The decision making process consists of a sequence of five steps as illustrated below. It should be noted that each stage in the decision making process is not isolated but rather blends backwards into the preceding step and forwards into the subsequent step. Thus, the act of making a purchase is only a step within a process which actually began several processes before the final purchase is made.

Although consumers follow the decision-making steps when making some purchases, it must be noted however that this rational process does not accurately portray many purchase decisions, as consumers do not undertake this elaborate sequence every time they make a purchase. There are times when purchase decisions are made without prior planning, such as the impulsive purchase of chocolates at checkout whilst waiting to pay for groceries. 

Consumers do not necessarily follow the standard sequence of events and they could revert to any of the steps before making a final decision. 

In order to gain an understanding of the way of the way consumers make purchase decisions, a detailed understanding of the decision making process is required. The first step in the decision making process is the problem recognition step.

According to Schiffman and Kanuk, information from marketing and non-marketing sources feeds into the information-processing section of the model. After passing through the memory, which serves as a filter, the information has its initial influence at the need recognition stage.

Search for external information will be activated if additional information is required or if the consumer experiences dissonance because of dissatisfaction with the chosen alternative. The information processing section of the model consists of the consumer’s exposure, attention, comprehension, acceptance and retention of incoming information. The last section of the model consists of individual and environmental influences that affect all stages of the decision process.

Engel et al explain that consumers apply evaluative criteria such as the standards and specifications of products when comparing alternative brands. Evaluative criteria are the desired outcomes from purchase and consumption, and are expressed in the form of preferred attributes. They are shaped and influenced by individual differences and environmental influences. They are thus product-specific manifestations of an individual’s motives, values, and attitudes. The authors argue that consumers apply a four-stage process: first, they determine the evaluative criteria to use; second they decide which alternatives to consider; third, they assess the performance of the considered alternatives; and fourth, they select and apply a decision rule to make a final choice.

According to Engel et al, the complexity of alternative evaluation will vary dramatically depending on the particular process consumers follow in their consumption decisions. When decision-making is habitual in nature, alternative evaluation will, usually, simply involve the consumer forming an intention to repurchase the same product as before. However, sometimes alternative evaluation can be quite complex. Consumers may employ a number of different evaluative criteria, and these criteria will usually vary in their relative importance. The evaluative criteria used will depend on a host of situational, product, and individual factors.