.