Stern's Unplanned Purchase Concepts

He identified four types of unplanned purchases: Pure Impulse Buying, Reminder Impulse Buying, Suggestion Impulse Buying, Planned Impulse Buying. Even today, after 50 years, his concepts are starting point of new researches.
Over time, definition of impulse purchase has been revised. In 1987 Rook decided to bring elements of social science and phycology in his study to enhance understanding of impulse purchase. Unlike Clover, Rook suggested to look at customer characteristics and their personal traits rather than focusing on product characteristics. Moreover, Rook believed that, the term "impulse buying" refers to a narrower and more specific concept than "unplanned purchasing" does. He argued that, “it identifies a psychologically distinctive type of behavior that differs dramatically from contemplative modes of consumer choice”(Rook, 1987). Based on his finding, Rook suggested the following definition of impulse

It breaks the normal planned shopping pattern. Pure impulsive buying pattern is relatively rare. It is based on high emotional and spontaneous decisions. The way of avoidance such behavior can be pre-prepared shopping list, though even in this case consumers are often unable to resist strong urge of buying product.
➢ Reminder Impulsive Buying – it is a situation when consumer is exposed to the product and suddenly it will remind her/him about exhausted or low stock of this product at home. Exposition to the product may also help consumer to recall advertisement or other information about it and create desire to buy it now. Deterrent factor here can be previous negative experience with the product. Though, in case this experience was positive, it will spark impulse purchase even better.
➢ Suggestion Impulsive Buying – occurs when consumer is exposed to unknown product for the first time and it creates the feeling to him/her that she/he needs to try this product. Suggestion Impulsive Buying is different from Reminder Impulsive Buying with the fact that the consumer does not have any past experience with product. Hence, there is no any assistant for consumer to make decision. Product quality, function, and the like must be evaluated at the point of sale. In some cases, Suggestion Impulsive Buying can be considered as functional or rational purchase, which is in contrast to Pure Impulsive buying

These factors in some studies are referred as stimuli (Kotler 1974, Rook, 1987, Abratt, Goodey, 1990). Stimulus by its definition is something that incites a person to an action or reaction (Science dictionary, 2015). Researches identified number of different stimuli in their studies. Applebaum (1951) was the first, talking about promotional approaches in the store influencing and increasing impulsive behavior. Kotler (1974) gave priority to the atmospherics of the store. Bloch (1995) described impulsive buying as a result of hedonic instincts. Rook (1987) believed emotional cues were strong determinants for spontaneous purchase. Subsequent studies drew our attention to sensory factors, namely scent (Mattila and Wirtz, 2001) music, lighting, touch, taste. (Bakers et al.,